Re: [PATCH v2] perf symbol: Remove psw_idle() from list of idle symbols

[Ian Rogers]

On Mon, Mar 2, 2026 at 10:43 AM Arnaldo Carvalho de Melo
<acme@xxxxxxxxxx> wrote:
>
> On Mon, Feb 23, 2026 at 01:46:21PM -0800, Namhyung Kim wrote:
> > On Thu, Feb 19, 2026 at 12:38:50PM +0100, Thomas Richter wrote:
> > > Commit fa2ae4a377c0 ("s390/idle: Rewrite psw_idle() in C")
> > >
> > > removes symbols psw_idle() and psw_idle_exit() from the linux
> > > kernel for s390. Remove them in perf tool's list of idle
> > > functions. They can not be detected anymore.
> >
> > But I think old kernels may still run somewhere.  It seems the above
> > commit was merged to v6.10.  Maybe we should wait some more time before
> > removing it in the tool.
>
> Agreed, using a new perf tool, say built from the tarballs made
> available at:
>
> https://www.kernel.org/pub/linux/kernel/tools/perf/v7.0.0/perf-7.0.0-rc1.tar.xz
>
> (I will not make a rc2 available since there are no changes to the
> tools/perf codebase in this rc).
>
> On older kernels should still ignore those functions.
>
> A suggestion for work in this area instead is to get those samples into
> a special bucket, the "idle" one, and show it at some place in the
> screen.

Would it also be sensible to pass the perf_env:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/env.h?h=perf-tools-next#n74
into symbol__is_idle? The contents of the perf_env are shown by `perf
report --header`:
```
# ========
# captured on    : Mon Mar  2 11:34:47 2026
# header version : 1
# data offset    : 904
# data size      : 4268216
# feat offset    : 4269120
# hostname : google.com
# os release : 6.17.13-1rodete1-amd64
# perf version : 7.0.rc1.g982b63f6380b
# arch : x86_64
# nrcpus online : 28
# nrcpus avail : 28
# cpudesc : Intel(R) Core(TM) i7-14700
# cpuid : GenuineIntel,6,183,1
...
# e_machine : 62
#   e_flags : 0
...
```
The kernel version is in the release and the e_machine/arch captures
the CPU type.

Thanks,
Ian

> Thanks,
>
> - Arnaldo
>