From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Ming Lei <ming.lei@redhat.com>,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org,
Jeff Moyer <jmoyer@redhat.com>,
Dave Chinner <dchinner@redhat.com>,
Eric Sandeen <sandeen@redhat.com>, Christoph Hellwig <hch@lst.de>,
Jens Axboe <axboe@kernel.dk>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>, Tejun Heo <tj@kernel.org>
Subject: Re: single aio thread is migrated crazily by scheduler
Date: Mon, 18 Nov 2019 21:56:33 +0530 [thread overview]
Message-ID: <20191118162633.GC32306@linux.vnet.ibm.com> (raw)
In-Reply-To: <20191115234005.GO4614@dread.disaster.area>
* Dave Chinner <david@fromorbit.com> [2019-11-16 10:40:05]:
> On Fri, Nov 15, 2019 at 03:08:43PM +0800, Ming Lei wrote:
> > On Fri, Nov 15, 2019 at 03:56:34PM +1100, Dave Chinner wrote:
> > > On Fri, Nov 15, 2019 at 09:08:24AM +0800, Ming Lei wrote:
> > I can reproduce the issue with 4k block size on another RH system, and
> > the login info of that system has been shared to you in RH BZ.
> >
> > 1)
>
> Almost all the fio task migrations are coming from migration/X
> kernel threads. i.e it's the scheduler active balancing that is
> causing the fio thread to bounce around.
>
Can we try with the below patch.
--
Thanks and Regards
Srikar Dronamraju
--->8-----------------------------8<----------------------------------
From 9687c1447532558aa564bd2e471b7987d6bda70f Mon Sep 17 00:00:00 2001
From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Date: Tue, 2 Jul 2019 16:38:29 -0500
Subject: [PATCH] sched/fair: Avoid active balance on small load imbalance
Skip active load balance when destination CPU is busy and the imbalance
is small and fix_small_imabalance is unable to calculate minor
imbalance. Its observed that active load balances can lead to ping-pong
of tasks between two CPUs.
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
kernel/sched/fair.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3599bdcab395..0db380c8eb6c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7094,6 +7094,7 @@ enum group_type {
#define LBF_SOME_PINNED 0x08
#define LBF_NOHZ_STATS 0x10
#define LBF_NOHZ_AGAIN 0x20
+#define LBF_SMALL_IMBL 0x40
struct lb_env {
struct sched_domain *sd;
@@ -8386,6 +8387,8 @@ void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
/* Move if we gain throughput */
if (capa_move > capa_now)
env->imbalance = busiest->load_per_task;
+ else if (env->idle == CPU_NOT_IDLE)
+ env->flags |= LBF_SMALL_IMBL;
}
/**
@@ -8466,7 +8469,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
* moved
*/
if (env->imbalance < busiest->load_per_task)
- return fix_small_imbalance(env, sds);
+ fix_small_imbalance(env, sds);
}
/******* find_busiest_group() helpers end here *********************/
@@ -8732,6 +8735,13 @@ static int need_active_balance(struct lb_env *env)
if (voluntary_active_balance(env))
return 1;
+ /*
+ * Destination CPU is not idle and fix_small_imbalance is unable
+ * to calculate even minor imbalances, skip active balance.
+ */
+ if (env->flags & LBF_SMALL_IMBL)
+ return 0;
+
return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}
--
2.18.1
next prev parent reply other threads:[~2019-11-18 16:26 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-14 11:31 single aio thread is migrated crazily by scheduler Ming Lei
2019-11-14 13:14 ` Peter Zijlstra
2019-11-15 0:09 ` Ming Lei
2019-11-15 14:16 ` Ming Lei
2019-11-14 23:54 ` Dave Chinner
2019-11-15 1:08 ` Ming Lei
2019-11-15 4:56 ` Dave Chinner
2019-11-15 7:08 ` Ming Lei
2019-11-15 23:40 ` Dave Chinner
2019-11-16 6:31 ` Ming Lei
2019-11-18 9:21 ` Peter Zijlstra
2019-11-18 14:54 ` Vincent Guittot
2019-11-18 20:40 ` Dave Chinner
2019-11-20 19:16 ` Peter Zijlstra
2019-11-20 22:03 ` Phil Auld
2019-11-21 4:12 ` Ming Lei
2019-11-21 14:12 ` Phil Auld
2019-11-21 15:02 ` Boaz Harrosh
2019-11-21 16:19 ` Jens Axboe
2019-12-09 16:58 ` Srikar Dronamraju
2019-11-21 22:10 ` Dave Chinner
2019-11-21 13:29 ` Peter Zijlstra
2019-11-21 14:21 ` Phil Auld
2019-12-09 16:51 ` Srikar Dronamraju
2019-12-09 23:17 ` Dave Chinner
2019-12-10 3:27 ` Srikar Dronamraju
2019-12-10 5:43 ` [PATCH v2] sched/core: Preempt current task in favour of bound kthread Srikar Dronamraju
2019-12-10 9:26 ` Peter Zijlstra
2019-12-10 9:33 ` Peter Zijlstra
2019-12-10 10:18 ` Srikar Dronamraju
2019-12-10 10:16 ` Srikar Dronamraju
2019-12-10 9:43 ` Vincent Guittot
2019-12-10 10:11 ` Srikar Dronamraju
2019-12-10 11:02 ` Vincent Guittot
2019-12-10 17:23 ` [PATCH v3] " Srikar Dronamraju
2019-12-11 17:38 ` [PATCH v4] " Srikar Dronamraju
2019-12-11 22:46 ` Dave Chinner
2019-12-12 10:10 ` Peter Zijlstra
2019-12-12 10:14 ` Peter Zijlstra
2019-12-12 10:23 ` Peter Zijlstra
2019-12-12 11:20 ` Vincent Guittot
2019-12-12 13:12 ` Peter Zijlstra
2019-12-12 15:07 ` Srikar Dronamraju
2019-12-12 15:15 ` Peter Zijlstra
2019-12-13 5:32 ` Srikar Dronamraju
2019-11-18 16:26 ` Srikar Dronamraju [this message]
2019-11-18 21:18 ` single aio thread is migrated crazily by scheduler Dave Chinner
2019-11-19 8:54 ` Ming Lei
[not found] ` <20191128094003.752-1-hdanton@sina.com>
2019-11-28 9:53 ` Vincent Guittot
2019-12-02 2:46 ` Ming Lei
2019-12-02 4:02 ` Dave Chinner
2019-12-02 4:22 ` Ming Lei
2019-12-02 13:45 ` Vincent Guittot
2019-12-02 21:22 ` Phil Auld
2019-12-03 9:45 ` Vincent Guittot
2019-12-04 13:50 ` Ming Lei
2019-12-02 23:53 ` Dave Chinner
2019-12-03 0:18 ` Ming Lei
2019-12-03 13:34 ` Vincent Guittot
2019-12-02 7:39 ` Juri Lelli
2019-12-02 3:08 ` Dave Chinner
[not found] ` <20191202090158.15016-1-hdanton@sina.com>
2019-12-02 23:06 ` Dave Chinner
[not found] ` <20191203131514.5176-1-hdanton@sina.com>
2019-12-03 22:29 ` Dave Chinner
[not found] ` <20191204102903.896-1-hdanton@sina.com>
2019-12-04 22:59 ` Dave Chinner
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