linux-kernel - Re: [PATCH v3] perf stat: Add/fix bperf cgroup max events workarounds

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Message-Id: <176158935550.1688092.6810694230290351513.b4-ty@kernel.org>
Date: Mon, 27 Oct 2025 11:22:35 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
 Arnaldo Carvalho de Melo <acme@...nel.org>, 
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
 Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>, 
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCH v3] perf stat: Add/fix bperf cgroup max events
 workarounds

On Sat, 25 Oct 2025 13:28:34 -0700, Ian Rogers wrote:
> Commit b8308511f6e0 bumped the max events to 1024 but this results in
> BPF verifier issues if the number of command line events is too
> large. Workaround this by:
> 
> 1) moving the constants to a header file to share between BPF and perf
>    C code,
> 2) testing that the maximum number of events doesn't cause BPF
>    verifier issues in debug builds,
> 3) lower the max events from 1024 to 128,
> 4) in perf stat, if there are more events than the BPF counters can
>    support then disable BPF counter usage.
> 
> [...]
Applied to perf-tools-next, thanks!

Best regards,
Namhyung