linux-kernel - Re: [PATCH v3] perf cpumap: Reduce cpu size from int to int16

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 for Android: free password hash cracker in your pocket

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

Message-Id: <174067502823.1401960.12891801652873612376.b4-ty@kernel.org>
Date: Thu, 27 Feb 2025 08:50:28 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
 Arnaldo Carvalho de Melo <acme@...nel.org>, 
 Mark Rutland <mark.rutland@....com>, 
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
 Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>, 
 Kan Liang <kan.liang@...ux.intel.com>, James Clark <james.clark@...aro.org>, 
 Tim Chen <tim.c.chen@...ux.intel.com>, 
 Yicong Yang <yangyicong@...ilicon.com>, 
 Ravi Bangoria <ravi.bangoria@....com>, linux-perf-users@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Kyle Meyer <kyle.meyer@....com>, 
 Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCH v3] perf cpumap: Reduce cpu size from int to int16_t

On Mon, 10 Feb 2025 11:12:31 -0800, Ian Rogers wrote:
> Fewer than 32k logical CPUs are currently supported by perf. A cpumap
> is indexed by an integer (see perf_cpu_map__cpu) yielding a perf_cpu
> that wraps a 4-byte int for the logical CPU - the wrapping is done
> deliberately to avoid confusing a logical CPU with an index into a
> cpumap. Using a 4-byte int within the perf_cpu is larger than required
> so this patch reduces it to the 2-byte int16_t. For a cpumap
> containing 16 entries this will reduce the array size from 64 to 32
> bytes. For very large servers with lots of logical CPUs the size
> savings will be greater.
> 
> [...]
Applied to perf-tools-next, thanks!

Best regards,
Namhyung