From: Mike Galbraith <efault@gmx.de>
To: Chen Yu <yu.c.chen@intel.com>, kprateek.nayak@amd.com
Cc: Aishwarya Rambhadran <aishwarya.rambhadran@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
mingo@kernel.org, longman@redhat.com,
chenridong@huaweicloud.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
vschneid@redhat.com, tj@kernel.org, hannes@cmpxchg.org,
mkoutny@suse.com, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, jstultz@google.com,
qyousef@layalina.io, Ryan Roberts <ryan.roberts@arm.com>,
chen.yu@linux.dev
Subject: Re: [REGRESSION] [PATCH v3 7/7] sched/eevdf: Move to a single runqueue
Date: Mon, 28 Sep 2026 15:00:04 +0200 [thread overview]
Message-ID: <4d4f5fdee4d1f462ba3490a6b3921006285e7fcc.camel@gmx.de> (raw)
In-Reply-To: <arnbKNWNIIEcQ0a-@chenyu-dev>
On Mon, 2026-09-28 at 11:12 +0800, Chen Yu wrote:
>
> According to my test last week, stacking the waker and wakee on the same CPU brings
> a big improvement on my machine, iff the memory bandwidth is saturated. By comparison,
> if the memory bandwidth is low, stacking the wakee on top of the waker causes harm.
Ditto CPU wise. The impact of even modest waker/wakee concurrency is
considerable. For much of netperf, the post-wakeup tail becomes a CPU
service latency injection for the wakee when unnecessarily stacked.
While cache misses sting, those hurt.
As box approaches saturation, stacking of somewhat synchronous stuff
becomes a better bet. Aiming for having only waker's tail between
wakee and CPU has decent chance of being a winner in a box full of
wider obstacles.
-Mike
next prev parent reply other threads:[~2026-09-28 13:00 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-05 12:40 [PATCH v3 0/7] sched: Flatten the pick Peter Zijlstra
2026-06-05 12:40 ` [PATCH v3 1/7] sched/fair: Add cgroup_mode switch Peter Zijlstra
2026-06-30 9:03 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2026-06-05 12:40 ` [PATCH v3 2/7] sched/fair: Add cgroup_mode: up Peter Zijlstra
2026-06-05 15:07 ` Peter Zijlstra
2026-06-30 9:03 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2026-06-05 12:40 ` [PATCH v3 3/7] sched/fair: Add cgroup_mode: max Peter Zijlstra
2026-06-10 15:09 ` Waiman Long
2026-06-10 15:42 ` Waiman Long
2026-06-11 13:49 ` Peter Zijlstra
2026-06-11 13:47 ` Peter Zijlstra
2026-06-11 20:57 ` Waiman Long
2026-06-30 9:03 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2026-06-05 12:40 ` [PATCH v3 4/7] sched/fair: Add cgroup_mode: concur Peter Zijlstra
2026-06-30 9:03 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2026-06-05 12:40 ` [PATCH v3 5/7] sched/fair: Add cgroup_mode: tasks Peter Zijlstra
2026-06-30 9:03 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2026-06-05 12:40 ` [PATCH v3 6/7] sched/fair: Change the default cgroup_mode to concur Peter Zijlstra
2026-06-30 9:03 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2026-06-05 12:40 ` [PATCH v3 7/7] sched/eevdf: Move to a single runqueue Peter Zijlstra
2026-06-20 3:54 ` Chen, Yu C
2026-06-26 11:40 ` Peter Zijlstra
2026-06-29 14:02 ` Vincent Guittot
2026-06-30 9:03 ` [tip: sched/core] sched/fair: Fix overflow in update_tg_cfs_runnable() tip-bot2 for Chen, Yu C
2026-06-30 9:03 ` [tip: sched/core] sched/eevdf: Move to a single runqueue tip-bot2 for Peter Zijlstra (Intel)
2026-09-23 14:21 ` [REGRESSION] [PATCH v3 7/7] " Aishwarya Rambhadran
2026-09-23 16:48 ` Chen Yu
2026-09-24 7:05 ` K Prateek Nayak
2026-09-24 8:19 ` Mike Galbraith
2026-09-28 3:12 ` Chen Yu
2026-09-28 13:00 ` Mike Galbraith [this message]
2026-06-09 5:37 ` [PATCH v3 0/7] sched: Flatten the pick K Prateek Nayak
2026-06-12 2:29 ` Shubhang Kaushik
2026-08-17 16:05 ` Szabina Korbai
2026-08-17 16:35 ` K Prateek Nayak
2026-08-18 9:04 ` Szabina Korbai
2026-08-18 9:16 ` Peter Zijlstra
2026-08-21 10:37 ` Szabina Korbai
2026-08-24 14:51 ` Chen Yu
2026-08-24 13:53 ` Peter Zijlstra
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