* [PATCH v2] sched/fair: fix nohz next idle balance
@ 2020-06-09 12:37 Vincent Guittot
2020-06-10 12:49 ` Peter Zijlstra
` (3 more replies)
0 siblings, 4 replies; 6+ messages in thread
From: Vincent Guittot @ 2020-06-09 12:37 UTC (permalink / raw)
To: mingo, peterz, juri.lelli, dietmar.eggemann, rostedt, bsegall,
mgorman, linux-kernel, iwtbavbm
Cc: valentin.schneider, Vincent Guittot
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.
Reported-by: Peng Liu <iwtbavbm@gmail.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
- Changes v2:
- use jiffies instead of incrementing nohz.next_balance to be sure of the
value. The change slipped out of the previous version.
kernel/sched/fair.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 0ed04d2a8959..832164d441dd 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10017,7 +10017,12 @@ 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();
@@ -10338,6 +10343,14 @@ 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);
@@ -10358,14 +10371,6 @@ static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
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;
}
--
2.17.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH v2] sched/fair: fix nohz next idle balance
2020-06-09 12:37 [PATCH v2] sched/fair: fix nohz next idle balance Vincent Guittot
@ 2020-06-10 12:49 ` Peter Zijlstra
2020-06-11 14:12 ` Valentin Schneider
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Peter Zijlstra @ 2020-06-10 12:49 UTC (permalink / raw)
To: Vincent Guittot
Cc: mingo, juri.lelli, dietmar.eggemann, rostedt, bsegall, mgorman,
linux-kernel, iwtbavbm, valentin.schneider
On Tue, Jun 09, 2020 at 02:37:48PM +0200, Vincent Guittot wrote:
> 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.
>
> Reported-by: Peng Liu <iwtbavbm@gmail.com>
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Thanks
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH v2] sched/fair: fix nohz next idle balance
2020-06-09 12:37 [PATCH v2] sched/fair: fix nohz next idle balance Vincent Guittot
2020-06-10 12:49 ` Peter Zijlstra
@ 2020-06-11 14:12 ` Valentin Schneider
2020-06-11 14:28 ` Peter Zijlstra
2020-06-11 14:43 ` Mel Gorman
2020-06-16 12:21 ` [tip: sched/core] sched/fair: Fix NOHZ " tip-bot2 for Vincent Guittot
3 siblings, 1 reply; 6+ messages in thread
From: Valentin Schneider @ 2020-06-11 14:12 UTC (permalink / raw)
To: Vincent Guittot
Cc: mingo, peterz, juri.lelli, dietmar.eggemann, rostedt, bsegall,
mgorman, linux-kernel, iwtbavbm
On 09/06/20 13:37, Vincent Guittot wrote:
> 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.
>
> Reported-by: Peng Liu <iwtbavbm@gmail.com>
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
FWIW:
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Do we want a Fixes: tag for this? I'm thinking
b7031a02ec75 ("sched/fair: Add NOHZ_STATS_KICK")
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH v2] sched/fair: fix nohz next idle balance
2020-06-11 14:12 ` Valentin Schneider
@ 2020-06-11 14:28 ` Peter Zijlstra
0 siblings, 0 replies; 6+ messages in thread
From: Peter Zijlstra @ 2020-06-11 14:28 UTC (permalink / raw)
To: Valentin Schneider
Cc: Vincent Guittot, mingo, juri.lelli, dietmar.eggemann, rostedt,
bsegall, mgorman, linux-kernel, iwtbavbm
On Thu, Jun 11, 2020 at 03:12:11PM +0100, Valentin Schneider wrote:
>
> On 09/06/20 13:37, Vincent Guittot wrote:
> > 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.
> >
> > Reported-by: Peng Liu <iwtbavbm@gmail.com>
> > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
>
> FWIW:
> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
>
> Do we want a Fixes: tag for this? I'm thinking
> b7031a02ec75 ("sched/fair: Add NOHZ_STATS_KICK")
Done, thanks!
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] sched/fair: fix nohz next idle balance
2020-06-09 12:37 [PATCH v2] sched/fair: fix nohz next idle balance Vincent Guittot
2020-06-10 12:49 ` Peter Zijlstra
2020-06-11 14:12 ` Valentin Schneider
@ 2020-06-11 14:43 ` Mel Gorman
2020-06-16 12:21 ` [tip: sched/core] sched/fair: Fix NOHZ " tip-bot2 for Vincent Guittot
3 siblings, 0 replies; 6+ messages in thread
From: Mel Gorman @ 2020-06-11 14:43 UTC (permalink / raw)
To: Vincent Guittot
Cc: mingo, peterz, juri.lelli, dietmar.eggemann, rostedt, bsegall,
linux-kernel, iwtbavbm, valentin.schneider
On Tue, Jun 09, 2020 at 02:37:48PM +0200, Vincent Guittot wrote:
> 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.
>
> Reported-by: Peng Liu <iwtbavbm@gmail.com>
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Acked-by: Mel Gorman <mgorman@suse.de>
--
Mel Gorman
SUSE Labs
^ permalink raw reply [flat|nested] 6+ messages in thread* [tip: sched/core] sched/fair: Fix NOHZ next idle balance
2020-06-09 12:37 [PATCH v2] sched/fair: fix nohz next idle balance Vincent Guittot
` (2 preceding siblings ...)
2020-06-11 14:43 ` Mel Gorman
@ 2020-06-16 12:21 ` tip-bot2 for Vincent Guittot
3 siblings, 0 replies; 6+ messages in thread
From: tip-bot2 for Vincent Guittot @ 2020-06-16 12:21 UTC (permalink / raw)
To: linux-tip-commits
Cc: Peng Liu, Vincent Guittot, Peter Zijlstra (Intel),
Valentin Schneider, Mel Gorman, x86, LKML
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 3ea2f097b17e13a8280f1f9386c331b326a3dbef
Gitweb: https://git.kernel.org/tip/3ea2f097b17e13a8280f1f9386c331b326a3dbef
Author: Vincent Guittot <vincent.guittot@linaro.org>
AuthorDate: Tue, 09 Jun 2020 14:37:48 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 15 Jun 2020 14:10:04 +02:00
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 <iwtbavbm@gmail.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20200609123748.18636-1-vincent.guittot@linaro.org
---
kernel/sched/fair.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a785a9b..295c9ff 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;
}
^ permalink raw reply related [flat|nested] 6+ messages in thread
end of thread, other threads:[~2020-06-16 12:23 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2020-06-09 12:37 [PATCH v2] sched/fair: fix nohz next idle balance Vincent Guittot
2020-06-10 12:49 ` Peter Zijlstra
2020-06-11 14:12 ` Valentin Schneider
2020-06-11 14:28 ` Peter Zijlstra
2020-06-11 14:43 ` Mel Gorman
2020-06-16 12:21 ` [tip: sched/core] sched/fair: Fix NOHZ " tip-bot2 for Vincent Guittot
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