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authorVincent Guittot <[email protected]>2020-06-09 14:37:48 +0200
committerPeter Zijlstra <[email protected]>2020-06-15 14:10:04 +0200
commit3ea2f097b17e13a8280f1f9386c331b326a3dbef (patch)
tree386b638bfb54cc3bcf63311ddf1915da7ee011d0
parentb4098bfc5efb1fd7ecf40165132a1283aeea3500 (diff)
sched/fair: Fix NOHZ next idle balance
With commit: 'b7031a02ec75 ("sched/fair: Add NOHZ_STATS_KICK")' rebalance_domains of the local cfs_rq happens before others idle cpus have updated nohz.next_balance and its value is overwritten. Move the update of nohz.next_balance for other idles cpus before balancing and updating the next_balance of local cfs_rq. Also, the nohz.next_balance is now updated only if all idle cpus got a chance to rebalance their domains and the idle balance has not been aborted because of new activities on the CPU. In case of need_resched, the idle load balance will be kick the next jiffie in order to address remaining ilb. Fixes: b7031a02ec75 ("sched/fair: Add NOHZ_STATS_KICK") Reported-by: Peng Liu <[email protected]> Signed-off-by: Vincent Guittot <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Reviewed-by: Valentin Schneider <[email protected]> Acked-by: Mel Gorman <[email protected]> Link: https://lkml.kernel.org/r/[email protected]
-rw-r--r--kernel/sched/fair.c23
1 files changed, 14 insertions, 9 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a785a9b262dd..295c9ffa850b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10022,7 +10022,12 @@ static void kick_ilb(unsigned int flags)
{
int ilb_cpu;
- nohz.next_balance++;
+ /*
+ * Increase nohz.next_balance only when if full ilb is triggered but
+ * not if we only update stats.
+ */
+ if (flags & NOHZ_BALANCE_KICK)
+ nohz.next_balance = jiffies+1;
ilb_cpu = find_new_ilb();
@@ -10343,6 +10348,14 @@ static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
}
}
+ /*
+ * next_balance will be updated only when there is a need.
+ * When the CPU is attached to null domain for ex, it will not be
+ * updated.
+ */
+ if (likely(update_next_balance))
+ nohz.next_balance = next_balance;
+
/* Newly idle CPU doesn't need an update */
if (idle != CPU_NEWLY_IDLE) {
update_blocked_averages(this_cpu);
@@ -10363,14 +10376,6 @@ abort:
if (has_blocked_load)
WRITE_ONCE(nohz.has_blocked, 1);
- /*
- * next_balance will be updated only when there is a need.
- * When the CPU is attached to null domain for ex, it will not be
- * updated.
- */
- if (likely(update_next_balance))
- nohz.next_balance = next_balance;
-
return ret;
}