From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] sched: Optimize pick_next_task for idle_sched_class too
Date: Fri, 20 Jan 2017 17:52:11 +0100 [thread overview]
Message-ID: <20170120165211.GR6485@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20170120111425.5afaad5c@gandalf.local.home>
On Fri, Jan 20, 2017 at 11:14:25AM -0500, Steven Rostedt wrote:
> > OK, so I hate this patch because it makes the condition more complex,
> > and while staring at what it does for code generation I couldn't for the
> > life of me figure out why we care about prev->sched_class to begin with.
>
> I was thinking it would save on checking the rq at all, but rq is used
> by pick_next_task_*() anyway, so I doubt it's much savings.
fwiw, code generation adds something like:
CMP imm32, reg
JE imm8
So the overhead is not immense, something like 7-8 bytes, but still,
less is more :-)
next prev parent reply other threads:[~2017-01-20 16:53 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-19 15:17 [PATCH] sched: Optimize pick_next_task for idle_sched_class too Steven Rostedt
2017-01-19 17:44 ` Peter Zijlstra
2017-01-20 16:14 ` Steven Rostedt
2017-01-20 16:16 ` Steven Rostedt
2017-01-20 16:52 ` Peter Zijlstra [this message]
2017-01-30 11:54 ` [tip:sched/core] sched/core: Optimize pick_next_task() for idle_sched_class tip-bot for Peter Zijlstra
2017-02-23 10:34 ` [PATCH] sched: Optimize pick_next_task for idle_sched_class too Pavan Kondeti
2017-02-23 13:54 ` Peter Zijlstra
2017-02-23 15:15 ` Pavan Kondeti
2017-02-23 15:25 ` Peter Zijlstra
2017-02-23 16:37 ` Peter Zijlstra
2017-02-23 17:29 ` Pavan Kondeti
2017-02-23 17:45 ` Peter Zijlstra
2017-02-23 17:54 ` Peter Zijlstra
2017-02-27 17:54 ` Steven Rostedt
2017-03-01 15:53 ` Steven Rostedt
2017-03-01 16:03 ` Peter Zijlstra
2017-03-01 16:19 ` Steven Rostedt
2017-03-01 16:22 ` Peter Zijlstra
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