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  1. 04 12月, 2014 1 次提交
    • H
      mm: fix swapoff hang after page migration and fork · 2022b4d1
      由 Hugh Dickins 提交于 
      I've been seeing swapoff hangs in recent testing: it's cycling around
trying unsuccessfully to find an mm for some remaining pages of swap.

I have been exercising swap and page migration more heavily recently,
and now notice a long-standing error in copy_one_pte(): it's trying to
add dst_mm to swapoff's mmlist when it finds a swap entry, but is doing
so even when it's a migration entry or an hwpoison entry.

Which wouldn't matter much, except it adds dst_mm next to src_mm,
assuming src_mm is already on the mmlist: which may not be so.  Then if
pages are later swapped out from dst_mm, swapoff won't be able to find
where to replace them.

There's already a !non_swap_entry() test for stats: move that up before
the swap_duplicate() and the addition to mmlist.
Signed-off-by: NHugh Dickins <hughd@google.com>
Cc: Kelley Nielsen <kelleynnn@gmail.com>
Cc: <stable@vger.kernel.org>	[2.6.18+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2022b4d1
  3. 29 10月, 2014 1 次提交
    • W
      zap_pte_range: update addr when forcing flush after TLB batching faiure · ce9ec37b
      由 Will Deacon 提交于 
      When unmapping a range of pages in zap_pte_range, the page being
unmapped is added to an mmu_gather_batch structure for asynchronous
freeing. If we run out of space in the batch structure before the range
has been completely unmapped, then we break out of the loop, force a
TLB flush and free the pages that we have batched so far. If there are
further pages to unmap, then we resume the loop where we left off.

Unfortunately, we forget to update addr when we break out of the loop,
which causes us to truncate the range being invalidated as the end
address is exclusive. When we re-enter the loop at the same address, the
page has already been freed and the pte_present test will fail, meaning
that we do not reconsider the address for invalidation.

This patch fixes the problem by incrementing addr by the PAGE_SIZE
before breaking out of the loop on batch failure.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Cc: stable@vger.kernel.org
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      ce9ec37b
  5. 14 10月, 2014 1 次提交
    • P
      mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared · 64e45507
      由 Peter Feiner 提交于 
      For VMAs that don't want write notifications, PTEs created for read faults
have their write bit set.  If the read fault happens after VM_SOFTDIRTY is
cleared, then the PTE's softdirty bit will remain clear after subsequent
writes.

Here's a simple code snippet to demonstrate the bug:

  char* m = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE,
                 MAP_ANONYMOUS | MAP_SHARED, -1, 0);
  system("echo 4 > /proc/$PPID/clear_refs"); /* clear VM_SOFTDIRTY */
  assert(*m == '\0');     /* new PTE allows write access */
  assert(!soft_dirty(x));
  *m = 'x';               /* should dirty the page */
  assert(soft_dirty(x));  /* fails */

With this patch, write notifications are enabled when VM_SOFTDIRTY is
cleared.  Furthermore, to avoid unnecessary faults, write notifications
are disabled when VM_SOFTDIRTY is set.

As a side effect of enabling and disabling write notifications with
care, this patch fixes a bug in mprotect where vm_page_prot bits set by
drivers were zapped on mprotect.  An analogous bug was fixed in mmap by
commit c9d0bf24 ("mm: uncached vma support with writenotify").
Signed-off-by: NPeter Feiner <pfeiner@google.com>
Reported-by: NPeter Feiner <pfeiner@google.com>
Suggested-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Jamie Liu <jamieliu@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      64e45507
  7. 26 9月, 2014 1 次提交
  9. 14 9月, 2014 1 次提交
  11. 30 8月, 2014 1 次提交
    • H
      x86,mm: fix pte_special versus pte_numa · b38af472
      由 Hugh Dickins 提交于 
      Sasha Levin has shown oopses on ffffea0003480048 and ffffea0003480008 at
mm/memory.c:1132, running Trinity on different 3.16-rc-next kernels:
where zap_pte_range() checks page->mapping to see if PageAnon(page).

Those addresses fit struct pages for pfns d2001 and d2000, and in each
dump a register or a stack slot showed d2001730 or d2000730: pte flags
0x730 are PCD ACCESSED PROTNONE SPECIAL IOMAP; and Sasha's e820 map has
a hole between cfffffff and 100000000, which would need special access.

Commit c46a7c81 ("x86: define _PAGE_NUMA by reusing software bits on
the PMD and PTE levels") has broken vm_normal_page(): a PROTNONE SPECIAL
pte no longer passes the pte_special() test, so zap_pte_range() goes on
to try to access a non-existent struct page.

Fix this by refining pte_special() (SPECIAL with PRESENT or PROTNONE) to
complement pte_numa() (SPECIAL with neither PRESENT nor PROTNONE).  A
hint that this was a problem was that c46a7c81 added pte_numa() test
to vm_normal_page(), and moved its is_zero_pfn() test from slow to fast
path: This was papering over a pte_special() snag when the zero page was
encountered during zap.  This patch reverts vm_normal_page() to how it
was before, relying on pte_special().

It still appears that this patch may be incomplete: aren't there other
places which need to be handling PROTNONE along with PRESENT?  For
example, pte_mknuma() clears _PAGE_PRESENT and sets _PAGE_NUMA, but on a
PROT_NONE area, that would make it pte_special().  This is side-stepped
by the fact that NUMA hinting faults skipped PROT_NONE VMAs and there
are no grounds where a NUMA hinting fault on a PROT_NONE VMA would be
interesting.

Fixes: c46a7c81 ("x86: define _PAGE_NUMA by reusing software bits on the PMD and PTE levels")
Reported-by: NSasha Levin <sasha.levin@oracle.com>
Tested-by: NSasha Levin <sasha.levin@oracle.com>
Signed-off-by: NHugh Dickins <hughd@google.com>
Signed-off-by: NMel Gorman <mgorman@suse.de>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: <stable@vger.kernel.org>	[3.16]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b38af472
  13. 09 8月, 2014 3 次提交
    • A
      arm64,ia64,ppc,s390,sh,tile,um,x86,mm: remove default gate area · a6c19dfe
      由 Andy Lutomirski 提交于 
      The core mm code will provide a default gate area based on
FIXADDR_USER_START and FIXADDR_USER_END if
!defined(__HAVE_ARCH_GATE_AREA) && defined(AT_SYSINFO_EHDR).

This default is only useful for ia64.  arm64, ppc, s390, sh, tile, 64-bit
UML, and x86_32 have their own code just to disable it.  arm, 32-bit UML,
and x86_64 have gate areas, but they have their own implementations.

This gets rid of the default and moves the code into ia64.

This should save some code on architectures without a gate area: it's now
possible to inline the gate_area functions in the default case.
Signed-off-by: NAndy Lutomirski <luto@amacapital.net>
Acked-by: NNathan Lynch <nathan_lynch@mentor.com>
Acked-by: NH. Peter Anvin <hpa@linux.intel.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> [in principle]
Acked-by: Richard Weinberger <richard@nod.at> [for um]
Acked-by: Will Deacon <will.deacon@arm.com> [for arm64]
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Nathan Lynch <Nathan_Lynch@mentor.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a6c19dfe
    • J
      mm: memcontrol: rewrite uncharge API · 0a31bc97
      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>
      0a31bc97
    • J
      mm: memcontrol: rewrite charge API · 00501b53
      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>
      00501b53
  15. 07 8月, 2014 7 次提交
  17. 31 7月, 2014 1 次提交
  19. 24 7月, 2014 1 次提交
  21. 05 6月, 2014 5 次提交
  23. 07 5月, 2014 1 次提交
  25. 26 4月, 2014 1 次提交
    • L
      mm: split 'tlb_flush_mmu()' into tlb flushing and memory freeing parts · 1cf35d47
      由 Linus Torvalds 提交于 
      The mmu-gather operation 'tlb_flush_mmu()' has done two things: the
actual tlb flush operation, and the batched freeing of the pages that
the TLB entries pointed at.

This splits the operation into separate phases, so that the forced
batched flushing done by zap_pte_range() can now do the actual TLB flush
while still holding the page table lock, but delay the batched freeing
of all the pages to after the lock has been dropped.

This in turn allows us to avoid a race condition between
set_page_dirty() (as called by zap_pte_range() when it finds a dirty
shared memory pte) and page_mkclean(): because we now flush all the
dirty page data from the TLB's while holding the pte lock,
page_mkclean() will be held up walking the (recently cleaned) page
tables until after the TLB entries have been flushed from all CPU's.
Reported-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Tested-by: NDave Hansen <dave.hansen@intel.com>
Acked-by: NHugh Dickins <hughd@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      1cf35d47
  27. 23 4月, 2014 1 次提交
    • L
      mm: make fixup_user_fault() check the vma access rights too · 1b17844b
      由 Linus Torvalds 提交于 
      fixup_user_fault() is used by the futex code when the direct user access
fails, and the futex code wants it to either map in the page in a usable
form or return an error.  It relied on handle_mm_fault() to map the
page, and correctly checked the error return from that, but while that
does map the page, it doesn't actually guarantee that the page will be
mapped with sufficient permissions to be then accessed.

So do the appropriate tests of the vma access rights by hand.

[ Side note: arguably handle_mm_fault() could just do that itself, but
  we have traditionally done it in the caller, because some callers -
  notably get_user_pages() - have been able to access pages even when
  they are mapped with PROT_NONE.  Maybe we should re-visit that design
  decision, but in the meantime this is the minimal patch. ]

Found by Dave Jones running his trinity tool.
Reported-by: NDave Jones <davej@redhat.com>
Acked-by: NHugh Dickins <hughd@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      1b17844b
  29. 08 4月, 2014 5 次提交
    • M
      mm: remove unused arg of set_page_dirty_balance() · ed6d7c8e
      由 Miklos Szeredi 提交于 
      There's only one caller of set_page_dirty_balance() and that will call it
with page_mkwrite == 0.

The page_mkwrite argument was unused since commit b827e496 "mm: close
page_mkwrite races".
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      ed6d7c8e
    • M
      memcg: rename high level charging functions · d715ae08
      由 Michal Hocko 提交于 
      mem_cgroup_newpage_charge is used only for charging anonymous memory so
it is better to rename it to mem_cgroup_charge_anon.

mem_cgroup_cache_charge is used for file backed memory so rename it to
mem_cgroup_charge_file.
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d715ae08
    • K
      mm: add debugfs tunable for fault_around_order · 1592eef0
      由 Kirill A. Shutemov 提交于 
      Let's allow people to tweak faultaround at runtime.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ning Qu <quning@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      1592eef0
    • K
      mm: introduce vm_ops->map_pages() · 8c6e50b0
      由 Kirill A. Shutemov 提交于 
      Here's new version of faultaround patchset.  It took a while to tune it
and collect performance data.

First patch adds new callback ->map_pages to vm_operations_struct.

->map_pages() is called when VM asks to map easy accessible pages.
Filesystem should find and map pages associated with offsets from
"pgoff" till "max_pgoff".  ->map_pages() is called with page table
locked and must not block.  If it's not possible to reach a page without
blocking, filesystem should skip it.  Filesystem should use do_set_pte()
to setup page table entry.  Pointer to entry associated with offset
"pgoff" is passed in "pte" field in vm_fault structure.  Pointers to
entries for other offsets should be calculated relative to "pte".

Currently VM use ->map_pages only on read page fault path.  We try to
map FAULT_AROUND_PAGES a time.  FAULT_AROUND_PAGES is 16 for now.
Performance data for different FAULT_AROUND_ORDER is below.

TODO:
 - implement ->map_pages() for shmem/tmpfs;
 - modify get_user_pages() to be able to use ->map_pages() and implement
   mmap(MAP_POPULATE|MAP_NONBLOCK) on top.

=========================================================================
Tested on 4-socket machine (120 threads) with 128GiB of RAM.

Few real-world workloads. The sweet spot for FAULT_AROUND_ORDER here is
somewhere between 3 and 5. Let's say 4 :)

Linux build (make -j60)
FAULT_AROUND_ORDER		Baseline	1		3		4		5		7		9
	minor-faults		283,301,572	247,151,987	212,215,789	204,772,882	199,568,944	194,703,779	193,381,485
	time, seconds		151.227629483	153.920996480	151.356125472	150.863792049	150.879207877	151.150764954	151.450962358
Linux rebuild (make -j60)
FAULT_AROUND_ORDER		Baseline	1		3		4		5		7		9
	minor-faults		5,396,854	4,148,444	2,855,286	2,577,282	2,361,957	2,169,573	2,112,643
	time, seconds		27.404543757	27.559725591	27.030057426	26.855045126	26.678618635	26.974523490	26.761320095
Git test suite (make -j60 test)
FAULT_AROUND_ORDER		Baseline	1		3		4		5		7		9
	minor-faults		129,591,823	99,200,751	66,106,718	57,606,410	51,510,808	45,776,813	44,085,515
	time, seconds		66.087215026	64.784546905	64.401156567	65.282708668	66.034016829	66.793780811	67.237810413

Two synthetic tests: access every word in file in sequential/random order.
It doesn't improve much after FAULT_AROUND_ORDER == 4.

Sequential access 16GiB file
FAULT_AROUND_ORDER		Baseline	1		3		4		5		7		9
 1 thread
	minor-faults		4,195,437	2,098,275	525,068		262,251		131,170		32,856		8,282
	time, seconds		7.250461742	6.461711074	5.493859139	5.488488147	5.707213983	5.898510832	5.109232856
 8 threads
	minor-faults		33,557,540	16,892,728	4,515,848	2,366,999	1,423,382	442,732		142,339
	time, seconds		16.649304881	9.312555263	6.612490639	6.394316732	6.669827501	6.75078944	6.371900528
 32 threads
	minor-faults		134,228,222	67,526,810	17,725,386	9,716,537	4,763,731	1,668,921	537,200
	time, seconds		49.164430543	29.712060103	12.938649729	10.175151004	11.840094583	9.594081325	9.928461797
 60 threads
	minor-faults		251,687,988	126,146,952	32,919,406	18,208,804	10,458,947	2,733,907	928,217
	time, seconds		86.260656897	49.626551828	22.335007632	17.608243696	16.523119035	16.339489186	16.326390902
 120 threads
	minor-faults		503,352,863	252,939,677	67,039,168	35,191,827	19,170,091	4,688,357	1,471,862
	time, seconds		124.589206333	79.757867787	39.508707872	32.167281632	29.972989292	28.729834575	28.042251622
Random access 1GiB file
 1 thread
	minor-faults		262,636		132,743		34,369		17,299		8,527		3,451		1,222
	time, seconds		15.351890914	16.613802482	16.569227308	15.179220992	16.557356122	16.578247824	15.365266994
 8 threads
	minor-faults		2,098,948	1,061,871	273,690		154,501		87,110		25,663		7,384
	time, seconds		15.040026343	15.096933500	14.474757288	14.289129964	14.411537468	14.296316837	14.395635804
 32 threads
	minor-faults		8,390,734	4,231,023	1,054,432	528,847		269,242		97,746		26,881
	time, seconds		20.430433109	21.585235358	22.115062928	14.872878951	14.880856305	14.883370649	14.821261690
 60 threads
	minor-faults		15,733,258	7,892,809	1,973,393	988,266		594,789		164,994		51,691
	time, seconds		26.577302548	25.692397770	18.728863715	20.153026398	21.619101933	17.745086260	17.613215273
 120 threads
	minor-faults		31,471,111	15,816,616	3,959,209	1,978,685	1,008,299	264,635		96,010
	time, seconds		41.835322703	40.459786095	36.085306105	35.313894834	35.814445675	36.552633793	34.289210594

Touch only one page in page table in 16GiB file
FAULT_AROUND_ORDER		Baseline	1		3		4		5		7		9
 1 thread
	minor-faults		8,372		8,324		8,270		8,260		8,249		8,239		8,237
	time, seconds		0.039892712	0.045369149	0.051846126	0.063681685	0.079095975	0.17652406	0.541213386
 8 threads
	minor-faults		65,731		65,681		65,628		65,620		65,608		65,599		65,596
	time, seconds		0.124159196	0.488600638	0.156854426	0.191901957	0.242631486	0.543569456	1.677303984
 32 threads
	minor-faults		262,388		262,341		262,285		262,276		262,266		262,257		263,183
	time, seconds		0.452421421	0.488600638	0.565020946	0.648229739	0.789850823	1.651584361	5.000361559
 60 threads
	minor-faults		491,822		491,792		491,723		491,711		491,701		491,691		491,825
	time, seconds		0.763288616	0.869620515	0.980727360	1.161732354	1.466915814	3.04041448	9.308612938
 120 threads
	minor-faults		983,466		983,655		983,366		983,372		983,363		984,083		984,164
	time, seconds		1.595846553	1.667902182	2.008959376	2.425380942	2.941368804	5.977807890	18.401846125

This patch (of 2):

Introduce new vm_ops callback ->map_pages() and uses it for mapping easy
accessible pages around fault address.

On read page fault, if filesystem provides ->map_pages(), we try to map up
to FAULT_AROUND_PAGES pages around page fault address in hope to reduce
number of minor page faults.

We call ->map_pages first and use ->fault() as fallback if page by the
offset is not ready to be mapped (cold page cache or something).
Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ning Qu <quning@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      8c6e50b0
    • D
      mm/memory.c: update comment in unmap_single_vma() · 7aa6b4ad
      由 Davidlohr Bueso 提交于 
      The described issue now occurs inside mmap_region().  And unfortunately
is still valid.
Signed-off-by: NDavidlohr Bueso <davidlohr@hp.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      7aa6b4ad
  31. 05 4月, 2014 1 次提交
    • H
      mm: get_user_pages(write,force) refuse to COW in shared areas · cda540ac
      由 Hugh Dickins 提交于 
      get_user_pages(write=1, force=1) has always had odd behaviour on write-
protected shared mappings: although it demands FMODE_WRITE-access to the
underlying object (do_mmap_pgoff sets neither VM_SHARED nor VM_MAYWRITE
without that), it ends up with do_wp_page substituting private anonymous
Copied-On-Write pages for the shared file pages in the area.

That was long ago intentional, as a safety measure to prevent ptrace
setting a breakpoint (or POKETEXT or POKEDATA) from inadvertently
corrupting the underlying executable.  Yet exec and dynamic loaders open
the file read-only, and use MAP_PRIVATE rather than MAP_SHARED.

The traditional odd behaviour still causes surprises and bugs in mm, and
is probably not what any caller wants - even the comment on the flag
says "You do not want this" (although it's undoubtedly necessary for
overriding userspace protections in some contexts, and good when !write).

Let's stop doing that.  But it would be dangerous to remove the long-
standing safety at this stage, so just make get_user_pages(write,force)
fail with EFAULT when applied to a write-protected shared area.
Infiniband may in future want to force write through to underlying
object: we can add another FOLL_flag later to enable that if required.

Odd though the old behaviour was, there is no doubt that we may turn out
to break userspace with this change, and have to revert it quickly.
Issue a WARN_ON_ONCE to help debug the changed case (easily triggered by
userspace, so only once to prevent spamming the logs); and delay a few
associated cleanups until this change is proved.

get_user_pages callers who might see trouble from this change:
  ptrace poking, or writing to /proc/<pid>/mem
  drivers/infiniband/
  drivers/media/v4l2-core/
  drivers/gpu/drm/exynos/exynos_drm_gem.c
  drivers/staging/tidspbridge/core/tiomap3430.c
if they ever apply get_user_pages to write-protected shared mappings
of an object which was opened for writing.

I went to apply the same change to mm/nommu.c, but retreated.  NOMMU has
no place for COW, and its VM_flags conventions are not the same: I'd be
more likely to screw up NOMMU than make an improvement there.
Suggested-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NHugh Dickins <hughd@google.com>
Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      cda540ac
  33. 04 4月, 2014 8 次提交