linux-stable.git/mm/internal.h, branch linux-4.7.y

mm, sl[au]b: add __GFP_ATOMIC to the GFP reclaim mask

2016-06-25T00:23:52+00:00

Commit d0164adc89f6 ("mm, page_alloc: distinguish between being unable
to sleep, unwilling to sleep and avoiding waking kswapd") modified
__GFP_WAIT to explicitly identify the difference between atomic callers
and those that were unwilling to sleep.  Later the definition was
removed entirely.

The GFP_RECLAIM_MASK is the set of flags that affect watermark checking
and reclaim behaviour but __GFP_ATOMIC was never added.  Without it,
atomic users of the slab allocator strip the __GFP_ATOMIC flag and
cannot access the page allocator atomic reserves.  This patch addresses
the problem.

The user-visible impact depends on the workload but potentially atomic
allocations unnecessarily fail without this path.

Link: http://lkml.kernel.org/r/20160610093832.GK2527@techsingularity.net
Signed-off-by: Mel Gorman 
Reported-by: Marcin Wojtas 
Acked-by: Vlastimil Babka 
Acked-by: Michal Hocko 
Cc: 	[4.4+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: make vm_mmap killable

2016-05-24T00:04:14+00:00

All the callers of vm_mmap seem to check for the failure already and
bail out in one way or another on the error which means that we can
change it to use killable version of vm_mmap_pgoff and return -EINTR if
the current task gets killed while waiting for mmap_sem.  This also
means that vm_mmap_pgoff can be killable by default and drop the
additional parameter.

This will help in the OOM conditions when the oom victim might be stuck
waiting for the mmap_sem for write which in turn can block oom_reaper
which relies on the mmap_sem for read to make a forward progress and
reclaim the address space of the victim.

Please note that load_elf_binary is ignoring vm_mmap error for
current->personality & MMAP_PAGE_ZERO case but that shouldn't be a
problem because the address is not used anywhere and we never return to
the userspace if we got killed.

Signed-off-by: Michal Hocko 
Acked-by: Vlastimil Babka 
Cc: "Kirill A. Shutemov" 
Cc: Mel Gorman 
Cc: Oleg Nesterov 
Cc: Andrea Arcangeli 
Cc: Al Viro 
Cc: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: make mmap_sem for write waits killable for mm syscalls

2016-05-24T00:04:14+00:00

This is a follow up work for oom_reaper [1].  As the async OOM killing
depends on oom_sem for read we would really appreciate if a holder for
write didn't stood in the way.  This patchset is changing many of
down_write calls to be killable to help those cases when the writer is
blocked and waiting for readers to release the lock and so help
__oom_reap_task to process the oom victim.

Most of the patches are really trivial because the lock is help from a
shallow syscall paths where we can return EINTR trivially and allow the
current task to die (note that EINTR will never get to the userspace as
the task has fatal signal pending).  Others seem to be easy as well as
the callers are already handling fatal errors and bail and return to
userspace which should be sufficient to handle the failure gracefully.
I am not familiar with all those code paths so a deeper review is really
appreciated.

As this work is touching more areas which are not directly connected I
have tried to keep the CC list as small as possible and people who I
believed would be familiar are CCed only to the specific patches (all
should have received the cover though).

This patchset is based on linux-next and it depends on
down_write_killable for rw_semaphores which got merged into tip
locking/rwsem branch and it is merged into this next tree.  I guess it
would be easiest to route these patches via mmotm because of the
dependency on the tip tree but if respective maintainers prefer other
way I have no objections.

I haven't covered all the mmap_write(mm->mmap_sem) instances here

  $ git grep "down_write(.*\)" next/master | wc -l
  98
  $ git grep "down_write(.*\)" | wc -l
  62

I have tried to cover those which should be relatively easy to review in
this series because this alone should be a nice improvement.  Other
places can be changed on top.

[0] http://lkml.kernel.org/r/1456752417-9626-1-git-send-email-mhocko@kernel.org
[1] http://lkml.kernel.org/r/1452094975-551-1-git-send-email-mhocko@kernel.org
[2] http://lkml.kernel.org/r/1456750705-7141-1-git-send-email-mhocko@kernel.org

This patch (of 18):

This is the first step in making mmap_sem write waiters killable.  It
focuses on the trivial ones which are taking the lock early after
entering the syscall and they are not changing state before.

Therefore it is very easy to change them to use down_write_killable and
immediately return with -EINTR.  This will allow the waiter to pass away
without blocking the mmap_sem which might be required to make a forward
progress.  E.g.  the oom reaper will need the lock for reading to
dismantle the OOM victim address space.

The only tricky function in this patch is vm_mmap_pgoff which has many
call sites via vm_mmap.  To reduce the risk keep vm_mmap with the
original non-killable semantic for now.

vm_munmap callers do not bother checking the return value so open code
it into the munmap syscall path for now for simplicity.

Signed-off-by: Michal Hocko 
Acked-by: Vlastimil Babka 
Cc: Mel Gorman 
Cc: "Kirill A. Shutemov" 
Cc: Konstantin Khlebnikov 
Cc: Hugh Dickins 
Cc: Andrea Arcangeli 
Cc: David Rientjes 
Cc: Dave Hansen 
Cc: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, compaction: distinguish between full and partial COMPACT_COMPLETE

2016-05-21T00:58:30+00:00

COMPACT_COMPLETE now means that compaction and free scanner met.  This
is not very useful information if somebody just wants to use this
feedback and make any decisions based on that.  The current caller might
be a poor guy who just happened to scan tiny portion of the zone and
that could be the reason no suitable pages were compacted.  Make sure we
distinguish the full and partial zone walks.

Consumers should treat COMPACT_PARTIAL_SKIPPED as a potential success
and be optimistic in retrying.

The existing users of COMPACT_COMPLETE are conservatively changed to use
COMPACT_PARTIAL_SKIPPED as well but some of them should be probably
reconsidered and only defer the compaction only for COMPACT_COMPLETE
with the new semantic.

This patch shouldn't introduce any functional changes.

Signed-off-by: Michal Hocko 
Acked-by: Vlastimil Babka 
Acked-by: Hillf Danton 
Cc: David Rientjes 
Cc: Johannes Weiner 
Cc: Joonsoo Kim 
Cc: Mel Gorman 
Cc: Tetsuo Handa 
Cc: Vladimir Davydov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, page_alloc: remove field from alloc_context

2016-05-20T02:12:14+00:00

The classzone_idx can be inferred from preferred_zoneref so remove the
unnecessary field and save stack space.

Signed-off-by: Mel Gorman 
Cc: Vlastimil Babka 
Cc: Jesper Dangaard Brouer 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, page_alloc: avoid looking up the first zone in a zonelist twice

2016-05-20T02:12:14+00:00

The allocator fast path looks up the first usable zone in a zonelist and
then get_page_from_freelist does the same job in the zonelist iterator.
This patch preserves the necessary information.

                                             4.6.0-rc2                  4.6.0-rc2
                                        fastmark-v1r20             initonce-v1r20
  Min      alloc-odr0-1               364.00 (  0.00%)           359.00 (  1.37%)
  Min      alloc-odr0-2               262.00 (  0.00%)           260.00 (  0.76%)
  Min      alloc-odr0-4               214.00 (  0.00%)           214.00 (  0.00%)
  Min      alloc-odr0-8               186.00 (  0.00%)           186.00 (  0.00%)
  Min      alloc-odr0-16              173.00 (  0.00%)           173.00 (  0.00%)
  Min      alloc-odr0-32              165.00 (  0.00%)           165.00 (  0.00%)
  Min      alloc-odr0-64              161.00 (  0.00%)           162.00 ( -0.62%)
  Min      alloc-odr0-128             159.00 (  0.00%)           161.00 ( -1.26%)
  Min      alloc-odr0-256             168.00 (  0.00%)           170.00 ( -1.19%)
  Min      alloc-odr0-512             180.00 (  0.00%)           181.00 ( -0.56%)
  Min      alloc-odr0-1024            190.00 (  0.00%)           190.00 (  0.00%)
  Min      alloc-odr0-2048            196.00 (  0.00%)           196.00 (  0.00%)
  Min      alloc-odr0-4096            202.00 (  0.00%)           202.00 (  0.00%)
  Min      alloc-odr0-8192            206.00 (  0.00%)           205.00 (  0.49%)
  Min      alloc-odr0-16384           206.00 (  0.00%)           205.00 (  0.49%)

The benefit is negligible and the results are within the noise but each
cycle counts.

Signed-off-by: Mel Gorman 
Cc: Vlastimil Babka 
Cc: Jesper Dangaard Brouer 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, page_alloc: convert alloc_flags to unsigned

2016-05-20T02:12:14+00:00

alloc_flags is a bitmask of flags but it is signed which does not
necessarily generate the best code depending on the compiler.  Even
without an impact, it makes more sense that this be unsigned.

Signed-off-by: Mel Gorman 
Acked-by: Vlastimil Babka 
Cc: Jesper Dangaard Brouer 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: rename _count, field of the struct page, to _refcount

2016-05-20T02:12:14+00:00

Many developers already know that field for reference count of the
struct page is _count and atomic type.  They would try to handle it
directly and this could break the purpose of page reference count
tracepoint.  To prevent direct _count modification, this patch rename it
to _refcount and add warning message on the code.  After that, developer
who need to handle reference count will find that field should not be
accessed directly.

[akpm@linux-foundation.org: fix comments, per Vlastimil]
[akpm@linux-foundation.org: Documentation/vm/transhuge.txt too]
[sfr@canb.auug.org.au: sync ethernet driver changes]
Signed-off-by: Joonsoo Kim 
Signed-off-by: Stephen Rothwell 
Cc: Vlastimil Babka 
Cc: Hugh Dickins 
Cc: Johannes Berg 
Cc: "David S. Miller" 
Cc: Sunil Goutham 
Cc: Chris Metcalf 
Cc: Manish Chopra 
Cc: Yuval Mintz 
Cc: Tariq Toukan 
Cc: Saeed Mahameed 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, oom: introduce oom reaper

2016-03-25T23:37:42+00:00

This patch (of 5):

This is based on the idea from Mel Gorman discussed during LSFMM 2015
and independently brought up by Oleg Nesterov.

The OOM killer currently allows to kill only a single task in a good
hope that the task will terminate in a reasonable time and frees up its
memory.  Such a task (oom victim) will get an access to memory reserves
via mark_oom_victim to allow a forward progress should there be a need
for additional memory during exit path.

It has been shown (e.g.  by Tetsuo Handa) that it is not that hard to
construct workloads which break the core assumption mentioned above and
the OOM victim might take unbounded amount of time to exit because it
might be blocked in the uninterruptible state waiting for an event (e.g.
lock) which is blocked by another task looping in the page allocator.

This patch reduces the probability of such a lockup by introducing a
specialized kernel thread (oom_reaper) which tries to reclaim additional
memory by preemptively reaping the anonymous or swapped out memory owned
by the oom victim under an assumption that such a memory won't be needed
when its owner is killed and kicked from the userspace anyway.  There is
one notable exception to this, though, if the OOM victim was in the
process of coredumping the result would be incomplete.  This is
considered a reasonable constrain because the overall system health is
more important than debugability of a particular application.

A kernel thread has been chosen because we need a reliable way of
invocation so workqueue context is not appropriate because all the
workers might be busy (e.g.  allocating memory).  Kswapd which sounds
like another good fit is not appropriate as well because it might get
blocked on locks during reclaim as well.

oom_reaper has to take mmap_sem on the target task for reading so the
solution is not 100% because the semaphore might be held or blocked for
write but the probability is reduced considerably wrt.  basically any
lock blocking forward progress as described above.  In order to prevent
from blocking on the lock without any forward progress we are using only
a trylock and retry 10 times with a short sleep in between.  Users of
mmap_sem which need it for write should be carefully reviewed to use
_killable waiting as much as possible and reduce allocations requests
done with the lock held to absolute minimum to reduce the risk even
further.

The API between oom killer and oom reaper is quite trivial.
wake_oom_reaper updates mm_to_reap with cmpxchg to guarantee only
NULL->mm transition and oom_reaper clear this atomically once it is done
with the work.  This means that only a single mm_struct can be reaped at
the time.  As the operation is potentially disruptive we are trying to
limit it to the ncessary minimum and the reaper blocks any updates while
it operates on an mm.  mm_struct is pinned by mm_count to allow parallel
exit_mmap and a race is detected by atomic_inc_not_zero(mm_users).

Signed-off-by: Michal Hocko 
Suggested-by: Oleg Nesterov 
Suggested-by: Mel Gorman 
Acked-by: Mel Gorman 
Acked-by: David Rientjes 
Cc: Mel Gorman 
Cc: Tetsuo Handa 
Cc: Oleg Nesterov 
Cc: Hugh Dickins 
Cc: Andrea Argangeli 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: convert printk(KERN_ to pr_

2016-03-17T22:09:34+00:00

Most of the mm subsystem uses pr_ so make it consistent.

Miscellanea:

 - Realign arguments
 - Add missing newline to format
 - kmemleak-test.c has a "kmemleak: " prefix added to the
   "Kmemleak testing" logging message via pr_fmt

Signed-off-by: Joe Perches 
Acked-by: Tejun Heo 	[percpu]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds