linux-kernel - Re: [PATCH 4/5] Create rebalance_domains from rebalance

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Date:	Thu, 26 Oct 2006 09:19:29 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
cc:	akpm@...l.org, Peter Williams <pwil3058@...pond.net.au>,
	linux-kernel@...r.kernel.org,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	Dave Chinner <dgc@....com>, Ingo Molnar <mingo@...e.hu>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 4/5] Create rebalance_domains from rebalance_tick

On Thu, 26 Oct 2006, Nick Piggin wrote:

> > While we are at it: Take the opportunity to avoid taking
> > the request queue lock in wake_priority_sleeper if
> > there are no running processes.
> 
> Can you split this out? It is good without the tasklet based
> rebalancing.

Sure next rollup will have this:


Avoid taking the rq lock in wake_priority sleeper

Avoid taking the request queue lock in wake_priority_sleeper if
there are no running processes.

Signed-off-by: Christoph Lameter <clameter@....com>

Index: linux-2.6.19-rc3/kernel/sched.c
===================================================================
--- linux-2.6.19-rc3.orig/kernel/sched.c	2006-10-26 11:13:29.000000000 -0500
+++ linux-2.6.19-rc3/kernel/sched.c	2006-10-26 11:16:44.896476659 -0500
@@ -2900,6 +2900,9 @@ static inline int wake_priority_sleeper(
 	int ret = 0;
 
 #ifdef CONFIG_SCHED_SMT
+	if (!rq->nr_running)
+		return 0;
+
 	spin_lock(&rq->lock);
 	/*
 	 * If an SMT sibling task has been put to sleep for priority
-
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