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mm: memcontrol: don't count limit-setting reclaim as memory pressure

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Mot-CRs-fixed: (CR)
When an outside process lowers one of the memory limits of a cgroup (or
uses the force_empty knob in cgroup1), direct reclaim is performed in the
context of the write(), in order to directly enforce the new limit and
have it being met by the time the write() returns.

Currently, this reclaim activity is accounted as memory pressure in the
cgroup that the writer(!) belongs to.  This is unexpected.  It
specifically causes problems for senpai
(https://github.com/facebookincubator/senpai), which is an agent that
routinely adjusts the memory limits and performs associated reclaim work
in tens or even hundreds of cgroups running on the host.  The cgroup that
senpai is running in itself will report elevated levels of memory
pressure, even though it itself is under no memory shortage or any sort of
distress.

Move the psi annotation from the central cgroup reclaim function to
callsites in the allocation context, and thereby no longer count any
limit-setting reclaim as memory pressure.  If the newly set limit causes
the workload inside the cgroup into direct reclaim, that of course will
continue to count as memory pressure.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Chris Down <chris@chrisdown.name>
Acked-by: Michal Hocko <mhocko@suse.com>
Link: http://lkml.kernel.org/r/20200728135210.379885-2-hannes@cmpxchg.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Change-Id: I49bbfc4c462e1e42264558566ab495e695d9e00d
Reviewed-on: https://gerrit.mot.com/2771207
SME-Granted: SME Approvals Granted
SLTApproved: Slta Waiver
Tested-by: Jira Key
Reviewed-by: Yonghui Jia <jiayh2@motorola.com>
Reviewed-by: Huosheng Liao <liaohs@motorola.com>
Submit-Approved: Jira Key
This commit is contained in:
Johannes Weiner 2020-08-06 23:22:15 -07:00 • committed by Xiaojun Ji
commit 27abaa391d
2 changed files with 9 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

10
mm/memcontrol.c
View file

@ -2362,10 +2362,15 @@ static void reclaim_high(struct mem_cgroup *memcg,
gfp_t gfp_mask)
{
do {
unsigned long pflags;
if (page_counter_read(&memcg->memory) <= memcg->high)
continue;
memcg_memory_event(memcg, MEMCG_HIGH);
psi_memstall_enter(&pflags);
try_to_free_mem_cgroup_pages(memcg, nr_pages, gfp_mask, true);
psi_memstall_leave(&pflags);
} while ((memcg = parent_mem_cgroup(memcg)));
}
@ -2552,9 +2557,10 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
struct mem_cgroup *mem_over_limit;
struct page_counter *counter;
unsigned long nr_reclaimed;
enum oom_status oom_status;
bool may_swap = true;
bool drained = false;
enum oom_status oom_status;
unsigned long pflags;
if (mem_cgroup_is_root(memcg))
return 0;
@ -2614,8 +2620,10 @@ retry:
memcg_memory_event(mem_over_limit, MEMCG_MAX);
psi_memstall_enter(&pflags);
nr_reclaimed = try_to_free_mem_cgroup_pages(mem_over_limit, nr_pages,
gfp_mask, may_swap);
psi_memstall_leave(&pflags);
if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
goto retry;

3
mm/vmscan.c
View file

@ -3450,7 +3450,6 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
{
struct zonelist *zonelist;
unsigned long nr_reclaimed;
unsigned long pflags;
int nid;
unsigned int noreclaim_flag;
struct scan_control sc = {
@ -3477,13 +3476,11 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask);
psi_memstall_enter(&pflags);
noreclaim_flag = memalloc_noreclaim_save();
nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
memalloc_noreclaim_restore(noreclaim_flag);
psi_memstall_leave(&pflags);
trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
set_task_reclaim_state(current, NULL);