From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Waiman Long <longman@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
linux-mm@kvack.org, Thomas Gleixner <tglx@linutronix.de>
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@redhat.com>
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 19:49 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
2021-12-15 4:36 ` Davidlohr Bueso
2021-12-15 16:58 ` Waiman Long
2021-12-17 11:42 ` Sebastian Andrzej Siewior
2021-12-17 18:21 ` Sebastian Andrzej Siewior
2021-12-17 18:46 ` Waiman Long
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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