From: Yueyang Pan Date: Wed, 3 Sep 2025 11:16:13 +0000 (-0700) Subject: mm/show_mem: dump the status of the mem alloc profiling before printing X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=855fe51e1854e196bdd04a92f1be34f2127d058a;p=users%2Fjedix%2Flinux-maple.git mm/show_mem: dump the status of the mem alloc profiling before printing This patchset fixes two issues we saw in production rollout. The first issue is that we saw all zero output of memory allocation profiling information from show_mem() if CONFIG_MEM_ALLOC_PROFILING is set and sysctl.vm.mem_profiling=0. This cause ambiguity as we don't know what 0B actually means in the output. It can mean either memory allocation profiling is temporary disabled or the allocation at that position is actually 0. Such ambiguity will make further parsing harder as we cannot differentiate between two case. The second issue is that multiple entities can call show_mem() which messed up the allocation info in dmesg. We saw outputs like this: 327 MiB 83635 mm/compaction.c:1880 func:compaction_alloc 48.4 GiB 12684937 mm/memory.c:1061 func:folio_prealloc 7.48 GiB 10899 mm/huge_memory.c:1159 func:vma_alloc_anon_folio_pmd 298 MiB 95216 kernel/fork.c:318 func:alloc_thread_stack_node 250 MiB 63901 mm/zsmalloc.c:987 func:alloc_zspage 1.42 GiB 372527 mm/memory.c:1063 func:folio_prealloc 1.17 GiB 95693 mm/slub.c:2424 func:alloc_slab_page 651 MiB 166732 mm/readahead.c:270 func:page_cache_ra_unbounded 419 MiB 107261 net/core/page_pool.c:572 func:__page_pool_alloc_pages_slow 404 MiB 103425 arch/x86/mm/pgtable.c:25 func:pte_alloc_one The above example is because one kthread invokes show_mem() from __alloc_pages_slowpath while kernel itself calls oom_kill_process() This patch (of 2): This patch prints the status of the memory allocation profiling before __show_mem actually prints the detailed allocation info. This way will let us know the `0B` we saw in allocation info is because the profiling is disabled or the allocation is actually 0B. Link: https://lkml.kernel.org/r/cover.1756897825.git.pyyjason@gmail.com Link: https://lkml.kernel.org/r/d7998ea0ddc2ea1a78bb6e89adf530526f76679a.1756897825.git.pyyjason@gmail.com Signed-off-by: Yueyang Pan Acked-by: Usama Arif Acked-by: Vlastimil Babka Acked-by: Zi Yan Acked-by: Suren Baghdasaryan Reviewed-by: Vishal Moola (Oracle) Acked-by: Shakeel Butt Cc: Brendan Jackman Cc: Johannes Weiner Cc: Michal Hocko Signed-off-by: Andrew Morton --- diff --git a/mm/show_mem.c b/mm/show_mem.c index c563d9adfa87..22bb8b045671 100644 --- a/mm/show_mem.c +++ b/mm/show_mem.c @@ -431,7 +431,8 @@ void __show_mem(unsigned int filter, nodemask_t *nodemask, int max_zone_idx) nr = alloc_tag_top_users(tags, ARRAY_SIZE(tags), false); if (nr) { - pr_notice("Memory allocations:\n"); + pr_notice("Memory allocations (profiling is currently turned %s):\n", + mem_alloc_profiling_enabled() ? "on" : "off"); for (i = 0; i < nr; i++) { struct codetag *ct = tags[i].ct; struct alloc_tag *tag = ct_to_alloc_tag(ct);