linux-kernel - [PATCH v1 0/2] mm/show_mem: Bug fix for print mem alloc info

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Message-ID: <cover.1756318426.git.pyyjason@gmail.com>
Date: Wed, 27 Aug 2025 11:34:21 -0700
From: Yueyang Pan <pyyjason@...il.com>
To: Suren Baghdasaryan <surenb@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Michal Hocko <mhocko@...e.com>,
	Brendan Jackman <jackmanb@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Zi Yan <ziy@...dia.com>,
	Usama Arif <usamaarif642@...il.com>
Cc: linux-mm@...ck.org,
	kernel-team@...a.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH v1 0/2] mm/show_mem: Bug fix for print mem alloc info

This patch set 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. In this case, the behaviour 
should be the same as when CONFIG_MEM_ALLOC_PROFILING is unset, 
where show_mem prints nothing about the information. This will make 
further parse easier as we don't have to differentiate what a all 
zero line actually means (Does it mean  0 bytes are allocated 
or simply memory allocation profiling is disabled).

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()

Yueyang Pan (2):
  mm/show_mem: No print when not mem_alloc_profiling_enabled()
  mm/show_mem: Add trylock while printing alloc info

 mm/show_mem.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

-- 
2.47.3