[PATCH memcg 3/3] memcg: handle memcg oom failures
STALE1807d
From: Vasily Averin <hidden>
Date: 2021-10-20 12:14:54
Also in:
linux-mm, lkml
Subsystem:
control group - memory resource controller (memcg), memory management, the rest · Maintainers:
Johannes Weiner, Michal Hocko, Roman Gushchin, Shakeel Butt, Andrew Morton, Linus Torvalds
mem_cgroup_oom() can fail if current task was marked unkillable
and oom killer cannot find any victim.
Currently we force memcg charge for such allocations,
however it allow memcg-limited userspace task in to overuse assigned limits
and potentially trigger the global memory shortage.
Let's fail the memory charge in such cases.
This failure should be somehow recognised in #PF context,
so let's use current->memcg_in_oom == (struct mem_cgroup *)OOM_FAILED
ToDo: what is the best way to notify pagefault_out_of_memory() about
mem_cgroup_out_of_memory failure ?
Signed-off-by: Vasily Averin <redacted>
---
mm/memcontrol.c | 32 +++++++++++++++++++++++---------
1 file changed, 23 insertions(+), 9 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 74a7379dbac1..b09d3c64f63f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c@@ -1810,11 +1810,21 @@ static enum oom_status mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int mem_cgroup_oom_notify(memcg); mem_cgroup_unmark_under_oom(memcg); - if (mem_cgroup_out_of_memory(memcg, mask, order)) + if (mem_cgroup_out_of_memory(memcg, mask, order)) { ret = OOM_SUCCESS; - else + } else { ret = OOM_FAILED; - + /* + * In some rare cases mem_cgroup_out_of_memory() can return false. + * If it was called from #PF it forces handle_mm_fault() + * return VM_FAULT_OOM and executes pagefault_out_of_memory(). + * memcg_in_oom is set here to notify pagefault_out_of_memory() + * that it was a memcg-related failure and not allow to run + * global OOM. + */ + if (current->in_user_fault) + current->memcg_in_oom = (struct mem_cgroup *)ret; + } if (locked) mem_cgroup_oom_unlock(memcg);
@@ -1848,6 +1858,15 @@ bool mem_cgroup_oom_synchronize(bool handle) if (!memcg) return false; + /* OOM is memcg, however out_of_memory() found no victim */ + if (memcg == (struct mem_cgroup *)OOM_FAILED) { + /* + * Should be called from pagefault_out_of_memory() only, + * where it is used to prevent false global OOM. + */ + current->memcg_in_oom = NULL; + return true; + } if (!handle) goto cleanup;
@@ -2633,15 +2652,10 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, */ oom_status = mem_cgroup_oom(mem_over_limit, gfp_mask, get_order(nr_pages * PAGE_SIZE)); - switch (oom_status) { - case OOM_SUCCESS: + if (oom_status == OOM_SUCCESS) { passed_oom = true; nr_retries = MAX_RECLAIM_RETRIES; goto retry; - case OOM_FAILED: - goto force; - default: - goto nomem; } nomem: if (!(gfp_mask & __GFP_NOFAIL))
--
2.32.0