From bc8e51c05ad50a5a0b02114d3cc94d151a332595 Mon Sep 17 00:00:00 2001 From: Shakeel Butt Date: Fri, 7 Nov 2025 15:40:41 -0800 Subject: [PATCH] mm: memcg: dump memcg protection info on oom or alloc failures Currently kernel dumps memory state on oom and allocation failures. One of the question usually raised on those dumps is why the kernel has not reclaimed the reclaimable memory instead of triggering oom. One potential reason is the usage of memory protection provided by memcg. So, let's also dump the memory protected by the memcg in such reports to ease the debugging. Link: https://lkml.kernel.org/r/20251107234041.3632644-1-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt Acked-by: Vlastimil Babka Acked-by: Michal Hocko Cc: Roman Gushchin Cc: Johannes Weiner Cc: Shakeel Butt Cc: Muchun Song Cc: David Rientjes Signed-off-by: Andrew Morton --- include/linux/memcontrol.h | 5 +++++ mm/memcontrol.c | 13 +++++++++++++ mm/oom_kill.c | 1 + mm/page_alloc.c | 1 + 4 files changed, 20 insertions(+) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 8c0f15e5978f..966f7c1a0128 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1764,6 +1764,7 @@ static inline void count_objcg_events(struct obj_cgroup *objcg, bool mem_cgroup_node_allowed(struct mem_cgroup *memcg, int nid); +void mem_cgroup_show_protected_memory(struct mem_cgroup *memcg); #else static inline bool mem_cgroup_kmem_disabled(void) { @@ -1830,6 +1831,10 @@ static inline bool mem_cgroup_node_allowed(struct mem_cgroup *memcg, int nid) { return true; } + +static inline void mem_cgroup_show_protected_memory(struct mem_cgroup *memcg) +{ +} #endif /* CONFIG_MEMCG */ #if defined(CONFIG_MEMCG) && defined(CONFIG_ZSWAP) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 025da46d9959..bfc986da3289 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5635,3 +5635,16 @@ bool mem_cgroup_node_allowed(struct mem_cgroup *memcg, int nid) { return memcg ? cpuset_node_allowed(memcg->css.cgroup, nid) : true; } + +void mem_cgroup_show_protected_memory(struct mem_cgroup *memcg) +{ + if (mem_cgroup_disabled() || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) + return; + + if (!memcg) + memcg = root_mem_cgroup; + + pr_warn("Memory cgroup min protection %lukB -- low protection %lukB", + K(atomic_long_read(&memcg->memory.children_min_usage)*PAGE_SIZE), + K(atomic_long_read(&memcg->memory.children_low_usage)*PAGE_SIZE)); +} diff --git a/mm/oom_kill.c b/mm/oom_kill.c index c145b0feecc1..5eb11fbba704 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -472,6 +472,7 @@ static void dump_header(struct oom_control *oc) if (should_dump_unreclaim_slab()) dump_unreclaimable_slab(); } + mem_cgroup_show_protected_memory(oc->memcg); if (sysctl_oom_dump_tasks) dump_tasks(oc); } diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e4efda1158b2..26be5734253f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3977,6 +3977,7 @@ static void warn_alloc_show_mem(gfp_t gfp_mask, nodemask_t *nodemask) filter &= ~SHOW_MEM_FILTER_NODES; __show_mem(filter, nodemask, gfp_zone(gfp_mask)); + mem_cgroup_show_protected_memory(NULL); } void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)