linux-stable.git/mm/page_alloc.c, branch v4.10.2

mm/page_alloc: fix nodes for reclaim in fast path

2017-03-12T05:44:10+00:00

commit e02dc017c3032dcdce1b993af0db135462e1b4b7 upstream.

When @node_reclaim_node isn't 0, the page allocator tries to reclaim
pages if the amount of free memory in the zones are below the low
watermark.  On Power platform, none of NUMA nodes are scanned for page
reclaim because no nodes match the condition in zone_allows_reclaim().
On Power platform, RECLAIM_DISTANCE is set to 10 which is the distance
of Node-A to Node-A.  So the preferred node even won't be scanned for
page reclaim.

   __alloc_pages_nodemask()
   get_page_from_freelist()
      zone_allows_reclaim()

Anton proposed the test code as below:

   # cat alloc.c
      :
   int main(int argc, char *argv[])
   {
	void *p;
	unsigned long size;
	unsigned long start, end;

	start = time(NULL);
	size = strtoul(argv[1], NULL, 0);
	printf("To allocate %ldGB memory\n", size);

	size <<= 30;
	p = malloc(size);
	assert(p);
	memset(p, 0, size);

	end = time(NULL);
	printf("Used time: %ld seconds\n", end - start);
	sleep(3600);
	return 0;
   }

The system I use for testing has two NUMA nodes.  Both have 128GB
memory.  In below scnario, the page caches on node#0 should be reclaimed
when it encounters pressure to accommodate request of allocation.

   # echo 2 > /proc/sys/vm/zone_reclaim_mode; \
     sync; \
     echo 3 > /proc/sys/vm/drop_caches; \
   # taskset -c 0 cat file.32G > /dev/null; \
     grep FilePages /sys/devices/system/node/node0/meminfo
     Node 0 FilePages:       33619712 kB
   # taskset -c 0 ./alloc 128
   # grep FilePages /sys/devices/system/node/node0/meminfo
     Node 0 FilePages:       33619840 kB
   # grep MemFree /sys/devices/system/node/node0/meminfo
     Node 0 MemFree:          186816 kB

With the patch applied, the pagecache on node-0 is reclaimed when its
free memory is running out.  It's the expected behaviour.

   # echo 2 > /proc/sys/vm/zone_reclaim_mode; \
     sync; \
     echo 3 > /proc/sys/vm/drop_caches
   # taskset -c 0 cat file.32G > /dev/null; \
     grep FilePages /sys/devices/system/node/node0/meminfo
     Node 0 FilePages:       33605568 kB
   # taskset -c 0 ./alloc 128
   # grep FilePages /sys/devices/system/node/node0/meminfo
     Node 0 FilePages:        1379520 kB
   # grep MemFree /sys/devices/system/node/node0/meminfo
     Node 0 MemFree:           317120 kB

Fixes: 5f7a75acdb24 ("mm: page_alloc: do not cache reclaim distances")
Link: http://lkml.kernel.org/r/1486532455-29613-1-git-send-email-gwshan@linux.vnet.ibm.com
Signed-off-by: Gavin Shan 
Acked-by: Mel Gorman 
Acked-by: Michal Hocko 
Cc: Anton Blanchard 
Cc: Michael Ellerman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm, page_alloc: fix premature OOM when racing with cpuset mems update

2017-01-25T00:26:14+00:00

Ganapatrao Kulkarni reported that the LTP test cpuset01 in stress mode
triggers OOM killer in few seconds, despite lots of free memory.  The
test attempts to repeatedly fault in memory in one process in a cpuset,
while changing allowed nodes of the cpuset between 0 and 1 in another
process.

The problem comes from insufficient protection against cpuset changes,
which can cause get_page_from_freelist() to consider all zones as
non-eligible due to nodemask and/or current->mems_allowed.  This was
masked in the past by sufficient retries, but since commit 682a3385e773
("mm, page_alloc: inline the fast path of the zonelist iterator") we fix
the preferred_zoneref once, and don't iterate over the whole zonelist in
further attempts, thus the only eligible zones might be placed in the
zonelist before our starting point and we always miss them.

A previous patch fixed this problem for current->mems_allowed.  However,
cpuset changes also update the task's mempolicy nodemask.  The fix has
two parts.  We have to repeat the preferred_zoneref search when we
detect cpuset update by way of seqcount, and we have to check the
seqcount before considering OOM.

[akpm@linux-foundation.org: fix typo in comment]
Link: http://lkml.kernel.org/r/20170120103843.24587-5-vbabka@suse.cz
Fixes: c33d6c06f60f ("mm, page_alloc: avoid looking up the first zone in a zonelist twice")
Signed-off-by: Vlastimil Babka 
Reported-by: Ganapatrao Kulkarni 
Acked-by: Mel Gorman 
Acked-by: Hillf Danton 
Cc: Michal Hocko 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, page_alloc: move cpuset seqcount checking to slowpath

2017-01-25T00:26:14+00:00

This is a preparation for the following patch to make review simpler.
While the primary motivation is a bug fix, this also simplifies the fast
path, although the moved code is only enabled when cpusets are in use.

Link: http://lkml.kernel.org/r/20170120103843.24587-4-vbabka@suse.cz
Signed-off-by: Vlastimil Babka 
Acked-by: Mel Gorman 
Acked-by: Hillf Danton 
Cc: Ganapatrao Kulkarni 
Cc: Michal Hocko 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, page_alloc: fix fast-path race with cpuset update or removal

2017-01-25T00:26:14+00:00

Ganapatrao Kulkarni reported that the LTP test cpuset01 in stress mode
triggers OOM killer in few seconds, despite lots of free memory.  The
test attempts to repeatedly fault in memory in one process in a cpuset,
while changing allowed nodes of the cpuset between 0 and 1 in another
process.

One possible cause is that in the fast path we find the preferred
zoneref according to current mems_allowed, so that it points to the
middle of the zonelist, skipping e.g.  zones of node 1 completely.  If
the mems_allowed is updated to contain only node 1, we never reach it in
the zonelist, and trigger OOM before checking the cpuset_mems_cookie.

This patch fixes the particular case by redoing the preferred zoneref
search if we switch back to the original nodemask.  The condition is
also slightly changed so that when the last non-root cpuset is removed,
we don't miss it.

Note that this is not a full fix, and more patches will follow.

Link: http://lkml.kernel.org/r/20170120103843.24587-3-vbabka@suse.cz
Fixes: 682a3385e773 ("mm, page_alloc: inline the fast path of the zonelist iterator")
Signed-off-by: Vlastimil Babka 
Reported-by: Ganapatrao Kulkarni 
Acked-by: Michal Hocko 
Acked-by: Mel Gorman 
Acked-by: Hillf Danton 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, page_alloc: fix check for NULL preferred_zone

2017-01-25T00:26:14+00:00

Patch series "fix premature OOM regression in 4.7+ due to cpuset races".

This is v2 of my attempt to fix the recent report based on LTP cpuset
stress test [1].  The intention is to go to stable 4.9 LTSS with this,
as triggering repeated OOMs is not nice.  That's why the patches try to
be not too intrusive.

Unfortunately why investigating I found that modifying the testcase to
use per-VMA policies instead of per-task policies will bring the OOM's
back, but that seems to be much older and harder to fix problem.  I have
posted a RFC [2] but I believe that fixing the recent regressions has a
higher priority.

Longer-term we might try to think how to fix the cpuset mess in a better
and less error prone way.  I was for example very surprised to learn,
that cpuset updates change not only task->mems_allowed, but also
nodemask of mempolicies.  Until now I expected the parameter to
alloc_pages_nodemask() to be stable.  I wonder why do we then treat
cpusets specially in get_page_from_freelist() and distinguish HARDWALL
etc, when there's unconditional intersection between mempolicy and
cpuset.  I would expect the nodemask adjustment for saving overhead in
g_p_f(), but that clearly doesn't happen in the current form.  So we
have both crazy complexity and overhead, AFAICS.

[1] https://lkml.kernel.org/r/CAFpQJXUq-JuEP=QPidy4p_=FN0rkH5Z-kfB4qBvsf6jMS87Edg@mail.gmail.com
[2] https://lkml.kernel.org/r/7c459f26-13a6-a817-e508-b65b903a8378@suse.cz

This patch (of 4):

Since commit c33d6c06f60f ("mm, page_alloc: avoid looking up the first
zone in a zonelist twice") we have a wrong check for NULL preferred_zone,
which can theoretically happen due to concurrent cpuset modification.  We
check the zoneref pointer which is never NULL and we should check the zone
pointer.  Also document this in first_zones_zonelist() comment per Michal
Hocko.

Fixes: c33d6c06f60f ("mm, page_alloc: avoid looking up the first zone in a zonelist twice")
Link: http://lkml.kernel.org/r/20170120103843.24587-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka 
Acked-by: Mel Gorman 
Acked-by: Hillf Danton 
Cc: Ganapatrao Kulkarni 
Cc: Michal Hocko 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: alloc_contig: re-allow CMA to compact FS pages

2017-01-25T00:26:14+00:00

Commit 73e64c51afc5 ("mm, compaction: allow compaction for GFP_NOFS
requests") changed compation to skip FS pages if not explicitly allowed
to touch them, but missed to update the CMA compact_control.

This leads to a very high isolation failure rate, crippling performance
of CMA even on a lightly loaded system.  Re-allow CMA to compact FS
pages by setting the correct GFP flags, restoring CMA behavior and
performance to the kernel 4.9 level.

Fixes: 73e64c51afc5 (mm, compaction: allow compaction for GFP_NOFS requests)
Link: http://lkml.kernel.org/r/20170113115155.24335-1-l.stach@pengutronix.de
Signed-off-by: Lucas Stach 
Acked-by: Michal Hocko 
Acked-by: Vlastimil Babka 
Cc: Joonsoo Kim 
Cc: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: rename __page_frag functions to __page_frag_cache, drop order from drain

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

This patch does two things.

First it goes through and renames the __page_frag prefixed functions to
__page_frag_cache so that we can be clear that we are draining or
refilling the cache, not the frags themselves.

Second we drop the order parameter from __page_frag_cache_drain since we
don't actually need to pass it since all fragments are either order 0 or
must be a compound page.

Link: http://lkml.kernel.org/r/20170104023954.13451.5678.stgit@localhost.localdomain
Signed-off-by: Alexander Duyck 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: rename __alloc_page_frag to page_frag_alloc and __free_page_frag to page_frag_free

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

Patch series "Page fragment updates", v4.

This patch series takes care of a few cleanups for the page fragments
API.

First we do some renames so that things are much more consistent.  First
we move the page_frag_ portion of the name to the front of the functions
names.  Secondly we split out the cache specific functions from the
other page fragment functions by adding the word "cache" to the name.

Finally I added a bit of documentation that will hopefully help to
explain some of this.  I plan to revisit this later as we get things
more ironed out in the near future with the changes planned for the DMA
setup to support eXpress Data Path.

This patch (of 3):

This patch renames the page frag functions to be more consistent with
other APIs.  Specifically we place the name page_frag first in the name
and then have either an alloc or free call name that we append as the
suffix.  This makes it a bit clearer in terms of naming.

In addition we drop the leading double underscores since we are
technically no longer a backing interface and instead the front end that
is called from the networking APIs.

Link: http://lkml.kernel.org/r/20170104023854.13451.67390.stgit@localhost.localdomain
Signed-off-by: Alexander Duyck 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: don't dereference struct page fields of invalid pages

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

The VM_BUG_ON() check in move_freepages() checks whether the node id of
a page matches the node id of its zone.  However, it does this before
having checked whether the struct page pointer refers to a valid struct
page to begin with.  This is guaranteed in most cases, but may not be
the case if CONFIG_HOLES_IN_ZONE=y.

So reorder the VM_BUG_ON() with the pfn_valid_within() check.

Link: http://lkml.kernel.org/r/1481706707-6211-2-git-send-email-ard.biesheuvel@linaro.org
Signed-off-by: Ard Biesheuvel 
Acked-by: Will Deacon 
Cc: Catalin Marinas 
Cc: Hanjun Guo 
Cc: Yisheng Xie 
Cc: Robert Richter 
Cc: James Morse 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: get rid of __GFP_OTHER_NODE

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

The flag was introduced by commit 78afd5612deb ("mm: add
__GFP_OTHER_NODE flag") to allow proper accounting of remote node
allocations done by kernel daemons on behalf of a process - e.g.
khugepaged.

After "mm: fix remote numa hits statistics" we do not need and actually
use the flag so we can safely remove it because all allocations which
are satisfied from their "home" node are accounted properly.

[mhocko@suse.com: fix build]
Link: http://lkml.kernel.org/r/20170106122225.GK5556@dhcp22.suse.cz
Link: http://lkml.kernel.org/r/20170102153057.9451-3-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Acked-by: Mel Gorman 
Acked-by: Vlastimil Babka 
Cc: Michal Hocko 
Cc: Johannes Weiner 
Cc: Joonsoo Kim 
Cc: Taku Izumi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds