linux-kernel - RE: [PATCH] tools/power turbostat: Increase the limit for fd opened

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Message-ID: <001601d9f2ea$26ef3420$74cd9c60$@telus.net>
Date:   Fri, 29 Sep 2023 08:32:26 -0700
From:   "Doug Smythies" <dsmythies@...us.net>
To:     "'Wyes Karny'" <wyes.karny@....com>
Cc:     <lenb@...nel.org>, <linux-pm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] tools/power turbostat: Increase the limit for fd opened

Hi Wyes,

On 2023.09.26 10:16 Wyes Karny wrote:
> On 22 Sep 13:48, Doug Smythies wrote:
> > On 2023.09.22 02:28 Wyes Karny wrote:
> >
> > > When running turbostat, a system with 512 cpus reaches the limit for
> >
> > Suggest" ... reaches the default limit for..."
> >
> > > maximum number of file descriptors that can be opened. To solve this
> > > problem, the limit is raised to 2^15, which is a large enough number.
> > >
> > > Below data is collected from AMD server systems while running turbostat:
> > >
> > > |-----------+-------------------------------|
> > > | # of cpus | # of opened fds for turbostat |
> > > |-----------+-------------------------------|
> > > | 128       | 260                           |
> > > |-----------+-------------------------------|
> > > | 192       | 388                           |
> > > |-----------+-------------------------------|
> > > | 512       | 1028                          |
> > > |-----------+-------------------------------|
> >
> > The number of open files is a function of what is being "show"ed or "hide"en.
> > They can also increase beyond the above 2 X (# of CPUs) + 4 number
> > via the --add directive.
> > >
> > > So, the new max limit would be sufficient up to 2^14 cpus.
> >
> > Well, not quiet, but the point is valid.
> >
> > Normally, I would assume that a server with a large number of
> > CPUs would have set a much higher limit of the number of open
> > files than the default. I use 131,072 and so this patch reduces the
> > maximum.
>
> I think below will fix the problem.
>
> +#define MAX_NOFILE 0x8000
> +
> +void set_rlimit(void)
> +{
> +       struct rlimit limit;
> +
> +       if(getrlimit(RLIMIT_NOFILE, &limit) < 0) {
> +               err(1, "Failed to get rlimit");
> +       }
> +
> +       if (limit.rlim_max < MAX_NOFILE)
> +               limit.rlim_max = MAX_NOFILE;
> +       if (limit.rlim_cur < MAX_NOFILE)
> +               limit.rlim_cur = MAX_NOFILE;
> +
> +       if (setrlimit(RLIMIT_NOFILE, &limit) < 0) {
> +               err(1, "Failed to set rlimit");
> +       }
> +       return;
> +}
>
> Is this looks okay to you?

Either the original or the above is fine.
I was just being nit-picky and annoying is all.
I still added a "Reviewed-by" below.

... Doug

> Thanks,
> Wyes
> >
> > Unpatched:
> > root@s19:~# cat /proc/47043/limits | grep "Max open files"
> > Max open files            131072               131072               files
> >
> > Patched:
> > root@s19:~# cat /proc/47032/limits | grep "Max open files"
> > Max open files            32768                32768                files
> >
> > Anyway:
> >
> > Reviewed-by: Doug Smythies <dsmythies@...us.net>
> > Tested-by: Doug Smythies <dsmythies@...us.net>
> >
> > >
> > > Signed-off-by: Wyes Karny <wyes.karny@....com>
> > > ---
> > >  tools/power/x86/turbostat/turbostat.c | 15 +++++++++++++++
> > >  1 file changed, 15 insertions(+)
> > >
> > > diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
> > > index 9a10512e3407..23f1fe58289a 100644
> > > --- a/tools/power/x86/turbostat/turbostat.c
> > > +++ b/tools/power/x86/turbostat/turbostat.c
> > > @@ -6717,6 +6717,18 @@ void cmdline(int argc, char **argv)
> > >       }
> > >  }
> > >
> > > +void set_rlimit(void)
> > > +{
> > > +     struct rlimit limit;
> > > +
> > > +     limit.rlim_cur = 0x8000;
> > > +     limit.rlim_max = 0x8000;
> > > +
> > > +     if (setrlimit(RLIMIT_NOFILE, &limit) < 0) {
> > > +             err(1, "Failed to set rlimit");
> > > +     }
> > > +}
> > > +
> > >  int main(int argc, char **argv)
> > >  {
> > >       outf = stderr;
> > > @@ -6729,6 +6741,9 @@ int main(int argc, char **argv)
> > >
> > >       probe_sysfs();
> > >
> > > +     if (!getuid())
> > > +             set_rlimit();
> > > +
> > >       turbostat_init();
> > >
> > >       msr_sum_record();
> > > --
> > > 2.34.1