From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: Josef Bacik <jbacik@fb.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
riel@redhat.com, mingo@redhat.com, linux-kernel@vger.kernel.org,
morten.rasmussen@arm.com, kernel-team <Kernel-team@fb.com>
Subject: Re: [PATCH RESEND] sched: prefer an idle cpu vs an idle sibling for BALANCE_WAKE
Date: Fri, 03 Jul 2015 11:29:07 +0200 [thread overview]
Message-ID: <1435915747.6658.9.camel@gmail.com> (raw)
In-Reply-To: <1435905658.6418.52.camel@gmail.com>
On Fri, 2015-07-03 at 08:40 +0200, Mike Galbraith wrote:
> Hm. Seems what this load should like best is if we detect 1:N, skip all
> of the routine gyrations, ie move the N (workers) infrequently, expend
> search cycles frequently only on the 1 (dispatch).
>
> Ponder..
While taking a refresher peek at the wake_wide() thing, seems it's not
really paying attention when the waker of many is awakened. I wonder if
your load would see more benefit if it watched like so.. rashly assuming
I didn't wreck it completely (iow, completely untested).
---
kernel/sched/fair.c | 36 ++++++++++++++++++++++--------------
1 file changed, 22 insertions(+), 14 deletions(-)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4586,10 +4586,23 @@ static void record_wakee(struct task_str
current->wakee_flips >>= 1;
current->wakee_flip_decay_ts = jiffies;
}
+ if (time_after(jiffies, p->wakee_flip_decay_ts + HZ)) {
+ p->wakee_flips >>= 1;
+ p->wakee_flip_decay_ts = jiffies;
+ }
if (current->last_wakee != p) {
current->last_wakee = p;
current->wakee_flips++;
+ /*
+ * Flip the buddy as well. It's the ratio of flips
+ * with a socket size decayed cutoff that determines
+ * whether the pair are considered to be part of 1:N
+ * or M*N loads of a size that we need to spread, so
+ * ensure flips of both load components. The waker
+ * of many will have many more flips than its wakees.
+ */
+ p->wakee_flips++;
}
}
@@ -4732,24 +4745,19 @@ static long effective_load(struct task_g
static int wake_wide(struct task_struct *p)
{
+ unsigned long max = max(current->wakee_flips, p->wakee_flips);
+ unsigned long min = min(current->wakee_flips, p->wakee_flips);
int factor = this_cpu_read(sd_llc_size);
/*
- * Yeah, it's the switching-frequency, could means many wakee or
- * rapidly switch, use factor here will just help to automatically
- * adjust the loose-degree, so bigger node will lead to more pull.
+ * Yeah, it's a switching-frequency heuristic, and could mean the
+ * intended many wakees/waker relationship, or rapidly switching
+ * between a few. Use factor to try to automatically adjust such
+ * that the load spreads when it grows beyond what will fit in llc.
*/
- if (p->wakee_flips > factor) {
- /*
- * wakee is somewhat hot, it needs certain amount of cpu
- * resource, so if waker is far more hot, prefer to leave
- * it alone.
- */
- if (current->wakee_flips > (factor * p->wakee_flips))
- return 1;
- }
-
- return 0;
+ if (min < factor)
+ return 0;
+ return max > min * factor;
}
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
next prev parent reply other threads:[~2015-07-03 9:29 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-27 21:22 [PATCH RESEND] sched: prefer an idle cpu vs an idle sibling for BALANCE_WAKE Josef Bacik
2015-05-28 3:46 ` Mike Galbraith
2015-05-28 9:49 ` Morten Rasmussen
2015-05-28 10:57 ` Mike Galbraith
2015-05-28 11:48 ` Morten Rasmussen
2015-05-28 11:49 ` Mike Galbraith
2015-05-28 10:21 ` Peter Zijlstra
2015-05-28 11:05 ` Peter Zijlstra
2015-05-28 14:27 ` Josef Bacik
2015-05-29 21:03 ` Josef Bacik
2015-05-30 3:55 ` Mike Galbraith
2015-06-01 19:38 ` Josef Bacik
2015-06-01 20:42 ` Peter Zijlstra
2015-06-01 21:03 ` Josef Bacik
2015-06-02 17:12 ` Josef Bacik
2015-06-03 14:12 ` Rik van Riel
2015-06-03 14:24 ` Peter Zijlstra
2015-06-03 14:49 ` Josef Bacik
2015-06-03 15:30 ` Mike Galbraith
2015-06-03 15:57 ` Josef Bacik
2015-06-03 16:53 ` Mike Galbraith
2015-06-03 17:16 ` Josef Bacik
2015-06-03 17:43 ` Mike Galbraith
2015-06-03 20:34 ` Josef Bacik
2015-06-04 4:52 ` Mike Galbraith
2015-06-01 22:15 ` Rik van Riel
2015-06-11 20:33 ` Josef Bacik
2015-06-12 3:42 ` Rik van Riel
2015-06-12 5:35 ` Mike Galbraith
2015-06-17 18:06 ` Josef Bacik
2015-06-18 0:55 ` Mike Galbraith
2015-06-18 3:46 ` Josef Bacik
2015-06-18 4:12 ` Mike Galbraith
2015-07-02 17:44 ` Josef Bacik
2015-07-03 6:40 ` Mike Galbraith
2015-07-03 9:29 ` Mike Galbraith [this message]
2015-07-04 15:57 ` Mike Galbraith
2015-07-05 7:17 ` Mike Galbraith
2015-07-06 5:13 ` Mike Galbraith
2015-07-06 14:34 ` Josef Bacik
2015-07-06 18:36 ` Mike Galbraith
2015-07-06 19:41 ` Josef Bacik
2015-07-07 4:01 ` Mike Galbraith
2015-07-07 9:43 ` [patch] " Mike Galbraith
2015-07-07 13:40 ` Josef Bacik
2015-07-07 15:24 ` Mike Galbraith
2015-07-07 17:06 ` Josef Bacik
2015-07-08 6:13 ` [patch] sched: beef up wake_wide() Mike Galbraith
2015-07-09 13:26 ` Peter Zijlstra
2015-07-09 14:07 ` Mike Galbraith
2015-07-09 14:46 ` Mike Galbraith
2015-07-10 5:19 ` Mike Galbraith
2015-07-10 13:41 ` Josef Bacik
2015-07-10 20:59 ` Josef Bacik
2015-07-11 3:11 ` Mike Galbraith
2015-07-13 13:53 ` Josef Bacik
2015-07-14 11:19 ` Peter Zijlstra
2015-07-14 13:49 ` Mike Galbraith
2015-07-14 14:07 ` Peter Zijlstra
2015-07-14 14:17 ` Mike Galbraith
2015-07-14 15:04 ` Peter Zijlstra
2015-07-14 15:39 ` Mike Galbraith
2015-07-14 16:01 ` Josef Bacik
2015-07-14 17:59 ` Mike Galbraith
2015-07-15 17:11 ` Josef Bacik
2015-08-03 17:07 ` [tip:sched/core] sched/fair: Beef " tip-bot for Mike Galbraith
2015-05-28 11:16 ` [PATCH RESEND] sched: prefer an idle cpu vs an idle sibling for BALANCE_WAKE Mike Galbraith
2015-05-28 11:49 ` Ingo Molnar
2015-05-28 12:15 ` Mike Galbraith
2015-05-28 12:19 ` Peter Zijlstra
2015-05-28 12:29 ` Ingo Molnar
2015-05-28 15:22 ` David Ahern
2015-05-28 11:55 ` Srikar Dronamraju
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