The patch titled
Subject: mm, memcg: don't skip memory guarantee calculations
has been added to the -mm tree. Its filename is
mm-memcg-dont-skip-memory-guarantee-calculations.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-dont-skip-memory-guarantee-calculations.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-dont-skip-memory-guarantee-calculations.patch
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------------------------------------------------------
From: Roman Gushchin <guro@xxxxxx>
Subject: mm, memcg: don't skip memory guarantee calculations
There are two cases when effective memory guarantee calculation is
mistakenly skipped:
1) If memcg is a child of the root cgroup, and the root cgroup is not
root_mem_cgroup (in other words, if the reclaim is targeted).
Top-level memory cgroups are handled specially in
mem_cgroup_protected(), because the root memory cgroup doesn't have
memory guarantee and can't limit its children guarantees. So, all
effective guarantee calculation is skipped. But in case of targeted
reclaim things are different: cgroups, which parent exceeded its memory
limit aren't special.
2) If memcg has no charged memory (memory usage is 0). In this case
mem_cgroup_protected() always returns MEMCG_PROT_NONE, which is correct
and prevents to generate fake memory low events for empty cgroups. But
skipping memory emin/elow calculation is wrong: if there is no global
memory pressure there might be no good chance again, so we can end up
with effective guarantees set to 0 without any reason.
Link: http://lkml.kernel.org/r/20180522132528.23769-2-guro@xxxxxx
Link: http://lkml.kernel.org/r/20180611175418.7007-4-guro@xxxxxx
Signed-off-by: Roman Gushchin <guro@xxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Greg Thelen <gthelen@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff -puN mm/memcontrol.c~mm-memcg-dont-skip-memory-guarantee-calculations mm/memcontrol.c
--- a/mm/memcontrol.c~mm-memcg-dont-skip-memory-guarantee-calculations
+++ a/mm/memcontrol.c
@@ -5477,15 +5477,10 @@ enum mem_cgroup_protection mem_cgroup_pr
if (mem_cgroup_disabled())
return MEMCG_PROT_NONE;
- if (!root)
- root = root_mem_cgroup;
- if (memcg == root)
+ if (memcg == root_mem_cgroup)
return MEMCG_PROT_NONE;
usage = page_counter_read(&memcg->memory);
- if (!usage)
- return MEMCG_PROT_NONE;
-
emin = memcg->memory.min;
elow = memcg->memory.low;
@@ -5494,7 +5489,7 @@ enum mem_cgroup_protection mem_cgroup_pr
if (!parent)
return MEMCG_PROT_NONE;
- if (parent == root)
+ if (parent == root_mem_cgroup)
goto exit;
parent_emin = READ_ONCE(parent->memory.emin);
@@ -5529,6 +5524,12 @@ exit:
memcg->memory.emin = emin;
memcg->memory.elow = elow;
+ if (root && memcg == root)
+ return MEMCG_PROT_NONE;
+
+ if (!usage)
+ return MEMCG_PROT_NONE;
+
if (usage <= emin)
return MEMCG_PROT_MIN;
else if (usage <= elow)
_
Patches currently in -mm which might be from guro@xxxxxx are
mm-fix-null-pointer-dereference-in-mem_cgroup_protected.patch
mm-memcg-propagate-memory-effective-protection-on-setting-memorymin-low.patch
mm-memcg-dont-skip-memory-guarantee-calculations.patch
mm-propagate-memory-effective-protection-on-setting-memorymin-low.patch
mm-dont-skip-memory-guarantee-calculations.patch
mm-dont-skip-memory-guarantee-calculations-fix.patch
selftests-cgroup-add-test-for-memorylow-corner-cases.patch
mm-oom-refactor-the-oom_kill_process-function.patch
mm-implement-mem_cgroup_scan_tasks-for-the-root-memory-cgroup.patch
mm-oom-cgroup-aware-oom-killer.patch
mm-oom-introduce-memoryoom_group.patch
mm-oom-introduce-memoryoom_group-fix.patch
mm-oom-add-cgroup-v2-mount-option-for-cgroup-aware-oom-killer.patch
mm-oom-docs-describe-the-cgroup-aware-oom-killer.patch
mm-oom-docs-describe-the-cgroup-aware-oom-killer-fix.patch
cgroup-list-groupoom-in-cgroup-features.patch
mm-fix-oom_kill-event-handling.patch
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