From: Christoph Lameter Date: Tue, 19 Jun 2007 19:39:03 +0000 (+0200) Subject: [PATCH] sched: fix next_interval determination in idle_balance() X-Git-Tag: v2.6.20.16~9 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=103f048b6f30360d3251c670b0a6714282ceb2c6;p=thirdparty%2Fkernel%2Fstable.git [PATCH] sched: fix next_interval determination in idle_balance() Fix massive SMP imbalance on NUMA nodes observed on 2.6.21.5 with CFS. (and later on reproduced without CFS as well). 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 and nodes might stay idle for very long times. Siddha also spotted that the conversion of the balance interval to jiffies is missing. Fix that to. From: Srivatsa Vaddagiri also continue the loop if !(sd->flags & SD_LOAD_BALANCE). Tested-by: Paul E. McKenney 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 Signed-off-by: Ingo Molnar Signed-off-by: Chris Wright Signed-off-by: Greg Kroah-Hartman --- diff --git a/kernel/sched.c b/kernel/sched.c index 62db30c73554d..907ab056c71b8 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2814,17 +2814,21 @@ 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; - if (pulled_task) - break; - } + this_rq, sd); + + 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) /*