From: David Laight <david.laight.linux@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Yafang Shao <laoar.shao@gmail.com>,
mingo@redhat.com, will@kernel.org, boqun@kernel.org,
longman@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org,
mark.rutland@arm.com, mathieu.desnoyers@efficios.com,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
bpf@vger.kernel.org
Subject: Re: [RFC PATCH 1/2] locking: add mutex_lock_nospin()
Date: Wed, 4 Mar 2026 09:54:15 +0000 [thread overview]
Message-ID: <20260304095415.4d5f2528@pumpkin> (raw)
In-Reply-To: <20260304090249.GN606826@noisy.programming.kicks-ass.net>
On Wed, 4 Mar 2026 10:02:49 +0100
Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Mar 04, 2026 at 03:46:49PM +0800, Yafang Shao wrote:
> > Introduce mutex_lock_nospin(), a helper that disables optimistic spinning
> > on the owner for specific heavy locks. This prevents long spinning times
> > that can lead to latency spikes for other tasks on the same runqueue.
>
> This makes no sense; spinning stops on need_resched().
>
That might still be an issue if a high priority process is spinning.
But a %sys spike doesn't imply a latency spike.
Is this using the osq_lock.c code?
That will have problems on overprovisioned VMs, it tries to find out
whether the hypervisor has switched out - but ISTR that is flawed.
In reality a spin lock shouldn't be held for long enough to cause
any kind latency issue.
So something in the code that reads the list of filter functions
needs to be done differently so that the lock isn't held for as long.
David
next prev parent reply other threads:[~2026-03-04 9:54 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-04 7:46 [RFC PATCH 0/2] disable optimistic spinning for ftrace_lock Yafang Shao
2026-03-04 7:46 ` [RFC PATCH 1/2] locking: add mutex_lock_nospin() Yafang Shao
2026-03-04 9:02 ` Peter Zijlstra
2026-03-04 9:37 ` Yafang Shao
2026-03-04 10:11 ` Peter Zijlstra
2026-03-04 11:52 ` Yafang Shao
2026-03-04 12:41 ` Peter Zijlstra
2026-03-04 14:25 ` Yafang Shao
2026-03-04 9:54 ` David Laight [this message]
2026-03-04 20:57 ` Steven Rostedt
2026-03-04 21:44 ` David Laight
2026-03-05 2:17 ` Yafang Shao
2026-03-05 2:28 ` Steven Rostedt
2026-03-05 2:33 ` Yafang Shao
2026-03-05 3:00 ` Steven Rostedt
2026-03-05 3:08 ` Yafang Shao
2026-03-05 4:30 ` Waiman Long
2026-03-05 5:40 ` Yafang Shao
2026-03-05 13:21 ` Steven Rostedt
2026-03-06 2:22 ` Yafang Shao
2026-03-06 10:00 ` David Laight
2026-03-09 2:34 ` Yafang Shao
2026-03-05 18:34 ` Waiman Long
2026-03-05 18:44 ` Waiman Long
2026-03-06 2:27 ` Yafang Shao
2026-03-05 9:32 ` David Laight
2026-03-05 19:00 ` Waiman Long
2026-03-06 2:33 ` Yafang Shao
2026-03-04 7:46 ` [RFC PATCH 2/2] ftrace: disable optimistic spinning for ftrace_lock Yafang Shao
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260304095415.4d5f2528@pumpkin \
--to=david.laight.linux@gmail.com \
--cc=boqun@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=laoar.shao@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-trace-kernel@vger.kernel.org \
--cc=longman@redhat.com \
--cc=mark.rutland@arm.com \
--cc=mathieu.desnoyers@efficios.com \
--cc=mhiramat@kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox