From: Steven Rostedt <rostedt@goodmis.org>
To: David Laight <David.Laight@ACULAB.COM>
Cc: 'linux-kernel' <linux-kernel@vger.kernel.org>
Subject: Re: sched/fair: Long delays starting RT processes on idle cpu.
Date: Mon, 27 Jan 2020 10:49:48 -0500 [thread overview]
Message-ID: <20200127104948.59eac75a@gandalf.local.home> (raw)
In-Reply-To: <13797bbe87b64f34877b89a5bbdb6d03@AcuMS.aculab.com>
On Mon, 27 Jan 2020 15:39:24 +0000
David Laight <David.Laight@ACULAB.COM> wrote:
> I'd have thought that the processor should wake up much faster than that.
> I can't see the memory write that is paired with the monitor/mwait.
> Does it need a strong barrier?
You may want to prevent the CPU from going into a deep C state. 90us is
something I would expect if the CPU is in a deep C state (I've seen
much longer wake up times due to deep C state).
Boot the kernel with idle=poll and see if you can trigger the same
latency. If not, then you know it's the CPU going into a deep C state
that is causing your latency.
-- Steve
next prev parent reply other threads:[~2020-01-27 15:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-27 15:39 sched/fair: Long delays starting RT processes on idle cpu David Laight
2020-01-27 15:49 ` Steven Rostedt [this message]
2020-01-27 16:56 ` David Laight
2020-01-27 17:15 ` Steven Rostedt
2020-01-28 11:45 ` David Laight
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