From: Sebastian Andrzej Siewior <bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
To: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Vladimir Davydov
<vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
Subject: Re: [PATCH-next v3] mm/memcg: Properly handle memcg_stock access for PREEMPT_RT
Date: Fri, 17 Dec 2021 20:48:47 +0100 [thread overview]
Message-ID: <Ybzpn59+ecDCnULt@linutronix.de> (raw)
In-Reply-To: <b82efbad-1eb2-9441-ab0b-cbb3d2b5eac6-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
On 2021-12-17 13:46:53 [-0500], Waiman Long wrote:
> > annotation. Looking at the history, I'm also impressed by that fact that
> > disabling/ enabling interrupts is *so* expensive that all this is
> > actually worth it.
>
> For !RT with voluntary or no preemption, preempt_disable() is just a
> compiler barrier. So it is definitely cheaper than disabling interrupt. The
> performance benefit is less with preemptible but !RT kernel. Microbenchmark
> testing shows a performance improvement of a few percents depending on the
> exact benchmark.
Thanks for confirming. I got the feeling that this optimisation is for
!CONFIG_PREEMPTION. So I instead of depending on CONFIG_PREEMPT_RT I'm
leaning towards CONFIG_PREEMPT instead.
> Cheers,
> Longman
Sebastian
next prev parent reply other threads:[~2021-12-17 19:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-14 14:44 [PATCH-next v3] mm/memcg: Properly handle memcg_stock access for PREEMPT_RT Waiman Long
[not found] ` <20211214144412.447035-1-longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2021-12-15 4:36 ` Davidlohr Bueso
2021-12-15 16:58 ` Waiman Long
2021-12-17 11:42 ` Sebastian Andrzej Siewior
[not found] ` <Ybx3ubNFfGpCqhn0-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2021-12-17 18:21 ` Sebastian Andrzej Siewior
2021-12-17 18:46 ` Waiman Long
[not found] ` <b82efbad-1eb2-9441-ab0b-cbb3d2b5eac6-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2021-12-17 19:48 ` Sebastian Andrzej Siewior [this message]
2021-12-19 13:20 ` [mm/memcg] 3928ba024a: WARNING:possible_recursive_locking_detected kernel test robot
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