linux-kernel - Re: [PATCH v2 1/1] alloc_tag: mark inaccurate allocation counters in /proc/allocinfo output

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250915171112.f71a7606a7f9fd3054662bed@linux-foundation.org>
Date: Mon, 15 Sep 2025 17:11:12 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: kent.overstreet@...ux.dev, vbabka@...e.cz, hannes@...xchg.org,
 usamaarif642@...il.com, rientjes@...gle.com, roman.gushchin@...ux.dev,
 harry.yoo@...cle.com, shakeel.butt@...ux.dev, 00107082@....com,
 pyyjason@...il.com, pasha.tatashin@...een.com, souravpanda@...gle.com,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] alloc_tag: mark inaccurate allocation counters
 in /proc/allocinfo output

On Mon, 15 Sep 2025 16:02:24 -0700 Suren Baghdasaryan <surenb@...gle.com> wrote:

> While rare, memory allocation profiling can contain inaccurate counters
> if slab object extension vector allocation fails. That allocation might
> succeed later but prior to that, slab allocations that would have used
> that object extension vector will not be accounted for. To indicate
> incorrect counters, "accurate:no" marker is appended to the call site
> line in the /proc/allocinfo output.
> Bump up /proc/allocinfo version to reflect the change in the file format
> and update documentation.
> 
> Example output with invalid counters:
> allocinfo - version: 2.0
>            0        0 arch/x86/kernel/kdebugfs.c:105 func:create_setup_data_nodes
>            0        0 arch/x86/kernel/alternative.c:2090 func:alternatives_smp_module_add
>            0        0 arch/x86/kernel/alternative.c:127 func:__its_alloc accurate:no
>            0        0 arch/x86/kernel/fpu/regset.c:160 func:xstateregs_set
>            0        0 arch/x86/kernel/fpu/xstate.c:1590 func:fpstate_realloc
>            0        0 arch/x86/kernel/cpu/aperfmperf.c:379 func:arch_enable_hybrid_capacity_scale
>            0        0 arch/x86/kernel/cpu/amd_cache_disable.c:258 func:init_amd_l3_attrs
>        49152       48 arch/x86/kernel/cpu/mce/core.c:2709 func:mce_device_create accurate:no
>        32768        1 arch/x86/kernel/cpu/mce/genpool.c:132 func:mce_gen_pool_create
>            0        0 arch/x86/kernel/cpu/mce/amd.c:1341 func:mce_threshold_create_device
> 
> ...
>
> --- a/Documentation/filesystems/proc.rst
> +++ b/Documentation/filesystems/proc.rst
> @@ -1009,6 +1009,10 @@ number, module (if originates from a loadable module) and the function calling
>  the allocation. The number of bytes allocated and number of calls at each
>  location are reported. The first line indicates the version of the file, the
>  second line is the header listing fields in the file.
> +If file version is 2.0 or higher then each line may contain additional
> +<key>:<value> pairs representing extra information about the call site.
> +For example if the counters are not accurate, the line will be appended with
> +"accurate:no" pair.

Perhaps we can tell people what accurate:no actually means.  It is a
rather disturbing thing to see!  How worried should our users be about
it?