linux.git/mm/slab.c, branch v4.10

mm/slab.c: fix SLAB freelist randomization duplicate entries

2017-01-11T02:31:55+00:00

This patch fixes a bug in the freelist randomization code.  When a high
random number is used, the freelist will contain duplicate entries.  It
will result in different allocations sharing the same chunk.

It will result in odd behaviours and crashes.  It should be uncommon but
it depends on the machines.  We saw it happening more often on some
machines (every few hours of running tests).

Fixes: c7ce4f60ac19 ("mm: SLAB freelist randomization")
Link: http://lkml.kernel.org/r/20170103181908.143178-1-thgarnie@google.com
Signed-off-by: John Sperbeck 
Signed-off-by: Thomas Garnier 
Cc: Christoph Lameter 
Cc: Pekka Enberg 
Cc: David Rientjes 
Cc: Joonsoo Kim 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'for-4.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

2016-12-13T20:59:57+00:00

Pull workqueue updates from Tejun Heo:
 "Mostly patches to initialize workqueue subsystem earlier and get rid
  of keventd_up().

  The patches were headed for the last merge cycle but got delayed due
  to a bug found late minute, which is fixed now.

  Also, to help debugging, destroy_workqueue() is more chatty now on a
  sanity check failure."

* 'for-4.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: move wq_numa_init() to workqueue_init()
  workqueue: remove keventd_up()
  debugobj, workqueue: remove keventd_up() usage
  slab, workqueue: remove keventd_up() usage
  power, workqueue: remove keventd_up() usage
  tty, workqueue: remove keventd_up() usage
  mce, workqueue: remove keventd_up() usage
  workqueue: make workqueue available early during boot
  workqueue: dump workqueue state on sanity check failures in destroy_workqueue()

mm, slab: maintain total slab count instead of active count

2016-12-13T02:55:07+00:00

Rather than tracking the number of active slabs for each node, track the
total number of slabs.  This is a minor improvement that avoids active
slab tracking when a slab goes from free to partial or partial to free.

For slab debugging, this also removes an explicit free count since it
can easily be inferred by the difference in number of total objects and
number of active objects.

Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1612042020110.115755@chino.kir.corp.google.com
Signed-off-by: David Rientjes 
Suggested-by: Joonsoo Kim 
Cc: Greg Thelen 
Cc: Aruna Ramakrishna 
Cc: Christoph Lameter 
Cc: Pekka Enberg 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, slab: faster active and free stats

2016-12-13T02:55:06+00:00

Reading /proc/slabinfo or monitoring slabtop(1) can become very
expensive if there are many slab caches and if there are very lengthy
per-node partial and/or free lists.

Commit 07a63c41fa1f ("mm/slab: improve performance of gathering slabinfo
stats") addressed the per-node full lists which showed a significant
improvement when no objects were freed.  This patch has the same
motivation and optimizes the remainder of the usecases where there are
very lengthy partial and free lists.

This patch maintains per-node active_slabs (full and partial) and
free_slabs rather than iterating the lists at runtime when reading
/proc/slabinfo.

When allocating 100GB of slab from a test cache where every slab page is
on the partial list, reading /proc/slabinfo (includes all other slab
caches on the system) takes ~247ms on average with 48 samples.

As a result of this patch, the same read takes ~0.856ms on average.

[rientjes@google.com: changelog]
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1611081505240.13403@chino.kir.corp.google.com
Signed-off-by: Greg Thelen 
Signed-off-by: David Rientjes 
Cc: Christoph Lameter 
Cc: Pekka Enberg 
Cc: Joonsoo Kim 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

slub: move synchronize_sched out of slab_mutex on shrink

2016-12-13T02:55:06+00:00

synchronize_sched() is a heavy operation and calling it per each cache
owned by a memory cgroup being destroyed may take quite some time.  What
is worse, it's currently called under the slab_mutex, stalling all works
doing cache creation/destruction.

Actually, there isn't much point in calling synchronize_sched() for each
cache - it's enough to call it just once - after setting cpu_partial for
all caches and before shrinking them.  This way, we can also move it out
of the slab_mutex, which we have to hold for iterating over the slab
cache list.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=172991
Link: http://lkml.kernel.org/r/0a10d71ecae3db00fb4421bcd3f82bcc911f4be4.1475329751.git.vdavydov.dev@gmail.com
Signed-off-by: Vladimir Davydov 
Reported-by: Doug Smythies 
Acked-by: Joonsoo Kim 
Cc: Christoph Lameter 
Cc: David Rientjes 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: Pekka Enberg 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/slab: improve performance of gathering slabinfo stats

2016-10-28T01:43:43+00:00

On large systems, when some slab caches grow to millions of objects (and
many gigabytes), running 'cat /proc/slabinfo' can take up to 1-2
seconds.  During this time, interrupts are disabled while walking the
slab lists (slabs_full, slabs_partial, and slabs_free) for each node,
and this sometimes causes timeouts in other drivers (for instance,
Infiniband).

This patch optimizes 'cat /proc/slabinfo' by maintaining a counter for
total number of allocated slabs per node, per cache.  This counter is
updated when a slab is created or destroyed.  This enables us to skip
traversing the slabs_full list while gathering slabinfo statistics, and
since slabs_full tends to be the biggest list when the cache is large,
it results in a dramatic performance improvement.  Getting slabinfo
statistics now only requires walking the slabs_free and slabs_partial
lists, and those lists are usually much smaller than slabs_full.

We tested this after growing the dentry cache to 70GB, and the
performance improved from 2s to 5ms.

Link: http://lkml.kernel.org/r/1472517876-26814-1-git-send-email-aruna.ramakrishna@oracle.com
Signed-off-by: Aruna Ramakrishna 
Acked-by: David Rientjes 
Cc: Mike Kravetz 
Cc: Christoph Lameter 
Cc: Pekka Enberg 
Cc: David Rientjes 
Cc: Joonsoo Kim 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/slab: fix kmemcg cache creation delayed issue

2016-10-28T01:43:42+00:00

There is a bug report that SLAB makes extreme load average due to over
2000 kworker thread.

  https://bugzilla.kernel.org/show_bug.cgi?id=172981

This issue is caused by kmemcg feature that try to create new set of
kmem_caches for each memcg.  Recently, kmem_cache creation is slowed by
synchronize_sched() and futher kmem_cache creation is also delayed since
kmem_cache creation is synchronized by a global slab_mutex lock.  So,
the number of kworker that try to create kmem_cache increases quietly.

synchronize_sched() is for lockless access to node's shared array but
it's not needed when a new kmem_cache is created.  So, this patch rules
out that case.

Fixes: 801faf0db894 ("mm/slab: lockless decision to grow cache")
Link: http://lkml.kernel.org/r/1475734855-4837-1-git-send-email-iamjoonsoo.kim@lge.com
Reported-by: Doug Smythies 
Tested-by: Doug Smythies 
Signed-off-by: Joonsoo Kim 
Cc: Christoph Lameter 
Cc: Pekka Enberg 
Cc: David Rientjes 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'for-4.9' into for-4.10

2016-10-19T16:12:40+00:00

slab, workqueue: remove keventd_up() usage

2016-09-17T17:18:21+00:00

Now that workqueue can handle work item queueing from very early
during boot, there is no need to gate schedule_delayed_work_on() while
!keventd_up().  Remove it.

Signed-off-by: Tejun Heo 
Cc: Christoph Lameter 
Cc: Pekka Enberg 
Cc: David Rientjes 
Cc: Joonsoo Kim 
Cc: Andrew Morton 
Cc: linux-mm@kvack.org

slab: Convert to hotplug state machine

2016-09-06T16:30:20+00:00

Install the callbacks via the state machine.

Signed-off-by: Richard Weinberger 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Sebastian Andrzej Siewior 
Reviewed-by: Sebastian Andrzej Siewior 
Cc: Peter Zijlstra 
Cc: Pekka Enberg 
Cc: linux-mm@kvack.org
Cc: rt@linutronix.de
Cc: David Rientjes 
Cc: Joonsoo Kim 
Cc: Andrew Morton 
Cc: Christoph Lameter 
Link: http://lkml.kernel.org/r/20160823125319.abeapfjapf2kfezp@linutronix.de
Signed-off-by: Thomas Gleixner