linux-kernel - Re: [PATCH] perf test: Fix fails of perf stat --bpf-counters --for-each-cgroup on s390

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Message-ID: <CAM9d7cheZG+4PYf2xT0kykHW2LRt_d2GHG-mLWqvLBD3fJWFOQ@mail.gmail.com>
Date:   Mon, 11 Dec 2023 15:13:07 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Thomas Richter <tmricht@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        acme@...nel.org, svens@...ux.ibm.com, gor@...ux.ibm.com,
        sumanthk@...ux.ibm.com, hca@...ux.ibm.com
Subject: Re: [PATCH] perf test: Fix fails of perf stat --bpf-counters
 --for-each-cgroup on s390

On Fri, Dec 8, 2023 at 3:30 AM Thomas Richter <tmricht@...ux.ibm.com> wrote:
>
> On 12/8/23 12:07, Thomas Richter wrote:
> > On 12/8/23 00:26, Namhyung Kim wrote:
> >
> >> Thanks for the patch.  But I think it should support
> >> machines without systemd (or maybe with old versions).
> >>
> >> Also probably you want to reset the behavior after
> >> the test.  I think we can just run some built-in test
> >> workload like `perf test -w thloop`.
> >>
> >> Thanks,
> >> Namhyung
> >
> > Thanks for our feedback.
> > Well regarding the use of systemd daemon-reexec the manual says
> > this command restarts the systemd triggered processes.
> > There is nothing to reset. All ports stay active while the command
> > is processed.
> >
> > I tried your 'perf test -w thloop`, but that did not trigger
> > anything on system.slice.
> >
> > I do not understand enough about cgroups and system.slice, but I am
> > under the impression, that the system.slice just increment counters
> > when executed by processes under systemd control. Maybe I am wrong.

Ah, you're right.  It needs to run the task somewhere in the system.slice.
Then it'd be hard to get a proper cgroup name generally. Hmm..

My concern was it'd bind system daemons on the CPU 0 and 1 after the
test.  Probably you could run it at the end of the test again without taskset.

> >
> > The only other workload which always incremented system.slice counters
> > was 'ssh localhost ls -l', which involves local login and a running sshd.

But it won't work if the system doesn't have sshd.

Thanks,
Namhyung