- 16 1月, 2016 8 次提交
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由 Vladimir Davydov 提交于
page_referenced_one() and page_idle_clear_pte_refs_one() duplicate the code for looking up pte of a (possibly transhuge) page. Move this code to a new helper function, page_check_address_transhuge(), and make the above mentioned functions use it. This is just a cleanup, no functional changes are intended. Signed-off-by: NVladimir Davydov <vdavydov@virtuozzo.com> Reviewed-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Kirill A. Shutemov 提交于
Both page_referenced() and page_idle_clear_pte_refs_one() assume that THP can only be mapped with PMD, so there's no reason to look on PTEs for PageTransHuge() pages. That's no true anymore: THP can be mapped with PTEs too. The patch removes PageTransHuge() test from the functions and opencode page table check. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Kirill A. Shutemov 提交于
Before THP refcounting rework, THP was not allowed to cross VMA boundary. So, if we have THP and we split it, PG_mlocked can be safely transferred to small pages. With new THP refcounting and naive approach to mlocking we can end up with this scenario: 1. we have a mlocked THP, which belong to one VM_LOCKED VMA. 2. the process does munlock() on the *part* of the THP: - the VMA is split into two, one of them VM_LOCKED; - huge PMD split into PTE table; - THP is still mlocked; 3. split_huge_page(): - it transfers PG_mlocked to *all* small pages regrardless if it blong to any VM_LOCKED VMA. We probably could munlock() all small pages on split_huge_page(), but I think we have accounting issue already on step two. Instead of forbidding mlocked pages altogether, we just avoid mlocking PTE-mapped THPs and munlock THPs on split_huge_pmd(). This means PTE-mapped THPs will be on normal lru lists and will be split under memory pressure by vmscan. After the split vmscan will detect unevictable small pages and mlock them. With this approach we shouldn't hit situation like described above. Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Steve Capper <steve.capper@linaro.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Kirill A. Shutemov 提交于
Currently we don't split huge page on partial unmap. It's not an ideal situation. It can lead to memory overhead. Furtunately, we can detect partial unmap on page_remove_rmap(). But we cannot call split_huge_page() from there due to locking context. It's also counterproductive to do directly from munmap() codepath: in many cases we will hit this from exit(2) and splitting the huge page just to free it up in small pages is not what we really want. The patch introduce deferred_split_huge_page() which put the huge page into queue for splitting. The splitting itself will happen when we get memory pressure via shrinker interface. The page will be dropped from list on freeing through compound page destructor. Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com> Tested-by: NSasha Levin <sasha.levin@oracle.com> Tested-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Acked-by: NVlastimil Babka <vbabka@suse.cz> Acked-by: NJerome Marchand <jmarchan@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Steve Capper <steve.capper@linaro.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Kirill A. Shutemov 提交于
This patch adds implementation of split_huge_page() for new refcountings. Unlike previous implementation, new split_huge_page() can fail if somebody holds GUP pin on the page. It also means that pin on page would prevent it from bening split under you. It makes situation in many places much cleaner. The basic scheme of split_huge_page(): - Check that sum of mapcounts of all subpage is equal to page_count() plus one (caller pin). Foll off with -EBUSY. This way we can avoid useless PMD-splits. - Freeze the page counters by splitting all PMD and setup migration PTEs. - Re-check sum of mapcounts against page_count(). Page's counts are stable now. -EBUSY if page is pinned. - Split compound page. - Unfreeze the page by removing migration entries. Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com> Tested-by: NSasha Levin <sasha.levin@oracle.com> Tested-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Acked-by: NJerome Marchand <jmarchan@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Steve Capper <steve.capper@linaro.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Kirill A. Shutemov 提交于
We're going to allow mapping of individual 4k pages of THP compound. It means we need to track mapcount on per small page basis. Straight-forward approach is to use ->_mapcount in all subpages to track how many time this subpage is mapped with PMDs or PTEs combined. But this is rather expensive: mapping or unmapping of a THP page with PMD would require HPAGE_PMD_NR atomic operations instead of single we have now. The idea is to store separately how many times the page was mapped as whole -- compound_mapcount. This frees up ->_mapcount in subpages to track PTE mapcount. We use the same approach as with compound page destructor and compound order to store compound_mapcount: use space in first tail page, ->mapping this time. Any time we map/unmap whole compound page (THP or hugetlb) -- we increment/decrement compound_mapcount. When we map part of compound page with PTE we operate on ->_mapcount of the subpage. page_mapcount() counts both: PTE and PMD mappings of the page. Basically, we have mapcount for a subpage spread over two counters. It makes tricky to detect when last mapcount for a page goes away. We introduced PageDoubleMap() for this. When we split THP PMD for the first time and there's other PMD mapping left we offset up ->_mapcount in all subpages by one and set PG_double_map on the compound page. These additional references go away with last compound_mapcount. This approach provides a way to detect when last mapcount goes away on per small page basis without introducing new overhead for most common cases. [akpm@linux-foundation.org: fix typo in comment] [mhocko@suse.com: ignore partial THP when moving task] Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com> Tested-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Acked-by: NJerome Marchand <jmarchan@redhat.com> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Steve Capper <steve.capper@linaro.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NMichal Hocko <mhocko@suse.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Kirill A. Shutemov 提交于
With new refcounting we don't need to mark PMDs splitting. Let's drop code to handle this. Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com> Tested-by: NSasha Levin <sasha.levin@oracle.com> Tested-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Acked-by: NVlastimil Babka <vbabka@suse.cz> Acked-by: NJerome Marchand <jmarchan@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Steve Capper <steve.capper@linaro.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Kirill A. Shutemov 提交于
We're going to allow mapping of individual 4k pages of THP compound page. It means we cannot rely on PageTransHuge() check to decide if map/unmap small page or THP. The patch adds new argument to rmap functions to indicate whether we want to operate on whole compound page or only the small page. [n-horiguchi@ah.jp.nec.com: fix mapcount mismatch in hugepage migration] Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com> Tested-by: NSasha Levin <sasha.levin@oracle.com> Tested-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Acked-by: NVlastimil Babka <vbabka@suse.cz> Acked-by: NJerome Marchand <jmarchan@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Steve Capper <steve.capper@linaro.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 15 1月, 2016 2 次提交
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由 Jerome Marchand 提交于
Currently looking at /proc/<pid>/status or statm, there is no way to distinguish shmem pages from pages mapped to a regular file (shmem pages are mapped to /dev/zero), even though their implication in actual memory use is quite different. The internal accounting currently counts shmem pages together with regular files. As a preparation to extend the userspace interfaces, this patch adds MM_SHMEMPAGES counter to mm_rss_stat to account for shmem pages separately from MM_FILEPAGES. The next patch will expose it to userspace - this patch doesn't change the exported values yet, by adding up MM_SHMEMPAGES to MM_FILEPAGES at places where MM_FILEPAGES was used before. The only user-visible change after this patch is the OOM killer message that separates the reported "shmem-rss" from "file-rss". [vbabka@suse.cz: forward-porting, tweak changelog] Signed-off-by: NJerome Marchand <jmarchan@redhat.com> Signed-off-by: NVlastimil Babka <vbabka@suse.cz> Acked-by: NKonstantin Khlebnikov <khlebnikov@yandex-team.ru> Acked-by: NMichal Hocko <mhocko@suse.com> Acked-by: NHugh Dickins <hughd@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Vladimir Davydov 提交于
Mark those kmem allocations that are known to be easily triggered from userspace as __GFP_ACCOUNT/SLAB_ACCOUNT, which makes them accounted to memcg. For the list, see below: - threadinfo - task_struct - task_delay_info - pid - cred - mm_struct - vm_area_struct and vm_region (nommu) - anon_vma and anon_vma_chain - signal_struct - sighand_struct - fs_struct - files_struct - fdtable and fdtable->full_fds_bits - dentry and external_name - inode for all filesystems. This is the most tedious part, because most filesystems overwrite the alloc_inode method. The list is far from complete, so feel free to add more objects. Nevertheless, it should be close to "account everything" approach and keep most workloads within bounds. Malevolent users will be able to breach the limit, but this was possible even with the former "account everything" approach (simply because it did not account everything in fact). [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: NVladimir Davydov <vdavydov@virtuozzo.com> Acked-by: NJohannes Weiner <hannes@cmpxchg.org> Acked-by: NMichal Hocko <mhocko@suse.com> Cc: Tejun Heo <tj@kernel.org> Cc: Greg Thelen <gthelen@google.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 06 11月, 2015 4 次提交
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由 Hugh Dickins 提交于
Hitherto page migration has avoided using a migration entry for a swapcache page mapped into userspace, apparently for historical reasons. So any page blessed with swapcache would entail a minor fault when it's next touched, which page migration otherwise tries to avoid. Swapcache in an mlocked area is rare, so won't often matter, but still better fixed. Just rearrange the block in try_to_unmap_one(), to handle TTU_MIGRATION before checking PageAnon, that's all (apart from some reindenting). Well, no, that's not quite all: doesn't this by the way fix a soft_dirty bug, that page migration of a file page was forgetting to transfer the soft_dirty bit? Probably not a serious bug: if I understand correctly, soft_dirty afficionados usually have to handle file pages separately anyway; but we publish the bit in /proc/<pid>/pagemap on file mappings as well as anonymous, so page migration ought not to perturb it. Signed-off-by: NHugh Dickins <hughd@google.com> Cc: Christoph Lameter <cl@linux.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Rik van Riel <riel@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: NCyrill Gorcunov <gorcunov@openvz.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Hugh Dickins 提交于
KernelThreadSanitizer (ktsan) has shown that the down_read_trylock() of mmap_sem in try_to_unmap_one() (when going to set PageMlocked on a page found mapped in a VM_LOCKED vma) is ineffective against races with exit_mmap()'s munlock_vma_pages_all(), because mmap_sem is not held when tearing down an mm. But that's okay, those races are benign; and although we've believed for years in that ugly down_read_trylock(), it's unsuitable for the job, and frustrates the good intention of setting PageMlocked when it fails. It just doesn't matter if here we read vm_flags an instant before or after a racing mlock() or munlock() or exit_mmap() sets or clears VM_LOCKED: the syscalls (or exit) work their way up the address space (taking pt locks after updating vm_flags) to establish the final state. We do still need to be careful never to mark a page Mlocked (hence unevictable) by any race that will not be corrected shortly after. The page lock protects from many of the races, but not all (a page is not necessarily locked when it's unmapped). But the pte lock we just dropped is good to cover the rest (and serializes even with munlock_vma_pages_all(), so no special barriers required): now hold on to the pte lock while calling mlock_vma_page(). Is that lock ordering safe? Yes, that's how follow_page_pte() calls it, and how page_remove_rmap() calls the complementary clear_page_mlock(). This fixes the following case (though not a case which anyone has complained of), which mmap_sem did not: truncation's preliminary unmap_mapping_range() is supposed to remove even the anonymous COWs of filecache pages, and that might race with try_to_unmap_one() on a VM_LOCKED vma, so that mlock_vma_page() sets PageMlocked just after zap_pte_range() unmaps the page, causing "Bad page state (mlocked)" when freed. The pte lock protects against this. You could say that it also protects against the more ordinary case, racing with the preliminary unmapping of a filecache page itself: but in our current tree, that's independently protected by i_mmap_rwsem; and that race would be why "Bad page state (mlocked)" was seen before commit 48ec833b ("Revert mm/memory.c: share the i_mmap_rwsem"). Vlastimil Babka points out another race which this patch protects against. try_to_unmap_one() might reach its mlock_vma_page() TestSetPageMlocked a moment after munlock_vma_pages_all() did its Phase 1 TestClearPageMlocked: leaving PageMlocked and unevictable when it should be evictable. mmap_sem is ineffective because exit_mmap() does not hold it; page lock ineffective because __munlock_pagevec() only takes it afterwards, in Phase 2; pte lock is effective because __munlock_pagevec_fill() takes it to get the page, after VM_LOCKED was cleared from vm_flags, so visible to try_to_unmap_one. Kirill Shutemov points out that if the compiler chooses to implement a "vma->vm_flags &= VM_WHATEVER" or "vma->vm_flags |= VM_WHATEVER" operation with an intermediate store of unrelated bits set, since I'm here foregoing its usual protection by mmap_sem, try_to_unmap_one() might catch sight of a spurious VM_LOCKED in vm_flags, and make the wrong decision. This does not appear to be an immediate problem, but we may want to define vm_flags accessors in future, to guard against such a possibility. While we're here, make a related optimization in try_to_munmap_one(): if it's doing TTU_MUNLOCK, then there's no point at all in descending the page tables and getting the pt lock, unless the vma is VM_LOCKED. Yes, that can change racily, but it can change racily even without the optimization: it's not critical. Far better not to waste time here. Stopped short of separating try_to_munlock_one() from try_to_munmap_one() on this occasion, but that's probably the sensible next step - with a rename, given that try_to_munlock()'s business is to try to set Mlocked. Updated the unevictable-lru Documentation, to remove its reference to mmap semaphore, but found a few more updates needed in just that area. Signed-off-by: NHugh Dickins <hughd@google.com> Cc: Christoph Lameter <cl@linux.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Rik van Riel <riel@redhat.com> Acked-by: NVlastimil Babka <vbabka@suse.cz> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Andrea Arcangeli 提交于
While at it add it to the file and anon walks too. Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com> Acked-by: NHugh Dickins <hughd@google.com> Cc: Petr Holasek <pholasek@redhat.com> Acked-by: NDavidlohr Bueso <dbueso@suse.de> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Naoya Horiguchi 提交于
Currently there's no easy way to get per-process usage of hugetlb pages, which is inconvenient because userspace applications which use hugetlb typically want to control their processes on the basis of how much memory (including hugetlb) they use. So this patch simply provides easy access to the info via /proc/PID/status. Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com> Acked-by: NJoern Engel <joern@logfs.org> Acked-by: NDavid Rientjes <rientjes@google.com> Acked-by: NMichal Hocko <mhocko@suse.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 11 9月, 2015 1 次提交
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由 Vladimir Davydov 提交于
Knowing the portion of memory that is not used by a certain application or memory cgroup (idle memory) can be useful for partitioning the system efficiently, e.g. by setting memory cgroup limits appropriately. Currently, the only means to estimate the amount of idle memory provided by the kernel is /proc/PID/{clear_refs,smaps}: the user can clear the access bit for all pages mapped to a particular process by writing 1 to clear_refs, wait for some time, and then count smaps:Referenced. However, this method has two serious shortcomings: - it does not count unmapped file pages - it affects the reclaimer logic To overcome these drawbacks, this patch introduces two new page flags, Idle and Young, and a new sysfs file, /sys/kernel/mm/page_idle/bitmap. A page's Idle flag can only be set from userspace by setting bit in /sys/kernel/mm/page_idle/bitmap at the offset corresponding to the page, and it is cleared whenever the page is accessed either through page tables (it is cleared in page_referenced() in this case) or using the read(2) system call (mark_page_accessed()). Thus by setting the Idle flag for pages of a particular workload, which can be found e.g. by reading /proc/PID/pagemap, waiting for some time to let the workload access its working set, and then reading the bitmap file, one can estimate the amount of pages that are not used by the workload. The Young page flag is used to avoid interference with the memory reclaimer. A page's Young flag is set whenever the Access bit of a page table entry pointing to the page is cleared by writing to the bitmap file. If page_referenced() is called on a Young page, it will add 1 to its return value, therefore concealing the fact that the Access bit was cleared. Note, since there is no room for extra page flags on 32 bit, this feature uses extended page flags when compiled on 32 bit. [akpm@linux-foundation.org: fix build] [akpm@linux-foundation.org: kpageidle requires an MMU] [akpm@linux-foundation.org: decouple from page-flags rework] Signed-off-by: NVladimir Davydov <vdavydov@parallels.com> Reviewed-by: NAndres Lagar-Cavilla <andreslc@google.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Michel Lespinasse <walken@google.com> Cc: David Rientjes <rientjes@google.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 05 9月, 2015 2 次提交
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由 Mel Gorman 提交于
If a PTE is unmapped and it's dirty then it was writable recently. Due to deferred TLB flushing, it's best to assume a writable TLB cache entry exists. With that assumption, the TLB must be flushed before any IO can start or the page is freed to avoid lost writes or data corruption. This patch defers flushing of potentially writable TLBs as long as possible. Signed-off-by: NMel Gorman <mgorman@suse.de> Reviewed-by: NRik van Riel <riel@redhat.com> Cc: Dave Hansen <dave.hansen@intel.com> Acked-by: NIngo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Mel Gorman 提交于
An IPI is sent to flush remote TLBs when a page is unmapped that was potentially accesssed by other CPUs. There are many circumstances where this happens but the obvious one is kswapd reclaiming pages belonging to a running process as kswapd and the task are likely running on separate CPUs. On small machines, this is not a significant problem but as machine gets larger with more cores and more memory, the cost of these IPIs can be high. This patch uses a simple structure that tracks CPUs that potentially have TLB entries for pages being unmapped. When the unmapping is complete, the full TLB is flushed on the assumption that a refill cost is lower than flushing individual entries. Architectures wishing to do this must give the following guarantee. If a clean page is unmapped and not immediately flushed, the architecture must guarantee that a write to that linear address from a CPU with a cached TLB entry will trap a page fault. This is essentially what the kernel already depends on but the window is much larger with this patch applied and is worth highlighting. The architecture should consider whether the cost of the full TLB flush is higher than sending an IPI to flush each individual entry. An additional architecture helper called flush_tlb_local is required. It's a trivial wrapper with some accounting in the x86 case. The impact of this patch depends on the workload as measuring any benefit requires both mapped pages co-located on the LRU and memory pressure. The case with the biggest impact is multiple processes reading mapped pages taken from the vm-scalability test suite. The test case uses NR_CPU readers of mapped files that consume 10*RAM. Linear mapped reader on a 4-node machine with 64G RAM and 48 CPUs 4.2.0-rc1 4.2.0-rc1 vanilla flushfull-v7 Ops lru-file-mmap-read-elapsed 159.62 ( 0.00%) 120.68 ( 24.40%) Ops lru-file-mmap-read-time_range 30.59 ( 0.00%) 2.80 ( 90.85%) Ops lru-file-mmap-read-time_stddv 6.70 ( 0.00%) 0.64 ( 90.38%) 4.2.0-rc1 4.2.0-rc1 vanilla flushfull-v7 User 581.00 611.43 System 5804.93 4111.76 Elapsed 161.03 122.12 This is showing that the readers completed 24.40% faster with 29% less system CPU time. From vmstats, it is known that the vanilla kernel was interrupted roughly 900K times per second during the steady phase of the test and the patched kernel was interrupts 180K times per second. The impact is lower on a single socket machine. 4.2.0-rc1 4.2.0-rc1 vanilla flushfull-v7 Ops lru-file-mmap-read-elapsed 25.33 ( 0.00%) 20.38 ( 19.54%) Ops lru-file-mmap-read-time_range 0.91 ( 0.00%) 1.44 (-58.24%) Ops lru-file-mmap-read-time_stddv 0.28 ( 0.00%) 0.47 (-65.34%) 4.2.0-rc1 4.2.0-rc1 vanilla flushfull-v7 User 58.09 57.64 System 111.82 76.56 Elapsed 27.29 22.55 It's still a noticeable improvement with vmstat showing interrupts went from roughly 500K per second to 45K per second. The patch will have no impact on workloads with no memory pressure or have relatively few mapped pages. It will have an unpredictable impact on the workload running on the CPU being flushed as it'll depend on how many TLB entries need to be refilled and how long that takes. Worst case, the TLB will be completely cleared of active entries when the target PFNs were not resident at all. [sasha.levin@oracle.com: trace tlb flush after disabling preemption in try_to_unmap_flush] Signed-off-by: NMel Gorman <mgorman@suse.de> Reviewed-by: NRik van Riel <riel@redhat.com> Cc: Dave Hansen <dave.hansen@intel.com> Acked-by: NIngo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: NSasha Levin <sasha.levin@oracle.com> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 25 6月, 2015 2 次提交
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由 Aneesh Kumar K.V 提交于
We have confusing functions to clear pmd, pmd_clear_* and pmd_clear. Add _huge_ to pmdp_clear functions so that we are clear that they operate on hugepage pte. We don't bother about other functions like pmdp_set_wrprotect, pmdp_clear_flush_young, because they operate on PTE bits and hence indicate they are operating on hugepage ptes Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Vladimir Davydov 提交于
As noted by Paul the compiler is free to store a temporary result in a variable on stack, heap or global unless it is explicitly marked as volatile, see: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4455.html#sample-optimizations This can result in a race between do_wp_page() and shrink_active_list() as follows. In do_wp_page() we can call page_move_anon_rmap(), which sets page->mapping as follows: anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; page->mapping = (struct address_space *) anon_vma; The page in question may be on an LRU list, because nowhere in do_wp_page() we remove it from the list, neither do we take any LRU related locks. Although the page is locked, shrink_active_list() can still call page_referenced() on it concurrently, because the latter does not require an anonymous page to be locked: CPU0 CPU1 ---- ---- do_wp_page shrink_active_list lock_page page_referenced PageAnon->yes, so skip trylock_page page_move_anon_rmap page->mapping = anon_vma rmap_walk PageAnon->no rmap_walk_file BUG page->mapping += PAGE_MAPPING_ANON This patch fixes this race by explicitly forbidding the compiler to split page->mapping store in page_move_anon_rmap() with the aid of WRITE_ONCE. [akpm@linux-foundation.org: tweak comment, per Minchan] Signed-off-by: NVladimir Davydov <vdavydov@parallels.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: NRik van Riel <riel@redhat.com> Cc: Hugh Dickins <hughd@google.com> Acked-by: NMinchan Kim <minchan@kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 02 6月, 2015 1 次提交
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由 Greg Thelen 提交于
When modifying PG_Dirty on cached file pages, update the new MEM_CGROUP_STAT_DIRTY counter. This is done in the same places where global NR_FILE_DIRTY is managed. The new memcg stat is visible in the per memcg memory.stat cgroupfs file. The most recent past attempt at this was http://thread.gmane.org/gmane.linux.kernel.cgroups/8632 The new accounting supports future efforts to add per cgroup dirty page throttling and writeback. It also helps an administrator break down a container's memory usage and provides evidence to understand memcg oom kills (the new dirty count is included in memcg oom kill messages). The ability to move page accounting between memcg (memory.move_charge_at_immigrate) makes this accounting more complicated than the global counter. The existing mem_cgroup_{begin,end}_page_stat() lock is used to serialize move accounting with stat updates. Typical update operation: memcg = mem_cgroup_begin_page_stat(page) if (TestSetPageDirty()) { [...] mem_cgroup_update_page_stat(memcg) } mem_cgroup_end_page_stat(memcg) Summary of mem_cgroup_end_page_stat() overhead: - Without CONFIG_MEMCG it's a no-op - With CONFIG_MEMCG and no inter memcg task movement, it's just rcu_read_lock() - With CONFIG_MEMCG and inter memcg task movement, it's rcu_read_lock() + spin_lock_irqsave() A memcg parameter is added to several routines because their callers now grab mem_cgroup_begin_page_stat() which returns the memcg later needed by for mem_cgroup_update_page_stat(). Because mem_cgroup_begin_page_stat() may disable interrupts, some adjustments are needed: - move __mark_inode_dirty() from __set_page_dirty() to its caller. __mark_inode_dirty() locking does not want interrupts disabled. - use spin_lock_irqsave(tree_lock) rather than spin_lock_irq() in __delete_from_page_cache(), replace_page_cache_page(), invalidate_complete_page2(), and __remove_mapping(). text data bss dec hex filename 8925147 1774832 1785856 12485835 be84cb vmlinux-!CONFIG_MEMCG-before 8925339 1774832 1785856 12486027 be858b vmlinux-!CONFIG_MEMCG-after +192 text bytes 8965977 1784992 1785856 12536825 bf4bf9 vmlinux-CONFIG_MEMCG-before 8966750 1784992 1785856 12537598 bf4efe vmlinux-CONFIG_MEMCG-after +773 text bytes Performance tests run on v4.0-rc1-36-g4f671fe2. Lower is better for all metrics, they're all wall clock or cycle counts. The read and write fault benchmarks just measure fault time, they do not include I/O time. * CONFIG_MEMCG not set: baseline patched kbuild 1m25.030000(+-0.088% 3 samples) 1m25.426667(+-0.120% 3 samples) dd write 100 MiB 0.859211561 +-15.10% 0.874162885 +-15.03% dd write 200 MiB 1.670653105 +-17.87% 1.669384764 +-11.99% dd write 1000 MiB 8.434691190 +-14.15% 8.474733215 +-14.77% read fault cycles 254.0(+-0.000% 10 samples) 253.0(+-0.000% 10 samples) write fault cycles 2021.2(+-3.070% 10 samples) 1984.5(+-1.036% 10 samples) * CONFIG_MEMCG=y root_memcg: baseline patched kbuild 1m25.716667(+-0.105% 3 samples) 1m25.686667(+-0.153% 3 samples) dd write 100 MiB 0.855650830 +-14.90% 0.887557919 +-14.90% dd write 200 MiB 1.688322953 +-12.72% 1.667682724 +-13.33% dd write 1000 MiB 8.418601605 +-14.30% 8.673532299 +-15.00% read fault cycles 266.0(+-0.000% 10 samples) 266.0(+-0.000% 10 samples) write fault cycles 2051.7(+-1.349% 10 samples) 2049.6(+-1.686% 10 samples) * CONFIG_MEMCG=y non-root_memcg: baseline patched kbuild 1m26.120000(+-0.273% 3 samples) 1m25.763333(+-0.127% 3 samples) dd write 100 MiB 0.861723964 +-15.25% 0.818129350 +-14.82% dd write 200 MiB 1.669887569 +-13.30% 1.698645885 +-13.27% dd write 1000 MiB 8.383191730 +-14.65% 8.351742280 +-14.52% read fault cycles 265.7(+-0.172% 10 samples) 267.0(+-0.000% 10 samples) write fault cycles 2070.6(+-1.512% 10 samples) 2084.4(+-2.148% 10 samples) As expected anon page faults are not affected by this patch. tj: Updated to apply on top of the recent cancel_dirty_page() changes. Signed-off-by: NSha Zhengju <handai.szj@gmail.com> Signed-off-by: NGreg Thelen <gthelen@google.com> Signed-off-by: NTejun Heo <tj@kernel.org> Signed-off-by: NJens Axboe <axboe@fb.com>
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- 16 4月, 2015 1 次提交
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由 Jason Low 提交于
We converted some of the usages of ACCESS_ONCE to READ_ONCE in the mm/ tree since it doesn't work reliably on non-scalar types. This patch removes the rest of the usages of ACCESS_ONCE, and use the new READ_ONCE API for the read accesses. This makes things cleaner, instead of using separate/multiple sets of APIs. Signed-off-by: NJason Low <jason.low2@hp.com> Acked-by: NMichal Hocko <mhocko@suse.cz> Acked-by: NDavidlohr Bueso <dave@stgolabs.net> Acked-by: NRik van Riel <riel@redhat.com> Reviewed-by: NChristian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 26 3月, 2015 1 次提交
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由 Leon Yu 提交于
I have constantly stumbled upon "kernel BUG at mm/rmap.c:399!" after upgrading to 3.19 and had no luck with 4.0-rc1 neither. So, after looking into new logic introduced by commit 7a3ef208 ("mm: prevent endless growth of anon_vma hierarchy"), I found chances are that unlink_anon_vmas() is called without incrementing dst->anon_vma->degree in anon_vma_clone() due to allocation failure. If dst->anon_vma is not NULL in error path, its degree will be incorrectly decremented in unlink_anon_vmas() and eventually underflow when exiting as a result of another call to unlink_anon_vmas(). That's how "kernel BUG at mm/rmap.c:399!" is triggered for me. This patch fixes the underflow by dropping dst->anon_vma when allocation fails. It's safe to do so regardless of original value of dst->anon_vma because dst->anon_vma doesn't have valid meaning if anon_vma_clone() fails. Besides, callers don't care dst->anon_vma in such case neither. Also suggested by Michal Hocko, we can clean up vma_adjust() a bit as anon_vma_clone() now does the work. [akpm@linux-foundation.org: tweak comment] Fixes: 7a3ef208 ("mm: prevent endless growth of anon_vma hierarchy") Signed-off-by: NLeon Yu <chianglungyu@gmail.com> Signed-off-by: NKonstantin Khlebnikov <koct9i@gmail.com> Reviewed-by: NMichal Hocko <mhocko@suse.cz> Acked-by: NRik van Riel <riel@redhat.com> Acked-by: NDavid Rientjes <rientjes@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 12 2月, 2015 1 次提交
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由 Johannes Weiner 提交于
The complexity of memcg page stat synchronization is currently leaking into the callsites, forcing them to keep track of the move_lock state and the IRQ flags. Simplify the API by tracking it in the memcg. Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org> Acked-by: NMichal Hocko <mhocko@suse.cz> Reviewed-by: NVladimir Davydov <vdavydov@parallels.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 11 2月, 2015 1 次提交
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由 Kirill A. Shutemov 提交于
We don't create non-linear mappings anymore. Let's drop code which handles them in rmap. Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 09 1月, 2015 1 次提交
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由 Konstantin Khlebnikov 提交于
Constantly forking task causes unlimited grow of anon_vma chain. Each next child allocates new level of anon_vmas and links vma to all previous levels because pages might be inherited from any level. This patch adds heuristic which decides to reuse existing anon_vma instead of forking new one. It adds counter anon_vma->degree which counts linked vmas and directly descending anon_vmas and reuses anon_vma if counter is lower than two. As a result each anon_vma has either vma or at least two descending anon_vmas. In such trees half of nodes are leafs with alive vmas, thus count of anon_vmas is no more than two times bigger than count of vmas. This heuristic reuses anon_vmas as few as possible because each reuse adds false aliasing among vmas and rmap walker ought to scan more ptes when it searches where page is might be mapped. Link: http://lkml.kernel.org/r/20120816024610.GA5350@evergreen.ssec.wisc.edu Fixes: 5beb4930 ("mm: change anon_vma linking to fix multi-process server scalability issue") [akpm@linux-foundation.org: fix typo, per Rik] Signed-off-by: NKonstantin Khlebnikov <koct9i@gmail.com> Reported-by: NDaniel Forrest <dan.forrest@ssec.wisc.edu> Tested-by: NMichal Hocko <mhocko@suse.cz> Tested-by: NJerome Marchand <jmarchan@redhat.com> Reviewed-by: NMichal Hocko <mhocko@suse.cz> Reviewed-by: NRik van Riel <riel@redhat.com> Cc: <stable@vger.kernel.org> [2.6.34+] Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 18 12月, 2014 1 次提交
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由 Christian Borntraeger 提交于
ACCESS_ONCE does not work reliably on non-scalar types. For example gcc 4.6 and 4.7 might remove the volatile tag for such accesses during the SRA (scalar replacement of aggregates) step (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145) Let's change the code to access the page table elements with READ_ONCE that does implicit scalar accesses for the gup code. mm_find_pmd is tricky, because m68k and sparc(32bit) define pmd_t as array of longs. This code requires just that the pmd_present and pmd_trans_huge check are done on the same value, so a barrier is sufficent. A similar case is in handle_pte_fault. On ppc44x the word size is 32 bit, but a pte is 64 bit. A barrier is ok as well. Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com> Cc: linux-mm@kvack.org Acked-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 14 12月, 2014 4 次提交
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由 Davidlohr Bueso 提交于
Call page_to_pgoff() to get the page offset once we are sure we actually need it, and any very obvious initial function checks have passed. Trivial micro-optimization, and potentially save some cycles. Signed-off-by: NDavidlohr Bueso <dbueso@suse.de> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Davidlohr Bueso 提交于
Similarly to the anon memory counterpart, we can share the mapping's lock ownership as the interval tree is not modified when doing doing the walk, only the file page. Signed-off-by: NDavidlohr Bueso <dbueso@suse.de> Acked-by: NRik van Riel <riel@redhat.com> Acked-by: N"Kirill A. Shutemov" <kirill@shutemov.name> Acked-by: NHugh Dickins <hughd@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: NMel Gorman <mgorman@suse.de> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Davidlohr Bueso 提交于
The i_mmap_mutex is a close cousin of the anon vma lock, both protecting similar data, one for file backed pages and the other for anon memory. To this end, this lock can also be a rwsem. In addition, there are some important opportunities to share the lock when there are no tree modifications. This conversion is straightforward. For now, all users take the write lock. [sfr@canb.auug.org.au: update fremap.c] Signed-off-by: NDavidlohr Bueso <dbueso@suse.de> Reviewed-by: NRik van Riel <riel@redhat.com> Acked-by: N"Kirill A. Shutemov" <kirill@shutemov.name> Acked-by: NHugh Dickins <hughd@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: NMel Gorman <mgorman@suse.de> Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Davidlohr Bueso 提交于
Convert all open coded mutex_lock/unlock calls to the i_mmap_[lock/unlock]_write() helpers. Signed-off-by: NDavidlohr Bueso <dbueso@suse.de> Acked-by: NRik van Riel <riel@redhat.com> Acked-by: N"Kirill A. Shutemov" <kirill@shutemov.name> Acked-by: NHugh Dickins <hughd@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: NMel Gorman <mgorman@suse.de> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 11 12月, 2014 1 次提交
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由 Michal Hocko 提交于
Since commit d7365e78 ("mm: memcontrol: fix missed end-writeback page accounting") mem_cgroup_end_page_stat consumes locked and flags variables directly rather than via pointers which might trigger C undefined behavior as those variables are initialized only in the slow path of mem_cgroup_begin_page_stat. Although mem_cgroup_end_page_stat handles parameters correctly and touches them only when they hold a sensible value it is caller which loads a potentially uninitialized value which then might allow compiler to do crazy things. I haven't seen any warning from gcc and it seems that the current version (4.9) doesn't exploit this type undefined behavior but Sasha has reported the following: UBSan: Undefined behaviour in mm/rmap.c:1084:2 load of value 255 is not a valid value for type '_Bool' CPU: 4 PID: 8304 Comm: rngd Not tainted 3.18.0-rc2-next-20141029-sasha-00039-g77ed13d-dirty #1427 Call Trace: dump_stack (lib/dump_stack.c:52) ubsan_epilogue (lib/ubsan.c:159) __ubsan_handle_load_invalid_value (lib/ubsan.c:482) page_remove_rmap (mm/rmap.c:1084 mm/rmap.c:1096) unmap_page_range (./arch/x86/include/asm/atomic.h:27 include/linux/mm.h:463 mm/memory.c:1146 mm/memory.c:1258 mm/memory.c:1279 mm/memory.c:1303) unmap_single_vma (mm/memory.c:1348) unmap_vmas (mm/memory.c:1377 (discriminator 3)) exit_mmap (mm/mmap.c:2837) mmput (kernel/fork.c:659) do_exit (./arch/x86/include/asm/thread_info.h:168 kernel/exit.c:462 kernel/exit.c:747) do_group_exit (include/linux/sched.h:775 kernel/exit.c:873) SyS_exit_group (kernel/exit.c:901) tracesys_phase2 (arch/x86/kernel/entry_64.S:529) Fix this by using pointer parameters for both locked and flags and be more robust for future compiler changes even though the current code is implemented correctly. Signed-off-by: NMichal Hocko <mhocko@suse.cz> Reported-by: NSasha Levin <sasha.levin@oracle.com> Acked-by: NJohannes Weiner <hannes@cmpxchg.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 04 12月, 2014 1 次提交
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由 Daniel Forrest 提交于
Andrew Morton noticed that the error return from anon_vma_clone() was being dropped and replaced with -ENOMEM (which is not itself a bug because the only error return value from anon_vma_clone() is -ENOMEM). I did an audit of callers of anon_vma_clone() and discovered an actual bug where the error return was being lost. In __split_vma(), between Linux 3.11 and 3.12 the code was changed so the err variable is used before the call to anon_vma_clone() and the default initial value of -ENOMEM is overwritten. So a failure of anon_vma_clone() will return success since err at this point is now zero. Below is a patch which fixes this bug and also propagates the error return value from anon_vma_clone() in all cases. Fixes: ef0855d3 ("mm: mempolicy: turn vma_set_policy() into vma_dup_policy()") Signed-off-by: NDaniel Forrest <dan.forrest@ssec.wisc.edu> Reviewed-by: NMichal Hocko <mhocko@suse.cz> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Tim Hartrick <tim@edgecast.com> Cc: Hugh Dickins <hughd@google.com> Cc: Michel Lespinasse <walken@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: <stable@vger.kernel.org> [3.12+] Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 30 10月, 2014 2 次提交
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由 Johannes Weiner 提交于
page_remove_rmap() has too many branches on PageAnon() and is hard to follow. Move the file part into a separate function. Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org> Reviewed-by: NMichal Hocko <mhocko@suse.cz> Cc: Vladimir Davydov <vdavydov@parallels.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Johannes Weiner 提交于
Commit 0a31bc97 ("mm: memcontrol: rewrite uncharge API") changed page migration to uncharge the old page right away. The page is locked, unmapped, truncated, and off the LRU, but it could race with writeback ending, which then doesn't unaccount the page properly: test_clear_page_writeback() migration wait_on_page_writeback() TestClearPageWriteback() mem_cgroup_migrate() clear PCG_USED mem_cgroup_update_page_stat() if (PageCgroupUsed(pc)) decrease memcg pages under writeback release pc->mem_cgroup->move_lock The per-page statistics interface is heavily optimized to avoid a function call and a lookup_page_cgroup() in the file unmap fast path, which means it doesn't verify whether a page is still charged before clearing PageWriteback() and it has to do it in the stat update later. Rework it so that it looks up the page's memcg once at the beginning of the transaction and then uses it throughout. The charge will be verified before clearing PageWriteback() and migration can't uncharge the page as long as that is still set. The RCU lock will protect the memcg past uncharge. As far as losing the optimization goes, the following test results are from a microbenchmark that maps, faults, and unmaps a 4GB sparse file three times in a nested fashion, so that there are two negative passes that don't account but still go through the new transaction overhead. There is no actual difference: old: 33.195102545 seconds time elapsed ( +- 0.01% ) new: 33.199231369 seconds time elapsed ( +- 0.03% ) The time spent in page_remove_rmap()'s callees still adds up to the same, but the time spent in the function itself seems reduced: # Children Self Command Shared Object Symbol old: 0.12% 0.11% filemapstress [kernel.kallsyms] [k] page_remove_rmap new: 0.12% 0.08% filemapstress [kernel.kallsyms] [k] page_remove_rmap Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org> Acked-by: NMichal Hocko <mhocko@suse.cz> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: <stable@vger.kernel.org> [3.17.x] Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 10 10月, 2014 1 次提交
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由 Sasha Levin 提交于
Trivially convert a few VM_BUG_ON calls to VM_BUG_ON_VMA to extract more information when they trigger. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: NSasha Levin <sasha.levin@oracle.com> Reviewed-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Konstantin Khlebnikov <khlebnikov@openvz.org> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Michal Hocko <mhocko@suse.cz> Cc: Hugh Dickins <hughd@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Michel Lespinasse <walken@google.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 24 9月, 2014 1 次提交
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由 Andres Lagar-Cavilla 提交于
1. We were calling clear_flush_young_notify in unmap_one, but we are within an mmu notifier invalidate range scope. The spte exists no more (due to range_start) and the accessed bit info has already been propagated (due to kvm_pfn_set_accessed). Simply call clear_flush_young. 2. We clear_flush_young on a primary MMU PMD, but this may be mapped as a collection of PTEs by the secondary MMU (e.g. during log-dirty). This required expanding the interface of the clear_flush_young mmu notifier, so a lot of code has been trivially touched. 3. In the absence of shadow_accessed_mask (e.g. EPT A bit), we emulate the access bit by blowing the spte. This requires proper synchronizing with MMU notifier consumers, like every other removal of spte's does. Signed-off-by: NAndres Lagar-Cavilla <andreslc@google.com> Acked-by: NRik van Riel <riel@redhat.com> Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
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- 09 8月, 2014 2 次提交
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由 Johannes Weiner 提交于
The memcg uncharging code that is involved towards the end of a page's lifetime - truncation, reclaim, swapout, migration - is impressively complicated and fragile. Because anonymous and file pages were always charged before they had their page->mapping established, uncharges had to happen when the page type could still be known from the context; as in unmap for anonymous, page cache removal for file and shmem pages, and swap cache truncation for swap pages. However, these operations happen well before the page is actually freed, and so a lot of synchronization is necessary: - Charging, uncharging, page migration, and charge migration all need to take a per-page bit spinlock as they could race with uncharging. - Swap cache truncation happens during both swap-in and swap-out, and possibly repeatedly before the page is actually freed. This means that the memcg swapout code is called from many contexts that make no sense and it has to figure out the direction from page state to make sure memory and memory+swap are always correctly charged. - On page migration, the old page might be unmapped but then reused, so memcg code has to prevent untimely uncharging in that case. Because this code - which should be a simple charge transfer - is so special-cased, it is not reusable for replace_page_cache(). But now that charged pages always have a page->mapping, introduce mem_cgroup_uncharge(), which is called after the final put_page(), when we know for sure that nobody is looking at the page anymore. For page migration, introduce mem_cgroup_migrate(), which is called after the migration is successful and the new page is fully rmapped. Because the old page is no longer uncharged after migration, prevent double charges by decoupling the page's memcg association (PCG_USED and pc->mem_cgroup) from the page holding an actual charge. The new bits PCG_MEM and PCG_MEMSW represent the respective charges and are transferred to the new page during migration. mem_cgroup_migrate() is suitable for replace_page_cache() as well, which gets rid of mem_cgroup_replace_page_cache(). However, care needs to be taken because both the source and the target page can already be charged and on the LRU when fuse is splicing: grab the page lock on the charge moving side to prevent changing pc->mem_cgroup of a page under migration. Also, the lruvecs of both pages change as we uncharge the old and charge the new during migration, and putback may race with us, so grab the lru lock and isolate the pages iff on LRU to prevent races and ensure the pages are on the right lruvec afterward. Swap accounting is massively simplified: because the page is no longer uncharged as early as swap cache deletion, a new mem_cgroup_swapout() can transfer the page's memory+swap charge (PCG_MEMSW) to the swap entry before the final put_page() in page reclaim. Finally, page_cgroup changes are now protected by whatever protection the page itself offers: anonymous pages are charged under the page table lock, whereas page cache insertions, swapin, and migration hold the page lock. Uncharging happens under full exclusion with no outstanding references. Charging and uncharging also ensure that the page is off-LRU, which serializes against charge migration. Remove the very costly page_cgroup lock and set pc->flags non-atomically. [mhocko@suse.cz: mem_cgroup_charge_statistics needs preempt_disable] [vdavydov@parallels.com: fix flags definition] Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org> Cc: Hugh Dickins <hughd@google.com> Cc: Tejun Heo <tj@kernel.org> Cc: Vladimir Davydov <vdavydov@parallels.com> Tested-by: NJet Chen <jet.chen@intel.com> Acked-by: NMichal Hocko <mhocko@suse.cz> Tested-by: NFelipe Balbi <balbi@ti.com> Signed-off-by: NVladimir Davydov <vdavydov@parallels.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Johannes Weiner 提交于
These patches rework memcg charge lifetime to integrate more naturally with the lifetime of user pages. This drastically simplifies the code and reduces charging and uncharging overhead. The most expensive part of charging and uncharging is the page_cgroup bit spinlock, which is removed entirely after this series. Here are the top-10 profile entries of a stress test that reads a 128G sparse file on a freshly booted box, without even a dedicated cgroup (i.e. executing in the root memcg). Before: 15.36% cat [kernel.kallsyms] [k] copy_user_generic_string 13.31% cat [kernel.kallsyms] [k] memset 11.48% cat [kernel.kallsyms] [k] do_mpage_readpage 4.23% cat [kernel.kallsyms] [k] get_page_from_freelist 2.38% cat [kernel.kallsyms] [k] put_page 2.32% cat [kernel.kallsyms] [k] __mem_cgroup_commit_charge 2.18% kswapd0 [kernel.kallsyms] [k] __mem_cgroup_uncharge_common 1.92% kswapd0 [kernel.kallsyms] [k] shrink_page_list 1.86% cat [kernel.kallsyms] [k] __radix_tree_lookup 1.62% cat [kernel.kallsyms] [k] __pagevec_lru_add_fn After: 15.67% cat [kernel.kallsyms] [k] copy_user_generic_string 13.48% cat [kernel.kallsyms] [k] memset 11.42% cat [kernel.kallsyms] [k] do_mpage_readpage 3.98% cat [kernel.kallsyms] [k] get_page_from_freelist 2.46% cat [kernel.kallsyms] [k] put_page 2.13% kswapd0 [kernel.kallsyms] [k] shrink_page_list 1.88% cat [kernel.kallsyms] [k] __radix_tree_lookup 1.67% cat [kernel.kallsyms] [k] __pagevec_lru_add_fn 1.39% kswapd0 [kernel.kallsyms] [k] free_pcppages_bulk 1.30% cat [kernel.kallsyms] [k] kfree As you can see, the memcg footprint has shrunk quite a bit. text data bss dec hex filename 37970 9892 400 48262 bc86 mm/memcontrol.o.old 35239 9892 400 45531 b1db mm/memcontrol.o This patch (of 4): The memcg charge API charges pages before they are rmapped - i.e. have an actual "type" - and so every callsite needs its own set of charge and uncharge functions to know what type is being operated on. Worse, uncharge has to happen from a context that is still type-specific, rather than at the end of the page's lifetime with exclusive access, and so requires a lot of synchronization. Rewrite the charge API to provide a generic set of try_charge(), commit_charge() and cancel_charge() transaction operations, much like what's currently done for swap-in: mem_cgroup_try_charge() attempts to reserve a charge, reclaiming pages from the memcg if necessary. mem_cgroup_commit_charge() commits the page to the charge once it has a valid page->mapping and PageAnon() reliably tells the type. mem_cgroup_cancel_charge() aborts the transaction. This reduces the charge API and enables subsequent patches to drastically simplify uncharging. As pages need to be committed after rmap is established but before they are added to the LRU, page_add_new_anon_rmap() must stop doing LRU additions again. Revive lru_cache_add_active_or_unevictable(). [hughd@google.com: fix shmem_unuse] [hughd@google.com: Add comments on the private use of -EAGAIN] Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org> Acked-by: NMichal Hocko <mhocko@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Vladimir Davydov <vdavydov@parallels.com> Signed-off-by: NHugh Dickins <hughd@google.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 24 7月, 2014 1 次提交
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由 Naoya Horiguchi 提交于
I triggered VM_BUG_ON() in vma_address() when I tried to migrate an anonymous hugepage with mbind() in the kernel v3.16-rc3. This is because pgoff's calculation in rmap_walk_anon() fails to consider compound_order() only to have an incorrect value. This patch introduces page_to_pgoff(), which gets the page's offset in PAGE_CACHE_SIZE. Kirill pointed out that page cache tree should natively handle hugepages, and in order to make hugetlbfs fit it, page->index of hugetlbfs page should be in PAGE_CACHE_SIZE. This is beyond this patch, but page_to_pgoff() contains the point to be fixed in a single function. Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com> Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Hugh Dickins <hughd@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Hillf Danton <dhillf@gmail.com> Cc: Naoya Horiguchi <nao.horiguchi@gmail.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 24 6月, 2014 1 次提交
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由 Hugh Dickins 提交于
Trinity has reported: BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 IP: __lock_acquire (kernel/locking/lockdep.c:3070 (discriminator 1)) CPU: 6 PID: 16173 Comm: trinity-c364 Tainted: G W 3.15.0-rc1-next-20140415-sasha-00020-gaa90d09 #398 lock_acquire (arch/x86/include/asm/current.h:14 kernel/locking/lockdep.c:3602) _raw_spin_lock (include/linux/spinlock_api_smp.h:143 kernel/locking/spinlock.c:151) remove_migration_pte (mm/migrate.c:137) rmap_walk (mm/rmap.c:1628 mm/rmap.c:1699) remove_migration_ptes (mm/migrate.c:224) migrate_pages (mm/migrate.c:922 mm/migrate.c:960 mm/migrate.c:1126) migrate_misplaced_page (mm/migrate.c:1733) __handle_mm_fault (mm/memory.c:3762 mm/memory.c:3812 mm/memory.c:3925) handle_mm_fault (mm/memory.c:3948) __get_user_pages (mm/memory.c:1851) __mlock_vma_pages_range (mm/mlock.c:255) __mm_populate (mm/mlock.c:711) SyS_mlockall (include/linux/mm.h:1799 mm/mlock.c:817 mm/mlock.c:791) I believe this comes about because, whereas collapsing and splitting THP functions take anon_vma lock in write mode (which excludes concurrent rmap walks), faulting THP functions (write protection and misplaced NUMA) do not - and mostly they do not need to. But they do use a pmdp_clear_flush(), set_pmd_at() sequence which, for an instant (indeed, for a long instant, given the inter-CPU TLB flush in there), leaves *pmd neither present not trans_huge. Which can confuse a concurrent rmap walk, as when removing migration ptes, seen in the dumped trace. Although that rmap walk has a 4k page to insert, anon_vmas containing THPs are in no way segregated from 4k-page anon_vmas, so the 4k-intent mm_find_pmd() does need to cope with that instant when a trans_huge pmd is temporarily absent. I don't think we need strengthen the locking at the THP end: it's easily handled with an ACCESS_ONCE() before testing both conditions. And since mm_find_pmd() had only one caller who wanted a THP rather than a pmd, let's slightly repurpose it to fail when it hits a THP or non-present pmd, and open code split_huge_page_address() again. Signed-off-by: NHugh Dickins <hughd@google.com> Reported-by: NSasha Levin <sasha.levin@oracle.com> Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Bob Liu <bob.liu@oracle.com> Cc: Christoph Lameter <cl@gentwo.org> Cc: Dave Jones <davej@redhat.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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