From: Aubrey Li <aubrey.li@linux.intel.com>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Mel Gorman <mgorman@techsingularity.net>,
Rik van Riel <riel@surriel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Valentin Schneider <valentin.schneider@arm.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Gautham R Shenoy <ego@linux.vnet.ibm.com>,
Parth Shah <parth@linux.ibm.com>
Subject: Re: [PATCH v2 6/8] sched/idle: Move busy_cpu accounting to idle callback
Date: Fri, 14 May 2021 12:11:50 +0800 [thread overview]
Message-ID: <5823f298-6fae-5a73-3ab8-f708d90a7e52@linux.intel.com> (raw)
In-Reply-To: <20210513073112.GV2633526@linux.vnet.ibm.com>
On 5/13/21 3:31 PM, Srikar Dronamraju wrote:
> * Aubrey Li <aubrey.li@linux.intel.com> [2021-05-12 16:08:24]:
>
>> On 5/7/21 12:45 AM, Srikar Dronamraju wrote:
>>> Currently we account nr_busy_cpus in no_hz idle functions.
>>> There is no reason why nr_busy_cpus should updated be in NO_HZ_COMMON
>>> configs only. Also scheduler can mark a CPU as non-busy as soon as an
>>> idle class task starts to run. Scheduler can then mark a CPU as busy
>>> as soon as its woken up from idle or a new task is placed on it's
>>> runqueue.
>>
>> IIRC, we discussed this before, if a SCHED_IDLE task is placed on the
>> CPU's runqueue, this CPU should be still taken as a wakeup target.
>>
>
> Yes, this CPU is still a wakeup target, its only when this CPU is busy, that
> we look at other CPUs
>
>> Also, for those frequent context-switching tasks with very short idle,
>> it's expensive for scheduler to mark idle/busy every time, that's why
>> my patch only marks idle every time and marks busy ratelimited in
>> scheduler tick.
>>
>
> I have tried few tasks with very short idle times and updating nr_busy
> everytime, doesnt seem to be impacting. Infact, it seems to help in picking
> the idler-llc more often.
>
How many CPUs in your LLC?
This is a system with 192 CPUs, 4 nodes and each node has 48 CPUs in LLC
domain.
It looks like for netperf both TCP and UDP cases have the notable change
under 2 x overcommit, it may be not interesting though.
hackbench(48 tasks per group)
=========
case load baseline(std%) compare%( std%)
process-pipe group-1 1.00 ( 6.74) -4.61 ( 8.97)
process-pipe group-2 1.00 ( 36.84) +11.53 ( 26.35)
process-pipe group-3 1.00 ( 24.97) +12.21 ( 19.05)
process-pipe group-4 1.00 ( 18.27) -2.62 ( 17.60)
process-pipe group-8 1.00 ( 4.33) -2.22 ( 3.08)
process-sockets group-1 1.00 ( 7.88) -20.26 ( 15.97)
process-sockets group-2 1.00 ( 5.38) -19.41 ( 9.25)
process-sockets group-3 1.00 ( 4.22) -5.70 ( 3.00)
process-sockets group-4 1.00 ( 1.44) -1.80 ( 0.79)
process-sockets group-8 1.00 ( 0.44) -2.86 ( 0.06)
threads-pipe group-1 1.00 ( 5.43) -3.69 ( 3.59)
threads-pipe group-2 1.00 ( 18.00) -2.69 ( 16.79)
threads-pipe group-3 1.00 ( 21.72) -9.01 ( 21.34)
threads-pipe group-4 1.00 ( 21.58) -6.43 ( 16.26)
threads-pipe group-8 1.00 ( 3.05) -0.15 ( 2.31)
threads-sockets group-1 1.00 ( 14.51) -5.35 ( 13.85)
threads-sockets group-2 1.00 ( 3.97) -24.15 ( 4.40)
threads-sockets group-3 1.00 ( 4.97) -9.05 ( 2.46)
threads-sockets group-4 1.00 ( 1.98) -3.44 ( 0.49)
threads-sockets group-8 1.00 ( 0.37) -2.13 ( 0.20)
netperf
=======
case load baseline(std%) compare%( std%)
TCP_RR thread-48 1.00 ( 3.84) -2.20 ( 3.83)
TCP_RR thread-96 1.00 ( 5.22) -4.97 ( 3.90)
TCP_RR thread-144 1.00 ( 7.97) -0.75 ( 4.39)
TCP_RR thread-192 1.00 ( 3.03) -0.67 ( 4.40)
TCP_RR thread-384 1.00 ( 22.27) -14.15 ( 36.28)
UDP_RR thread-48 1.00 ( 2.08) -0.39 ( 2.29)
UDP_RR thread-96 1.00 ( 2.48) -4.26 ( 16.06)
UDP_RR thread-144 1.00 ( 49.50) -3.28 ( 34.86)
UDP_RR thread-192 1.00 ( 6.39) +8.07 ( 88.15)
UDP_RR thread-384 1.00 ( 31.54) -12.76 ( 35.98)
next prev parent reply other threads:[~2021-05-14 4:12 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-06 16:45 [PATCH v2 0/8] sched/fair: wake_affine improvements Srikar Dronamraju
2021-05-06 16:45 ` [PATCH v2 1/8] sched/fair: Update affine statistics when needed Srikar Dronamraju
2021-05-07 16:08 ` Valentin Schneider
2021-05-07 17:05 ` Srikar Dronamraju
2021-05-11 11:51 ` Valentin Schneider
2021-05-11 16:22 ` Srikar Dronamraju
2021-05-06 16:45 ` [PATCH v2 2/8] sched/fair: Maintain the identity of idle-core Srikar Dronamraju
2021-05-11 11:51 ` Valentin Schneider
2021-05-11 16:27 ` Srikar Dronamraju
2021-05-06 16:45 ` [PATCH v2 3/8] sched/fair: Update idle-core more often Srikar Dronamraju
2021-05-06 16:45 ` [PATCH v2 4/8] sched/fair: Prefer idle CPU to cache affinity Srikar Dronamraju
2021-05-06 16:45 ` [PATCH v2 5/8] sched/fair: Use affine_idler_llc for wakeups across LLC Srikar Dronamraju
2021-05-06 16:45 ` [PATCH v2 6/8] sched/idle: Move busy_cpu accounting to idle callback Srikar Dronamraju
2021-05-11 11:51 ` Valentin Schneider
2021-05-11 16:55 ` Srikar Dronamraju
2021-05-12 0:32 ` Aubrey Li
2021-05-12 8:08 ` Aubrey Li
2021-05-13 7:31 ` Srikar Dronamraju
2021-05-14 4:11 ` Aubrey Li [this message]
2021-05-17 10:40 ` Srikar Dronamraju
2021-05-17 12:48 ` Aubrey Li
2021-05-17 12:57 ` Srikar Dronamraju
2021-05-18 0:59 ` Aubrey Li
2021-05-18 4:00 ` Srikar Dronamraju
2021-05-18 6:05 ` Aubrey Li
2021-05-18 7:18 ` Srikar Dronamraju
2021-05-19 9:43 ` Aubrey Li
2021-05-19 17:34 ` Srikar Dronamraju
2021-05-06 16:45 ` [PATCH v2 7/8] sched/fair: Remove ifdefs in waker_affine_idler_llc Srikar Dronamraju
2021-05-06 16:45 ` [PATCH v2 8/8] sched/fair: Dont iterate if no idle CPUs Srikar Dronamraju
2021-05-06 16:53 ` [PATCH v2 0/8] sched/fair: wake_affine improvements Srikar Dronamraju
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