- 14 1月, 2011 3 次提交
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由 Andrea Arcangeli 提交于
This documents how split_huge_page is safe vs new vma inserctions into the anon_vma that may have already released the anon_vma->lock but not established pmds yet when split_huge_page starts. Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com> Acked-by: NMel Gorman <mel@csn.ul.ie> 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
Lately I've been working to make KVM use hugepages transparently without the usual restrictions of hugetlbfs. Some of the restrictions I'd like to see removed: 1) hugepages have to be swappable or the guest physical memory remains locked in RAM and can't be paged out to swap 2) if a hugepage allocation fails, regular pages should be allocated instead and mixed in the same vma without any failure and without userland noticing 3) if some task quits and more hugepages become available in the buddy, guest physical memory backed by regular pages should be relocated on hugepages automatically in regions under madvise(MADV_HUGEPAGE) (ideally event driven by waking up the kernel deamon if the order=HPAGE_PMD_SHIFT-PAGE_SHIFT list becomes not null) 4) avoidance of reservation and maximization of use of hugepages whenever possible. Reservation (needed to avoid runtime fatal faliures) may be ok for 1 machine with 1 database with 1 database cache with 1 database cache size known at boot time. It's definitely not feasible with a virtualization hypervisor usage like RHEV-H that runs an unknown number of virtual machines with an unknown size of each virtual machine with an unknown amount of pagecache that could be potentially useful in the host for guest not using O_DIRECT (aka cache=off). hugepages in the virtualization hypervisor (and also in the guest!) are much more important than in a regular host not using virtualization, becasue with NPT/EPT they decrease the tlb-miss cacheline accesses from 24 to 19 in case only the hypervisor uses transparent hugepages, and they decrease the tlb-miss cacheline accesses from 19 to 15 in case both the linux hypervisor and the linux guest both uses this patch (though the guest will limit the addition speedup to anonymous regions only for now...). Even more important is that the tlb miss handler is much slower on a NPT/EPT guest than for a regular shadow paging or no-virtualization scenario. So maximizing the amount of virtual memory cached by the TLB pays off significantly more with NPT/EPT than without (even if there would be no significant speedup in the tlb-miss runtime). The first (and more tedious) part of this work requires allowing the VM to handle anonymous hugepages mixed with regular pages transparently on regular anonymous vmas. This is what this patch tries to achieve in the least intrusive possible way. We want hugepages and hugetlb to be used in a way so that all applications can benefit without changes (as usual we leverage the KVM virtualization design: by improving the Linux VM at large, KVM gets the performance boost too). The most important design choice is: always fallback to 4k allocation if the hugepage allocation fails! This is the _very_ opposite of some large pagecache patches that failed with -EIO back then if a 64k (or similar) allocation failed... Second important decision (to reduce the impact of the feature on the existing pagetable handling code) is that at any time we can split an hugepage into 512 regular pages and it has to be done with an operation that can't fail. This way the reliability of the swapping isn't decreased (no need to allocate memory when we are short on memory to swap) and it's trivial to plug a split_huge_page* one-liner where needed without polluting the VM. Over time we can teach mprotect, mremap and friends to handle pmd_trans_huge natively without calling split_huge_page*. The fact it can't fail isn't just for swap: if split_huge_page would return -ENOMEM (instead of the current void) we'd need to rollback the mprotect from the middle of it (ideally including undoing the split_vma) which would be a big change and in the very wrong direction (it'd likely be simpler not to call split_huge_page at all and to teach mprotect and friends to handle hugepages instead of rolling them back from the middle). In short the very value of split_huge_page is that it can't fail. The collapsing and madvise(MADV_HUGEPAGE) part will remain separated and incremental and it'll just be an "harmless" addition later if this initial part is agreed upon. It also should be noted that locking-wise replacing regular pages with hugepages is going to be very easy if compared to what I'm doing below in split_huge_page, as it will only happen when page_count(page) matches page_mapcount(page) if we can take the PG_lock and mmap_sem in write mode. collapse_huge_page will be a "best effort" that (unlike split_huge_page) can fail at the minimal sign of trouble and we can try again later. collapse_huge_page will be similar to how KSM works and the madvise(MADV_HUGEPAGE) will work similar to madvise(MADV_MERGEABLE). The default I like is that transparent hugepages are used at page fault time. This can be changed with /sys/kernel/mm/transparent_hugepage/enabled. The control knob can be set to three values "always", "madvise", "never" which mean respectively that hugepages are always used, or only inside madvise(MADV_HUGEPAGE) regions, or never used. /sys/kernel/mm/transparent_hugepage/defrag instead controls if the hugepage allocation should defrag memory aggressively "always", only inside "madvise" regions, or "never". The pmd_trans_splitting/pmd_trans_huge locking is very solid. The put_page (from get_user_page users that can't use mmu notifier like O_DIRECT) that runs against a __split_huge_page_refcount instead was a pain to serialize in a way that would result always in a coherent page count for both tail and head. I think my locking solution with a compound_lock taken only after the page_first is valid and is still a PageHead should be safe but it surely needs review from SMP race point of view. In short there is no current existing way to serialize the O_DIRECT final put_page against split_huge_page_refcount so I had to invent a new one (O_DIRECT loses knowledge on the mapping status by the time gup_fast returns so...). And I didn't want to impact all gup/gup_fast users for now, maybe if we change the gup interface substantially we can avoid this locking, I admit I didn't think too much about it because changing the gup unpinning interface would be invasive. If we ignored O_DIRECT we could stick to the existing compound refcounting code, by simply adding a get_user_pages_fast_flags(foll_flags) where KVM (and any other mmu notifier user) would call it without FOLL_GET (and if FOLL_GET isn't set we'd just BUG_ON if nobody registered itself in the current task mmu notifier list yet). But O_DIRECT is fundamental for decent performance of virtualized I/O on fast storage so we can't avoid it to solve the race of put_page against split_huge_page_refcount to achieve a complete hugepage feature for KVM. Swap and oom works fine (well just like with regular pages ;). MMU notifier is handled transparently too, with the exception of the young bit on the pmd, that didn't have a range check but I think KVM will be fine because the whole point of hugepages is that EPT/NPT will also use a huge pmd when they notice gup returns pages with PageCompound set, so they won't care of a range and there's just the pmd young bit to check in that case. NOTE: in some cases if the L2 cache is small, this may slowdown and waste memory during COWs because 4M of memory are accessed in a single fault instead of 8k (the payoff is that after COW the program can run faster). So we might want to switch the copy_huge_page (and clear_huge_page too) to not temporal stores. I also extensively researched ways to avoid this cache trashing with a full prefault logic that would cow in 8k/16k/32k/64k up to 1M (I can send those patches that fully implemented prefault) but I concluded they're not worth it and they add an huge additional complexity and they remove all tlb benefits until the full hugepage has been faulted in, to save a little bit of memory and some cache during app startup, but they still don't improve substantially the cache-trashing during startup if the prefault happens in >4k chunks. One reason is that those 4k pte entries copied are still mapped on a perfectly cache-colored hugepage, so the trashing is the worst one can generate in those copies (cow of 4k page copies aren't so well colored so they trashes less, but again this results in software running faster after the page fault). Those prefault patches allowed things like a pte where post-cow pages were local 4k regular anon pages and the not-yet-cowed pte entries were pointing in the middle of some hugepage mapped read-only. If it doesn't payoff substantially with todays hardware it will payoff even less in the future with larger l2 caches, and the prefault logic would blot the VM a lot. If one is emebdded transparent_hugepage can be disabled during boot with sysfs or with the boot commandline parameter transparent_hugepage=0 (or transparent_hugepage=2 to restrict hugepages inside madvise regions) that will ensure not a single hugepage is allocated at boot time. It is simple enough to just disable transparent hugepage globally and let transparent hugepages be allocated selectively by applications in the MADV_HUGEPAGE region (both at page fault time, and if enabled with the collapse_huge_page too through the kernel daemon). This patch supports only hugepages mapped in the pmd, archs that have smaller hugepages will not fit in this patch alone. Also some archs like power have certain tlb limits that prevents mixing different page size in the same regions so they will not fit in this framework that requires "graceful fallback" to basic PAGE_SIZE in case of physical memory fragmentation. hugetlbfs remains a perfect fit for those because its software limits happen to match the hardware limits. hugetlbfs also remains a perfect fit for hugepage sizes like 1GByte that cannot be hoped to be found not fragmented after a certain system uptime and that would be very expensive to defragment with relocation, so requiring reservation. hugetlbfs is the "reservation way", the point of transparent hugepages is not to have any reservation at all and maximizing the use of cache and hugepages at all times automatically. Some performance result: vmx andrea # LD_PRELOAD=/usr/lib64/libhugetlbfs.so HUGETLB_MORECORE=yes HUGETLB_PATH=/mnt/huge/ ./largep ages3 memset page fault 1566023 memset tlb miss 453854 memset second tlb miss 453321 random access tlb miss 41635 random access second tlb miss 41658 vmx andrea # LD_PRELOAD=/usr/lib64/libhugetlbfs.so HUGETLB_MORECORE=yes HUGETLB_PATH=/mnt/huge/ ./largepages3 memset page fault 1566471 memset tlb miss 453375 memset second tlb miss 453320 random access tlb miss 41636 random access second tlb miss 41637 vmx andrea # ./largepages3 memset page fault 1566642 memset tlb miss 453417 memset second tlb miss 453313 random access tlb miss 41630 random access second tlb miss 41647 vmx andrea # ./largepages3 memset page fault 1566872 memset tlb miss 453418 memset second tlb miss 453315 random access tlb miss 41618 random access second tlb miss 41659 vmx andrea # echo 0 > /proc/sys/vm/transparent_hugepage vmx andrea # ./largepages3 memset page fault 2182476 memset tlb miss 460305 memset second tlb miss 460179 random access tlb miss 44483 random access second tlb miss 44186 vmx andrea # ./largepages3 memset page fault 2182791 memset tlb miss 460742 memset second tlb miss 459962 random access tlb miss 43981 random access second tlb miss 43988 ============ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/time.h> #define SIZE (3UL*1024*1024*1024) int main() { char *p = malloc(SIZE), *p2; struct timeval before, after; gettimeofday(&before, NULL); memset(p, 0, SIZE); gettimeofday(&after, NULL); printf("memset page fault %Lu\n", (after.tv_sec-before.tv_sec)*1000000UL + after.tv_usec-before.tv_usec); gettimeofday(&before, NULL); memset(p, 0, SIZE); gettimeofday(&after, NULL); printf("memset tlb miss %Lu\n", (after.tv_sec-before.tv_sec)*1000000UL + after.tv_usec-before.tv_usec); gettimeofday(&before, NULL); memset(p, 0, SIZE); gettimeofday(&after, NULL); printf("memset second tlb miss %Lu\n", (after.tv_sec-before.tv_sec)*1000000UL + after.tv_usec-before.tv_usec); gettimeofday(&before, NULL); for (p2 = p; p2 < p+SIZE; p2 += 4096) *p2 = 0; gettimeofday(&after, NULL); printf("random access tlb miss %Lu\n", (after.tv_sec-before.tv_sec)*1000000UL + after.tv_usec-before.tv_usec); gettimeofday(&before, NULL); for (p2 = p; p2 < p+SIZE; p2 += 4096) *p2 = 0; gettimeofday(&after, NULL); printf("random access second tlb miss %Lu\n", (after.tv_sec-before.tv_sec)*1000000UL + after.tv_usec-before.tv_usec); return 0; } ============ Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com> Acked-by: NRik van Riel <riel@redhat.com> Signed-off-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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由 Andrea Arcangeli 提交于
Paging logic that splits the page before it is unmapped and added to swap to ensure backwards compatibility with the legacy swap code. Eventually swap should natively pageout the hugepages to increase performance and decrease seeking and fragmentation of swap space. swapoff can just skip over huge pmd as they cannot be part of swap yet. In add_to_swap be careful to split the page only if we got a valid swap entry so we don't split hugepages with a full swap. In theory we could split pages before isolating them during the lru scan, but for khugepaged to be safe, I'm relying on either mmap_sem write mode, or PG_lock taken, so split_huge_page has to run either with mmap_sem read/write mode or PG_lock taken. Calling it from isolate_lru_page would make locking more complicated, in addition to that split_huge_page would deadlock if called by __isolate_lru_page because it has to take the lru lock to add the tail pages. Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com> Acked-by: NMel Gorman <mel@csn.ul.ie> Acked-by: NRik van Riel <riel@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 27 12月, 2010 1 次提交
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由 Figo.zhang 提交于
clean up comment. Signed-off-by: NFigo.zhang <figo1802@gmail.com> Acked-by: NRik van Riel <riel@redhat.com> Signed-off-by: NJiri Kosina <jkosina@suse.cz>
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- 27 10月, 2010 3 次提交
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由 Namhyung Kim 提交于
Make anon_vma_chain_free() static. It is called only in rmap.c and the corresponding alloc function is already static. Signed-off-by: NNamhyung Kim <namhyung@gmail.com> Cc: Andi Kleen <andi@firstfloor.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Namhyung Kim 提交于
The page_check_address() conditionally grabs *@ptlp in case of returning non-NULL. Rename and wrap it using __cond_lock() removes following warnings from sparse: mm/rmap.c:472:9: warning: context imbalance in 'page_mapped_in_vma' - unexpected unlock mm/rmap.c:524:9: warning: context imbalance in 'page_referenced_one' - unexpected unlock mm/rmap.c:706:9: warning: context imbalance in 'page_mkclean_one' - unexpected unlock mm/rmap.c:1066:9: warning: context imbalance in 'try_to_unmap_one' - unexpected unlock Signed-off-by: NNamhyung Kim <namhyung@gmail.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Namhyung Kim 提交于
The page_lock_anon_vma() conditionally grabs RCU and anon_vma lock but page_unlock_anon_vma() releases them unconditionally. This leads sparse to complain about context imbalance. Annotate them. Signed-off-by: NNamhyung Kim <namhyung@gmail.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 25 10月, 2010 1 次提交
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由 Martin Schwidefsky 提交于
Improve performance of the sske operation by using the nonquiescing variant if the affected page has no mappings established. On machines with no support for the new sske variant the mask bit will be ignored. Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
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- 08 10月, 2010 1 次提交
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由 Andi Kleen 提交于
Linus asked for a cleanup of __page_set_anon_rmap to make it look more like the cleaner huge pages version. Factor out the duplicated PageAnon check into a single check at the beginning of the function. Remove obsolete comments and rewrite them into standard English. No functional changes. Signed-off-by: NAndi Kleen <ak@linux.intel.com>
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- 05 10月, 2010 1 次提交
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由 Hugh Dickins 提交于
2.6.36-rc1 commit 21d0d443 "rmap: resurrect page_address_in_vma anon_vma check" was right to resurrect that check; but now that it's comparing anon_vma->roots instead of just anon_vmas, there's a danger of oopsing on a NULL anon_vma. In most cases no NULL anon_vma ever gets here; but it turns out that occasionally KSM, when enabled on a forked or forking process, will itself call page_address_in_vma() on a "half-KSM" page left over from an earlier failed attempt to merge - whose page_anon_vma() is NULL. It's my bug that those should be getting here at all: I thought they were already dealt with, this oops proves me wrong, I'll fix it in the next release - such pages are effectively pinned until their process exits, since rmap cannot find their ptes (though swapoff can). For now just work around it by making page_address_in_vma() safe (and add a comment on why that check is wanted anyway). A similar check in __page_check_anon_rmap() is safe because do_page_add_anon_rmap() already excluded KSM pages. Signed-off-by: NHugh Dickins <hughd@google.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 24 9月, 2010 2 次提交
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由 Naoya Horiguchi 提交于
Confirming page lock is held in hugetlb_add_anon_rmap() may be useful to detect possible future problems. Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com> Acked-by: NRik van Riel <riel@redhat.com> Acked-by: NAndrea Arcangeli <aarcange@redhat.com> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Naoya Horiguchi 提交于
This patch applies Andrea's fix given by the following patch into hugepage rmapping code: commit 288468c3 Author: Andrea Arcangeli <aarcange@redhat.com> Date: Mon Aug 9 17:19:09 2010 -0700 This patch uses anon_vma->root and avoids unnecessary overwriting when anon_vma is already set up. Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com> Acked-by: NAndrea Arcangeli <aarcange@redhat.com> Reviewed-by: NRik van Riel <riel@redhat.com> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 29 8月, 2010 1 次提交
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由 Hugh Dickins 提交于
After several hours, kbuild tests hang with anon_vma_prepare() spinning on a newly allocated anon_vma's lock - on a box with CONFIG_TREE_PREEMPT_RCU=y (which makes this very much more likely, but it could happen without). The ever-subtle page_lock_anon_vma() now needs a further twist: since anon_vma_prepare() and anon_vma_fork() are liable to change the ->root of a reused anon_vma structure at any moment, page_lock_anon_vma() needs to check page_mapped() again before succeeding, otherwise page_unlock_anon_vma() might address a different root->lock. Signed-off-by: NHugh Dickins <hughd@google.com> Reviewed-by: NRik van Riel <riel@redhat.com> Cc: Christoph Lameter <cl@linux.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 11 8月, 2010 2 次提交
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由 Naoya Horiguchi 提交于
CONFIG_HUGETLBFS controls hugetlbfs interface code. OTOH, CONFIG_HUGETLB_PAGE controls hugepage management code. So we should use CONFIG_HUGETLB_PAGE here. Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: NAndi Kleen <ak@linux.intel.com>
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由 Naoya Horiguchi 提交于
This patch adds reverse mapping feature for hugepage by introducing mapcount for shared/private-mapped hugepage and anon_vma for private-mapped hugepage. While hugepage is not currently swappable, reverse mapping can be useful for memory error handler. Without this patch, memory error handler cannot identify processes using the bad hugepage nor unmap it from them. That is: - for shared hugepage: we can collect processes using a hugepage through pagecache, but can not unmap the hugepage because of the lack of mapcount. - for privately mapped hugepage: we can neither collect processes nor unmap the hugepage. This patch solves these problems. This patch include the bug fix given by commit 23be7468, so reverts it. Dependency: "hugetlb: move definition of is_vm_hugetlb_page() to hugepage_inline.h" ChangeLog since May 24. - create hugetlb_inline.h and move is_vm_hugetlb_index() in it. - move functions setting up anon_vma for hugepage into mm/rmap.c. ChangeLog since May 13. - rebased to 2.6.34 - fix logic error (in case that private mapping and shared mapping coexist) - move is_vm_hugetlb_page() into include/linux/mm.h to use this function from linear_page_index() - define and use linear_hugepage_index() instead of compound_order() - use page_move_anon_rmap() in hugetlb_cow() - copy exclusive switch of __set_page_anon_rmap() into hugepage counterpart. - revert commit 24be7468 completely Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Larry Woodman <lwoodman@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com> Acked-by: NFengguang Wu <fengguang.wu@intel.com> Acked-by: NMel Gorman <mel@csn.ul.ie> Signed-off-by: NAndi Kleen <ak@linux.intel.com>
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- 10 8月, 2010 8 次提交
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由 Rik van Riel 提交于
On swapin it is fairly common for a page to be owned exclusively by one process. In that case we want to add the page to the anon_vma of that process's VMA, instead of to the root anon_vma. This will reduce the amount of rmap searching that the swapout code needs to do. Signed-off-by: NRik van Riel <riel@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.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
Verify the refcounting doesn't go wrong, and resurrect the check in __page_check_anon_rmap as in old anon-vma code. Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com> Signed-off-by: NRik van Riel <riel@redhat.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
With root anon-vma it's trivial to keep doing the usual check as in old-anon-vma code. Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com> Signed-off-by: NRik van Riel <riel@redhat.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
Always use anon_vma->root pointer instead of anon_vma_chain.prev. Also optimize the map-paths, if a mapping is already established no need to overwrite it with root anon-vma list, we can keep the more finegrined anon-vma and skip the overwrite: see the PageAnon check in !exclusive case. This is also the optimization that hidden the ksm bug as this tends to make ksm_might_need_to_copy skip the copy, but only the proper fix to ksm_might_need_to_copy guarantees not triggering the ksm bug unless ksm is in use. this is an optimization only... [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com> Signed-off-by: NRik van Riel <riel@redhat.com> [kamezawa.hiroyu@jp.fujitsu.com: fix false positive BUG_ON in __page_set_anon_rmap] 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
Make sure to always add new VMAs at the end of the list. This is important so rmap_walk does not miss a VMA that was created during the rmap_walk. The old code got this right most of the time due to luck, but was buggy when anon_vma_prepare reused a mergeable anon_vma. Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com> Signed-off-by: NRik van Riel <riel@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Rik van Riel 提交于
KSM reference counts can cause an anon_vma to exist after the processe it belongs to have already exited. Because the anon_vma lock now lives in the root anon_vma, we need to ensure that the root anon_vma stays around until after all the "child" anon_vmas have been freed. The obvious way to do this is to have a "child" anon_vma take a reference to the root in anon_vma_fork. When the anon_vma is freed at munmap or process exit, we drop the refcount in anon_vma_unlink and possibly free the root anon_vma. The KSM anon_vma reference count function also needs to be modified to deal with the possibility of freeing 2 levels of anon_vma. The easiest way to do this is to break out the KSM magic and make it generic. When compiling without CONFIG_KSM, this code is compiled out. Signed-off-by: NRik van Riel <riel@redhat.com> Tested-by: NLarry Woodman <lwoodman@redhat.com> Acked-by: NLarry Woodman <lwoodman@redhat.com> Reviewed-by: NMinchan Kim <minchan.kim@gmail.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: NMel Gorman <mel@csn.ul.ie> Acked-by: NLinus Torvalds <torvalds@linux-foundation.org> Tested-by: NDave Young <hidave.darkstar@gmail.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Rik van Riel 提交于
Track the root (oldest) anon_vma in each anon_vma tree. Because we only take the lock on the root anon_vma, we cannot use the lock on higher-up anon_vmas to lock anything. This makes it impossible to do an indirect lookup of the root anon_vma, since the data structures could go away from under us. However, a direct pointer is safe because the root anon_vma is always the last one that gets freed on munmap or exit, by virtue of the same_vma list order and unlink_anon_vmas walking the list forward. [akpm@linux-foundation.org: fix typo] Signed-off-by: NRik van Riel <riel@redhat.com> Acked-by: NMel Gorman <mel@csn.ul.ie> Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Tested-by: NLarry Woodman <lwoodman@redhat.com> Acked-by: NLarry Woodman <lwoodman@redhat.com> Reviewed-by: NMinchan Kim <minchan.kim@gmail.com> Acked-by: NLinus 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 Rik van Riel 提交于
Subsitute a direct call of spin_lock(anon_vma->lock) with an inline function doing exactly the same. This makes it easier to do the substitution to the root anon_vma lock in a following patch. We will deal with the handful of special locks (nested, dec_and_lock, etc) separately. Signed-off-by: NRik van Riel <riel@redhat.com> Acked-by: NMel Gorman <mel@csn.ul.ie> Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Tested-by: NLarry Woodman <lwoodman@redhat.com> Acked-by: NLarry Woodman <lwoodman@redhat.com> Reviewed-by: NMinchan Kim <minchan.kim@gmail.com> Acked-by: NLinus 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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- 25 5月, 2010 3 次提交
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由 Mel Gorman 提交于
mm: migration: avoid race between shift_arg_pages() and rmap_walk() during migration by not migrating temporary stacks Page migration requires rmap to be able to find all ptes mapping a page at all times, otherwise the migration entry can be instantiated, but it is possible to leave one behind if the second rmap_walk fails to find the page. If this page is later faulted, migration_entry_to_page() will call BUG because the page is locked indicating the page was migrated by the migration PTE not cleaned up. For example kernel BUG at include/linux/swapops.h:105! invalid opcode: 0000 [#1] PREEMPT SMP ... Call Trace: [<ffffffff810e951a>] handle_mm_fault+0x3f8/0x76a [<ffffffff8130c7a2>] do_page_fault+0x44a/0x46e [<ffffffff813099b5>] page_fault+0x25/0x30 [<ffffffff8114de33>] load_elf_binary+0x152a/0x192b [<ffffffff8111329b>] search_binary_handler+0x173/0x313 [<ffffffff81114896>] do_execve+0x219/0x30a [<ffffffff8100a5c6>] sys_execve+0x43/0x5e [<ffffffff8100320a>] stub_execve+0x6a/0xc0 RIP [<ffffffff811094ff>] migration_entry_wait+0xc1/0x129 There is a race between shift_arg_pages and migration that triggers this bug. A temporary stack is setup during exec and later moved. If migration moves a page in the temporary stack and the VMA is then removed before migration completes, the migration PTE may not be found leading to a BUG when the stack is faulted. This patch causes pages within the temporary stack during exec to be skipped by migration. It does this by marking the VMA covering the temporary stack with an otherwise impossible combination of VMA flags. These flags are cleared when the temporary stack is moved to its final location. [kamezawa.hiroyu@jp.fujitsu.com: idea for having migration skip temporary stacks] Signed-off-by: NMel Gorman <mel@csn.ul.ie> Reviewed-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Reviewed-by: NRik van Riel <riel@redhat.com> Acked-by: NLinus Torvalds <torvalds@linux-foundation.org> Cc: Minchan Kim <minchan.kim@gmail.com> Cc: Christoph Lameter <cl@linux.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Reviewed-by: NKOSAKI 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 Mel Gorman 提交于
For clarity of review, KSM and page migration have separate refcounts on the anon_vma. While clear, this is a waste of memory. This patch gets KSM and page migration to share their toys in a spirit of harmony. Signed-off-by: NMel Gorman <mel@csn.ul.ie> Reviewed-by: NMinchan Kim <minchan.kim@gmail.com> Reviewed-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: NChristoph Lameter <cl@linux-foundation.org> Reviewed-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Rik van Riel <riel@redhat.com> 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
This patchset is a memory compaction mechanism that reduces external fragmentation memory by moving GFP_MOVABLE pages to a fewer number of pageblocks. The term "compaction" was chosen as there are is a number of mechanisms that are not mutually exclusive that can be used to defragment memory. For example, lumpy reclaim is a form of defragmentation as was slub "defragmentation" (really a form of targeted reclaim). Hence, this is called "compaction" to distinguish it from other forms of defragmentation. In this implementation, a full compaction run involves two scanners operating within a zone - a migration and a free scanner. The migration scanner starts at the beginning of a zone and finds all movable pages within one pageblock_nr_pages-sized area and isolates them on a migratepages list. The free scanner begins at the end of the zone and searches on a per-area basis for enough free pages to migrate all the pages on the migratepages list. As each area is respectively migrated or exhausted of free pages, the scanners are advanced one area. A compaction run completes within a zone when the two scanners meet. This method is a bit primitive but is easy to understand and greater sophistication would require maintenance of counters on a per-pageblock basis. This would have a big impact on allocator fast-paths to improve compaction which is a poor trade-off. It also does not try relocate virtually contiguous pages to be physically contiguous. However, assuming transparent hugepages were in use, a hypothetical khugepaged might reuse compaction code to isolate free pages, split them and relocate userspace pages for promotion. Memory compaction can be triggered in one of three ways. It may be triggered explicitly by writing any value to /proc/sys/vm/compact_memory and compacting all of memory. It can be triggered on a per-node basis by writing any value to /sys/devices/system/node/nodeN/compact where N is the node ID to be compacted. When a process fails to allocate a high-order page, it may compact memory in an attempt to satisfy the allocation instead of entering direct reclaim. Explicit compaction does not finish until the two scanners meet and direct compaction ends if a suitable page becomes available that would meet watermarks. The series is in 14 patches. The first three are not "core" to the series but are important pre-requisites. Patch 1 reference counts anon_vma for rmap_walk_anon(). Without this patch, it's possible to use anon_vma after free if the caller is not holding a VMA or mmap_sem for the pages in question. While there should be no existing user that causes this problem, it's a requirement for memory compaction to be stable. The patch is at the start of the series for bisection reasons. Patch 2 merges the KSM and migrate counts. It could be merged with patch 1 but would be slightly harder to review. Patch 3 skips over unmapped anon pages during migration as there are no guarantees about the anon_vma existing. There is a window between when a page was isolated and migration started during which anon_vma could disappear. Patch 4 notes that PageSwapCache pages can still be migrated even if they are unmapped. Patch 5 allows CONFIG_MIGRATION to be set without CONFIG_NUMA Patch 6 exports a "unusable free space index" via debugfs. It's a measure of external fragmentation that takes the size of the allocation request into account. It can also be calculated from userspace so can be dropped if requested Patch 7 exports a "fragmentation index" which only has meaning when an allocation request fails. It determines if an allocation failure would be due to a lack of memory or external fragmentation. Patch 8 moves the definition for LRU isolation modes for use by compaction Patch 9 is the compaction mechanism although it's unreachable at this point Patch 10 adds a means of compacting all of memory with a proc trgger Patch 11 adds a means of compacting a specific node with a sysfs trigger Patch 12 adds "direct compaction" before "direct reclaim" if it is determined there is a good chance of success. Patch 13 adds a sysctl that allows tuning of the threshold at which the kernel will compact or direct reclaim Patch 14 temporarily disables compaction if an allocation failure occurs after compaction. Testing of compaction was in three stages. For the test, debugging, preempt, the sleep watchdog and lockdep were all enabled but nothing nasty popped out. min_free_kbytes was tuned as recommended by hugeadm to help fragmentation avoidance and high-order allocations. It was tested on X86, X86-64 and PPC64. Ths first test represents one of the easiest cases that can be faced for lumpy reclaim or memory compaction. 1. Machine freshly booted and configured for hugepage usage with a) hugeadm --create-global-mounts b) hugeadm --pool-pages-max DEFAULT:8G c) hugeadm --set-recommended-min_free_kbytes d) hugeadm --set-recommended-shmmax The min_free_kbytes here is important. Anti-fragmentation works best when pageblocks don't mix. hugeadm knows how to calculate a value that will significantly reduce the worst of external-fragmentation-related events as reported by the mm_page_alloc_extfrag tracepoint. 2. Load up memory a) Start updatedb b) Create in parallel a X files of pagesize*128 in size. Wait until files are created. By parallel, I mean that 4096 instances of dd were launched, one after the other using &. The crude objective being to mix filesystem metadata allocations with the buffer cache. c) Delete every second file so that pageblocks are likely to have holes d) kill updatedb if it's still running At this point, the system is quiet, memory is full but it's full with clean filesystem metadata and clean buffer cache that is unmapped. This is readily migrated or discarded so you'd expect lumpy reclaim to have no significant advantage over compaction but this is at the POC stage. 3. In increments, attempt to allocate 5% of memory as hugepages. Measure how long it took, how successful it was, how many direct reclaims took place and how how many compactions. Note the compaction figures might not fully add up as compactions can take place for orders other than the hugepage size X86 vanilla compaction Final page count 913 916 (attempted 1002) pages reclaimed 68296 9791 X86-64 vanilla compaction Final page count: 901 902 (attempted 1002) Total pages reclaimed: 112599 53234 PPC64 vanilla compaction Final page count: 93 94 (attempted 110) Total pages reclaimed: 103216 61838 There was not a dramatic improvement in success rates but it wouldn't be expected in this case either. What was important is that fewer pages were reclaimed in all cases reducing the amount of IO required to satisfy a huge page allocation. The second tests were all performance related - kernbench, netperf, iozone and sysbench. None showed anything too remarkable. The last test was a high-order allocation stress test. Many kernel compiles are started to fill memory with a pressured mix of unmovable and movable allocations. During this, an attempt is made to allocate 90% of memory as huge pages - one at a time with small delays between attempts to avoid flooding the IO queue. vanilla compaction Percentage of request allocated X86 98 99 Percentage of request allocated X86-64 95 98 Percentage of request allocated PPC64 55 70 This patch: rmap_walk_anon() does not use page_lock_anon_vma() for looking up and locking an anon_vma and it does not appear to have sufficient locking to ensure the anon_vma does not disappear from under it. This patch copies an approach used by KSM to take a reference on the anon_vma while pages are being migrated. This should prevent rmap_walk() running into nasty surprises later because anon_vma has been freed. Signed-off-by: NMel Gorman <mel@csn.ul.ie> Acked-by: NRik van Riel <riel@redhat.com> Cc: Minchan Kim <minchan.kim@gmail.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@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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- 12 5月, 2010 1 次提交
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由 Naoya Horiguchi 提交于
Currently page_address_in_vma() compares vma->anon_vma and page_anon_vma(page) for parameter check, but in 2.6.34 a vma can have multiple anon_vmas with anon_vma_chain, so current check does not work. (For anonymous page shared by multiple processes, some verified (page,vma) pairs return -EFAULT wrongly.) We can go to checking all anon_vmas in the "same_vma" chain, but it needs to meet lock requirement. Instead, we can remove anon_vma check safely because page_address_in_vma() assumes that page and vma are already checked to belong to the identical process. Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com> Reviewed-by: NRik van Riel <riel@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Mel Gorman <mel@csn.ul.ie> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 25 4月, 2010 1 次提交
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由 Oleg Nesterov 提交于
If find_mergeable_anon_vma() succeeds but another thread installs ->anon_vma before we take ptl, then allocated == NULL but avc should be freed. Change the code to check avc != NULL to detect this case. Also, a couple of whitespace changes to make the critical section more visible. Signed-off-by: NOleg Nesterov <oleg@redhat.com> Reviewed-by: NRik van Riel <riel@redhat.com> Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk> Cc: Pete Zaitcev <zaitcev@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 20 4月, 2010 1 次提交
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由 Rik van Riel 提交于
The recent anon_vma fixes cause many anonymous pages to end up in the parent process anon_vma, even when the page is exclusively owned by the current process. Adding exclusively owned anonymous pages to the top anon_vma reduces rmap scanning overhead, especially in workloads with forking servers. This patch adds a parameter to __page_set_anon_rmap that can be used to indicate whether or not the added page is exclusively owned by the current process. Pages added through page_add_new_anon_rmap are exclusively owned by the current process, and can be added to the top anon_vma. Pages added through page_add_anon_rmap can be either shared or exclusively owned, so we do the conservative thing and add it to the oldest anon_vma. A next step would be to add the exclusive parameter to page_add_anon_rmap, to be used from functions where we do know for sure whether a page is exclusively owned. Signed-off-by: NRik van Riel <riel@redhat.com> Reviewed-by: NJohannes Weiner <hannes@cmpxchg.org> Lightly-tested-by: NBorislav Petkov <bp@alien8.de> Reviewed-by: NMinchan Kim <minchan.kim@gmail.com> [ Edited to look nicer - Linus ] Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 13 4月, 2010 2 次提交
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由 Linus Torvalds 提交于
Otherwise we might be mapping in a page in a new mapping, but that page (through the swapcache) would later be mapped into an old mapping too. The page->mapping must be the case that works for everybody, not just the mapping that happened to page it in first. Here's the scenario: - page gets allocated/mapped by process A. Let's call the anon_vma we associate the page with 'A' to keep it easy to track. - Process A forks, creating process B. The anon_vma in B is 'B', and has a chain that looks like 'B' -> 'A'. Everything is fine. - Swapping happens. The page (with mapping pointing to 'A') gets swapped out (perhaps not to disk - it's enough to assume that it's just not mapped any more, and lives entirely in the swap-cache) - Process B pages it in, which goes like this: do_swap_page -> page = lookup_swap_cache(entry); ... set_pte_at(mm, address, page_table, pte); page_add_anon_rmap(page, vma, address); And think about what happens here! In particular, what happens is that this will now be the "first" mapping of that page, so page_add_anon_rmap() used to do if (first) __page_set_anon_rmap(page, vma, address); and notice what anon_vma it will use? It will use the anon_vma for process B! What happens then? Trivial: process 'A' also pages it in (nothing happens, it's not the first mapping), and then process 'B' execve's or exits or unmaps, making anon_vma B go away. End result: process A has a page that points to anon_vma B, but anon_vma B does not exist any more. This can go on forever. Forget about RCU grace periods, forget about locking, forget anything like that. The bug is simply that page->mapping points to an anon_vma that was correct at one point, but was _not_ the one that was shared by all users of that possible mapping. Changing it to always use the deepest anon_vma in the anonvma chain gets us to the safest model. This can be improved in certain cases: if we know the page is private to just this particular mapping (for example, it's a new page, or it is the only swapcache entry), we could pick the top (most specific) anon_vma. But that's a future optimization. Make it _work_ reliably first. Reviewed-by: NRik van Riel <riel@redhat.com> Acked-by: NJohannes Weiner <hannes@cmpxchg.org> Tested-by: Borislav Petkov <bp@alien8.de> [ "What do you know, I think you fixed it!" ] Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Linus Torvalds 提交于
We want to walk the chain in reverse order when cloning it, so that the order of the result chain will be the same as the order in the source chain. When we add entries to the chain, they go at the head of the chain, so we want to add the source head last. Reviewed-by: NRik van Riel <riel@redhat.com> Acked-by: NJohannes Weiner <hannes@cmpxchg.org> Tested-by: Borislav Petkov <bp@alien8.de> [ "No, it still oopses" ] Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 06 4月, 2010 1 次提交
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由 Rik van Riel 提交于
Fix a memory leak in anon_vma_fork(), where we fail to tear down the anon_vmas attached to the new VMA in case setting up the new anon_vma fails. This bug also has the potential to leave behind anon_vma_chain structs with pointers to invalid memory. Reported-by: NMinchan Kim <minchan.kim@gmail.com> Signed-off-by: NRik van Riel <riel@redhat.com> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 07 3月, 2010 7 次提交
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由 Johannes Weiner 提交于
The VM currently assumes that an inactive, mapped and referenced file page is in use and promotes it to the active list. However, every mapped file page starts out like this and thus a problem arises when workloads create a stream of such pages that are used only for a short time. By flooding the active list with those pages, the VM quickly gets into trouble finding eligible reclaim canditates. The result is long allocation latencies and eviction of the wrong pages. This patch reuses the PG_referenced page flag (used for unmapped file pages) to implement a usage detection that scales with the speed of LRU list cycling (i.e. memory pressure). If the scanner encounters those pages, the flag is set and the page cycled again on the inactive list. Only if it returns with another page table reference it is activated. Otherwise it is reclaimed as 'not recently used cache'. This effectively changes the minimum lifetime of a used-once mapped file page from a full memory cycle to an inactive list cycle, which allows it to occur in linear streams without affecting the stable working set of the system. Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org> Reviewed-by: NRik van Riel <riel@redhat.com> Cc: Minchan Kim <minchan.kim@gmail.com> Cc: OSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Rik van Riel 提交于
When a VMA is in an inconsistent state during setup or teardown, the worst that can happen is that the rmap code will not be able to find the page. The mapping is in the process of being torn down (PTEs just got invalidated by munmap), or set up (no PTEs have been instantiated yet). It is also impossible for the rmap code to follow a pointer to an already freed VMA, because the rmap code holds the anon_vma->lock, which the VMA teardown code needs to take before the VMA is removed from the anon_vma chain. Hence, we should not need the VM_LOCK_RMAP locking at all. Signed-off-by: NRik van Riel <riel@redhat.com> Cc: Nick Piggin <npiggin@suse.de> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Larry Woodman <lwoodman@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Rik van Riel 提交于
When the parent process breaks the COW on a page, both the original which is mapped at child and the new page which is mapped parent end up in that same anon_vma. Generally this won't be a problem, but for some workloads it could preserve the O(N) rmap scanning complexity. A simple fix is to ensure that, when a page which is mapped child gets reused in do_wp_page, because we already are the exclusive owner, the page gets moved to our own exclusive child's anon_vma. Signed-off-by: NRik van Riel <riel@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Larry Woodman <lwoodman@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com> Reviewed-by: NMinchan Kim <minchan.kim@gmail.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Rik van Riel 提交于
When an anonymous page is inherited from a parent process, the vma->anon_vma can differ from the page anon_vma. This can trip up __page_check_anon_rmap, which is indirectly called from do_swap_page(). Remove that obsolete check to prevent an oops. Signed-off-by: NRik van Riel <riel@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Larry Woodman <lwoodman@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com> Reviewed-by: NMinchan Kim <minchan.kim@gmail.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 Rik van Riel 提交于
The old anon_vma code can lead to scalability issues with heavily forking workloads. Specifically, each anon_vma will be shared between the parent process and all its child processes. In a workload with 1000 child processes and a VMA with 1000 anonymous pages per process that get COWed, this leads to a system with a million anonymous pages in the same anon_vma, each of which is mapped in just one of the 1000 processes. However, the current rmap code needs to walk them all, leading to O(N) scanning complexity for each page. This can result in systems where one CPU is walking the page tables of 1000 processes in page_referenced_one, while all other CPUs are stuck on the anon_vma lock. This leads to catastrophic failure for a benchmark like AIM7, where the total number of processes can reach in the tens of thousands. Real workloads are still a factor 10 less process intensive than AIM7, but they are catching up. This patch changes the way anon_vmas and VMAs are linked, which allows us to associate multiple anon_vmas with a VMA. At fork time, each child process gets its own anon_vmas, in which its COWed pages will be instantiated. The parents' anon_vma is also linked to the VMA, because non-COWed pages could be present in any of the children. This reduces rmap scanning complexity to O(1) for the pages of the 1000 child processes, with O(N) complexity for at most 1/N pages in the system. This reduces the average scanning cost in heavily forking workloads from O(N) to 2. The only real complexity in this patch stems from the fact that linking a VMA to anon_vmas now involves memory allocations. This means vma_adjust can fail, if it needs to attach a VMA to anon_vma structures. This in turn means error handling needs to be added to the calling functions. A second source of complexity is that, because there can be multiple anon_vmas, the anon_vma linking in vma_adjust can no longer be done under "the" anon_vma lock. To prevent the rmap code from walking up an incomplete VMA, this patch introduces the VM_LOCK_RMAP VMA flag. This bit flag uses the same slot as the NOMMU VM_MAPPED_COPY, with an ifdef in mm.h to make sure it is impossible to compile a kernel that needs both symbolic values for the same bitflag. Some test results: Without the anon_vma changes, when AIM7 hits around 9.7k users (on a test box with 16GB RAM and not quite enough IO), the system ends up running >99% in system time, with every CPU on the same anon_vma lock in the pageout code. With these changes, AIM7 hits the cross-over point around 29.7k users. This happens with ~99% IO wait time, there never seems to be any spike in system time. The anon_vma lock contention appears to be resolved. [akpm@linux-foundation.org: cleanups] Signed-off-by: NRik van Riel <riel@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Larry Woodman <lwoodman@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com> Cc: Minchan Kim <minchan.kim@gmail.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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由 KAMEZAWA Hiroyuki 提交于
A frequent questions from users about memory management is what numbers of swap ents are user for processes. And this information will give some hints to oom-killer. Besides we can count the number of swapents per a process by scanning /proc/<pid>/smaps, this is very slow and not good for usual process information handler which works like 'ps' or 'top'. (ps or top is now enough slow..) This patch adds a counter of swapents to mm_counter and update is at each swap events. Information is exported via /proc/<pid>/status file as [kamezawa@bluextal memory]$ cat /proc/self/status Name: cat State: R (running) Tgid: 2910 Pid: 2910 PPid: 2823 TracerPid: 0 Uid: 500 500 500 500 Gid: 500 500 500 500 FDSize: 256 Groups: 500 VmPeak: 82696 kB VmSize: 82696 kB VmLck: 0 kB VmHWM: 432 kB VmRSS: 432 kB VmData: 172 kB VmStk: 84 kB VmExe: 48 kB VmLib: 1568 kB VmPTE: 40 kB VmSwap: 0 kB <=============== this. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Reviewed-by: NMinchan Kim <minchan.kim@gmail.com> Reviewed-by: NChristoph Lameter <cl@linux-foundation.org> Cc: Lee Schermerhorn <lee.schermerhorn@hp.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 KAMEZAWA Hiroyuki 提交于
Presently, per-mm statistics counter is defined by macro in sched.h This patch modifies it to - defined in mm.h as inlinf functions - use array instead of macro's name creation. This patch is for reducing patch size in future patch to modify implementation of per-mm counter. Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Reviewed-by: NMinchan Kim <minchan.kim@gmail.com> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Lee Schermerhorn <lee.schermerhorn@hp.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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- 16 12月, 2009 1 次提交
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由 KAMEZAWA Hiroyuki 提交于
In global VM, FILE_MAPPED is used but memcg uses MAPPED_FILE. This makes grep difficult. Replace memcg's MAPPED_FILE with FILE_MAPPED And in global VM, mapped shared memory is accounted into FILE_MAPPED. But memcg doesn't. fix it. Note: page_is_file_cache() just checks SwapBacked or not. So, we need to check PageAnon. Cc: Balbir Singh <balbir@in.ibm.com> Reviewed-by: NDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@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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