linux-kernel - Re: [PATCH v3] perf bench sched pipe: Add -G/--cgroups option

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Message-ID: <ZS1ajf/9HmgUyyCl@kernel.org>
Date:   Mon, 16 Oct 2023 12:45:17 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v3] perf bench sched pipe: Add -G/--cgroups option

Em Mon, Oct 16, 2023 at 12:38:12PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Oct 16, 2023 at 11:35:35AM +0200, Ingo Molnar escreveu:
> > 
> > 
> > * Namhyung Kim <namhyung@...nel.org> wrote:
> > 
> > > +	/* try cgroup v2 interface first */
> > > +	if (threaded)
> > > +		fd = openat(cgrp->fd, "cgroup.threads", O_WRONLY);
> > > +	else
> > > +		fd = openat(cgrp->fd, "cgroup.procs", O_WRONLY);
> > > +
> > > +	/* try cgroup v1 if failed */
> > > +	if (fd < 0)
> > > +		fd = openat(cgrp->fd, "tasks", O_WRONLY);
> > > +
> > > +	if (fd < 0) {
> > > +		char mnt[PATH_MAX];
> > > +
> > > +		printf("Failed to open cgroup file in %s\n", cgrp->name);
> > > +
> > > +		if (cgroupfs_find_mountpoint(mnt, sizeof(mnt), "perf_event") == 0)
> > > +			printf(" Hint: create the cgroup first, like 'mkdir %s/%s'\n",
> > > +			       mnt, cgrp->name);
> > 
> > Ok, this works too I suppose.
> > 
> > Acked-by: Ingo Molnar <mingo@...nel.org>
> 
> I'm not getting that:
> 
> [root@...e ~]# perf bench sched pipe -l 10000 -G AAA,BBB
> # Running 'sched/pipe' benchmark:
> no access to cgroup /sys/fs/cgroup/AAA
> cannot open sender cgroup: AAA
>  Usage: perf bench sched pipe <options>
> 
>     -G, --cgroups <SEND,RECV>
>                           Put sender and receivers in given cgroups
> [root@...e ~]#
> 
> Its better now as it bails out, but it is not emitting any message that
> helps with running the test, well, there is that /sys/fs/cgroup/AAA
> path, lemme try doing a mkdir:
> 
> [root@...e ~]# perf bench sched pipe -l 10000 -G AAA,BBB
> # Running 'sched/pipe' benchmark:
> no access to cgroup /sys/fs/cgroup/BBB
> cannot open receiver cgroup: BBB
>  Usage: perf bench sched pipe <options>
> 
>     -G, --cgroups <SEND,RECV>
>                           Put sender and receivers in given cgroups
> [root@...e ~]#
> 
> [root@...e ~]# perf bench sched pipe -l 10000 -G AAA,BBB
> # Running 'sched/pipe' benchmark:
> [root@...e ~]#
> 
> It seems to be bailing out but doesn't run the test nor emits any
> warning.

(gdb) run bench sched pipe -l 10000
Starting program: /root/bin/perf bench sched pipe -l 10000
# Running 'sched/pipe' benchmark:
[Detaching after fork from child process 33618]

Breakpoint 1, bench_sched_pipe (argc=0, argv=0x7fffffffe3d8) at bench/sched-pipe.c:259
259		if (threads[0].cgroup_failed || threads[1].cgroup_failed)
(gdb) p threads[0].cgroup_failed
$1 = 137
(gdb) p threads[1].cgroup_failed
$2 = false
(gdb) n
260			return 0;
(gdb)

But I'm not even using cgroups?

- Arnaldo