From: Martin Wilck <martin.wilck@suse.com>
To: Benjamin Marzinski <bmarzins@redhat.com>
Cc: Christophe Varoqui <christophe.varoqui@opensvc.com>,
device-mapper development <dm-devel@lists.linux.dev>
Subject: Re: [PATCH] multipathd: make multipathd set priority to RLIMIT_RTPRIO
Date: Tue, 09 Apr 2024 20:45:16 +0200 [thread overview]
Message-ID: <bb17d09ef40d74489d1f8219355f559409f5ecbe.camel@suse.com> (raw)
In-Reply-To: <ZhVo9uHMm3-F1MIe@bmarzins-01.fast.eng.rdu2.dc.redhat.com>
On Tue, 2024-04-09 at 12:12 -0400, Benjamin Marzinski wrote:
> On Tue, Apr 09, 2024 at 04:38:57PM +0200, Martin Wilck wrote:
> > On Fri, 2024-03-29 at 14:28 -0400, Benjamin Marzinski wrote:
> > > With this change, if the SCHED_RT_PRIO compiler flag is not set,
> > > multipathd will call getrlimit(RLIMIT_RTPRIO, ...) and look at
> > > the
> > > hard
> > > limit. It it's 0, multipath will do nothing. Otherwise it will
> > > change
> > > its scheduling policy to SCHED_RR and its priority to the hard
> > > limit.
> > >
> > > This allows users to change the priority of that multipathd runs
> > > with
> > > by
> > > adding
> > >
> > > LimitRTPRIO=<prio>
> > >
> > > to the [Service] section of the multipathd.service unit file.
> > > Setting
> > > LimitRTPRIO=0 will make multipathd run as a normal process, while
> > > setting LimitRTPRIO=infinity will make it use the maximum
> > > SCHED_RR
> > > prio,
> > > which is 99.
> > >
> > > Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
> >
> > This looks good to me, but do we really need both the RLIMIT_RTPRIO
> > and
> > the SCHED_RT_PRIO mechanism?
>
> Not if https://github.com/dracutdevs/dracut/pull/2563 ever gets
> merged,
> we don't.
Unfortunately that PR has caused some regressions in the dracut CI
which I haven't had time to analyze / fix yet.
> Until then it seemed easier to keep a knob to let us control
> this ourselves, rather than try to sync with a change in dracut.
>
> Obviously, I'm still not convinced that it really matters whether or
> not
> multipathd is running with SCHED_RR, so we probably could just say
> that
> until dracut gets updated, we just don't run in SCHED_RR in the
> initramfs. I'm fine with pulling the compiler flag if you want.
I would prefer to have just one way to configure this, unless we have
really strong reasons to support both.
Thanks,
Martin
prev parent reply other threads:[~2024-04-09 18:45 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-29 18:28 [PATCH] multipathd: make multipathd set priority to RLIMIT_RTPRIO Benjamin Marzinski
2024-04-09 14:38 ` Martin Wilck
2024-04-09 16:12 ` Benjamin Marzinski
2024-04-09 18:45 ` Martin Wilck [this message]
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