linux-kernel - Re: [PATCH] perf report: Do not process non-JIT BPF ksymbol events

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Message-Id: <174137099810.213280.18383915542896888005.b4-ty@kernel.org>
Date: Fri, 07 Mar 2025 10:09:58 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>, 
 Ian Rogers <irogers@...gle.com>, Kan Liang <kan.liang@...ux.intel.com>, 
 Namhyung Kim <namhyung@...nel.org>
Cc: Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>, 
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, 
 LKML <linux-kernel@...r.kernel.org>, linux-perf-users@...r.kernel.org, 
 bpf@...r.kernel.org, Kevin Nomura <nomurak@...gle.com>, 
 Song Liu <song@...nel.org>
Subject: Re: [PATCH] perf report: Do not process non-JIT BPF ksymbol events

On Wed, 05 Mar 2025 15:28:38 -0800, Namhyung Kim wrote:
> The length of PERF_RECORD_KSYMBOL for BPF is a size of JITed code so
> it'd be 0 when it's not JITed.  The ksymbol is needed to symbolize the
> code when it gets samples in the region but non-JITed code cannot get
> samples.  Thus it'd be ok to ignore them.
> 
> Actually it caused a performance issue in the perf tools on old ARM
> kernels where it can refuse to JIT some BPF codes.  It ended up
> splitting the existing kernel map (kallsyms).  And later lookup for a
> kernel symbol would create a new kernel map from kallsyms and then
> split it again and again. :(
> 
> [...]
Applied to perf-tools-next, thanks!

Best regards,
Namhyung