linux-kernel - Re: + sched-use-tasklet-to-call-balancing.patch added to -mm tree

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Message-ID: <Pine.LNX.4.64.0611071113390.4582@schroedinger.engr.sgi.com>
Date:	Tue, 7 Nov 2006 11:17:07 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
cc:	Ingo Molnar <mingo@...e.hu>, akpm@...l.org,
	mm-commits@...r.kernel.org, nickpiggin@...oo.com.au,
	linux-kernel@...r.kernel.org
Subject: Re: + sched-use-tasklet-to-call-balancing.patch added to -mm tree

Tasklets are scheduled on the same cpu that triggered the tasklet. They 
are just moved to other processors if the processor goes down. So that 
aspect is fine. We just need a tasklet struct per cpu.



User a per cpu tasklet to schedule rebalancing

Turns out that tasklets have a flag that only allows one instance to run
on all processors. So we need a tasklet structure for each processor.

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

Index: linux-2.6.19-rc4-mm2/kernel/sched.c
===================================================================
--- linux-2.6.19-rc4-mm2.orig/kernel/sched.c	2006-11-06 13:58:38.000000000 -0600
+++ linux-2.6.19-rc4-mm2/kernel/sched.c	2006-11-07 13:05:56.236343144 -0600
@@ -2918,7 +2918,8 @@ static void rebalance_domains(unsigned l
 	this_rq->next_balance = next_balance;
 }
 
-DECLARE_TASKLET(rebalance, &rebalance_domains, 0L);
+static DEFINE_PER_CPU(struct tasklet_struct, rebalance) =
+		{ NULL, 0, ATOMIC_INIT(0), rebalance_domains, 0L };
 #else
 /*
  * on UP we do not need to balance between CPUs:
@@ -3171,7 +3172,7 @@ void scheduler_tick(void)
 #ifdef CONFIG_SMP
 	update_load(rq);
 	if (time_after_eq(jiffies, rq->next_balance))
-		tasklet_schedule(&rebalance);
+		tasklet_schedule(&__get_cpu_var(rebalance));
 #endif
 }
 

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