The patch titled Subject: mm, memcg: don't skip memory guarantee calculations has been added to the -mm tree. Its filename is mm-dont-skip-memory-guarantee-calculations.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-dont-skip-memory-guarantee-calculations.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-dont-skip-memory-guarantee-calculations.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ 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 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-dont-skip-memory-guarantee-calculations mm/memcontrol.c --- a/mm/memcontrol.c~mm-dont-skip-memory-guarantee-calculations +++ a/mm/memcontrol.c @@ -5809,20 +5809,15 @@ 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; parent = parent_mem_cgroup(memcg); - if (parent == root) + if (parent == root_mem_cgroup) goto exit; parent_emin = READ_ONCE(parent->memory.emin); @@ -5857,6 +5852,12 @@ 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-rename-page_counters-count-limit-into-usage-max.patch mm-memorylow-hierarchical-behavior.patch mm-treat-memorylow-value-inclusive.patch mm-docs-describe-memorylow-refinements.patch mm-introduce-memorymin.patch mm-introduce-memorymin-fix.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 mm-propagate-memory-effective-protection-on-setting-memorymin-low.patch mm-dont-skip-memory-guarantee-calculations.patch selftests-cgroup-add-test-for-memorylow-corner-cases.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html