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[PATCH] sched: less newidle locking 

Similarly to the earlier change in load_balance, only lock the runqueue in
load_balance_newidle if the busiest queue found has a nr_running > 1.  This
will reduce frequency of expensive remote runqueue lock aquisitions in the
schedule() path on some workloads.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Nick Piggin 2005-09-10 00:26:16 -07:00 committed by Linus Torvalds
parent 67f9a619e7
commit d6d5cfaf45
1 changed files with 10 additions and 7 deletions
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17
kernel/sched.c
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@ -2104,8 +2104,7 @@ static int load_balance(int this_cpu, runqueue_t *this_rq,
*/
double_lock_balance(this_rq, busiest);
nr_moved = move_tasks(this_rq, this_cpu, busiest,
imbalance, sd, idle,
&all_pinned);
imbalance, sd, idle, &all_pinned);
spin_unlock(&busiest->lock);
/* All tasks on this runqueue were pinned by CPU affinity */
@ -2200,18 +2199,22 @@ static int load_balance_newidle(int this_cpu, runqueue_t *this_rq,
BUG_ON(busiest == this_rq);
/* Attempt to move tasks */
double_lock_balance(this_rq, busiest);
schedstat_add(sd, lb_imbalance[NEWLY_IDLE], imbalance);
nr_moved = move_tasks(this_rq, this_cpu, busiest,
nr_moved = 0;
if (busiest->nr_running > 1) {
/* Attempt to move tasks */
double_lock_balance(this_rq, busiest);
nr_moved = move_tasks(this_rq, this_cpu, busiest,
imbalance, sd, NEWLY_IDLE, NULL);
spin_unlock(&busiest->lock);
}
if (!nr_moved)
schedstat_inc(sd, lb_failed[NEWLY_IDLE]);
else
sd->nr_balance_failed = 0;
spin_unlock(&busiest->lock);
return nr_moved;
out_balanced: