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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 :-)

  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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