Commit 92c4ca5c authored Jun 23, 2007 by Christoph Lameter Committed by Linus Torvalds Jun 24, 2007

sched: fix next_interval determination in idle_balance()



The intervals of domains that do not have SD_BALANCE_NEWIDLE must be
considered for the calculation of the time of the next balance.  Otherwise
we may defer rebalancing forever.

Siddha also spotted that the conversion of the balance interval
to jiffies is missing. Fix that to.

From: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>

also continue the loop if !(sd->flags & SD_LOAD_BALANCE).

Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

It did in fact trigger under all three of mainline, CFS, and -rt including CFS
-- see below for a couple of emails from last Friday giving results for these
three on the AMD box (where it happened) and on a single-quad NUMA-Q system
(where it did not, at least not with such severity).

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 84966343

kernel/sched.c

+13 −9

Original line number	Diff line number	Diff line
		@@ -2938,18 +2938,22 @@ static void idle_balance(int this_cpu, struct rq *this_rq)
		unsigned long next_balance = jiffies + 60 * HZ;

		for_each_domain(this_cpu, sd) {
		if (sd->flags & SD_BALANCE_NEWIDLE) {
		unsigned long interval;

		if (!(sd->flags & SD_LOAD_BALANCE))
		continue;

		if (sd->flags & SD_BALANCE_NEWIDLE)
		/* If we've pulled tasks over stop searching: */
		pulled_task = load_balance_newidle(this_cpu,
		this_rq, sd);
		if (time_after(next_balance,
		sd->last_balance + sd->balance_interval))
		next_balance = sd->last_balance
		+ sd->balance_interval;

		interval = msecs_to_jiffies(sd->balance_interval);
		if (time_after(next_balance, sd->last_balance + interval))
		next_balance = sd->last_balance + interval;
		if (pulled_task)
		break;
		}
		}
		if (!pulled_task)
		/*
		* We are going idle. next_balance may be set based on

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