linux-kernel - Re: [PATCH v2 6/8] sched/idle: Move busy

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Date:   Tue, 18 May 2021 08:59:00 +0800
From:   Aubrey Li <aubrey.li@...ux.intel.com>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Rik van Riel <riel@...riel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Valentin Schneider <valentin.schneider@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Gautham R Shenoy <ego@...ux.vnet.ibm.com>,
        Parth Shah <parth@...ux.ibm.com>
Subject: Re: [PATCH v2 6/8] sched/idle: Move busy_cpu accounting to idle
 callback

On 5/17/21 8:57 PM, Srikar Dronamraju wrote:
> * Aubrey Li <aubrey.li@...ux.intel.com> [2021-05-17 20:48:46]:
> 
>> On 5/17/21 6:40 PM, Srikar Dronamraju wrote:
>>> * Aubrey Li <aubrey.li@...ux.intel.com> [2021-05-14 12:11:50]:
>>>
>>>> On 5/13/21 3:31 PM, Srikar Dronamraju wrote:
>>>>> * Aubrey Li <aubrey.li@...ux.intel.com> [2021-05-12 16:08:24]:
>>>>>> On 5/7/21 12:45 AM, Srikar Dronamraju wrote:
>>>
>>> <snip>
>>>
>>>>>> 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?
>>>
>>> I have tried with X86, 48 CPUs, 2 nodes, each having 24 CPUs in LLC
>>> +
>>> POWER10, Multiple CPUs with 4 CPUs in LLC
>>> +
>>> POWER9, Multiple CPUs with 8 CPUs in LLC
>>>
>>>>
>>>> This is a system with 192 CPUs, 4 nodes and each node has 48 CPUs in LLC
>>>> domain.
>>>>
>>>
>>> Okay,
>>>
>>>> It looks like for netperf both TCP and UDP cases have the notable change
>>>> under 2 x overcommit, it may be not interesting though.
>>>>
>>>>
>>>
>>> I believe the extra load on this 24 core LLC could be because we may end up
>>> trying to set the idle-core, even when there is no idle core available.
>>>
>>> If possible, can you please give a try with v3 with the call to
>>> set_next_idle_core commented out?
>>>
>>>
>>
>> v3 seems not be applicable on tip/sched/core 915a2bc3c6b7?
> 
> I had applied on top of 2ea46c6fc9452ac100ad907b051d797225847e33
> which was tag: sched-core-2021-04-28
> 
> The only conflict you get on today's tip is Gautham's one line patch.
> Gautham's patch replaced 'this' with 'target'.
> 
> The 2nd patch does away with that line
> 

This is v3. It looks like hackbench gets better. And netperf still has
some notable changes under 2 x overcommit cases.


hackbench (48 tasks per group)
=========
case            	load    	baseline(std%)	compare%( std%)
process-pipe    	group-1 	 1.00 (  4.51)	 +1.36 (  4.26)
process-pipe    	group-2 	 1.00 ( 18.73)	 -9.66 ( 31.15)
process-pipe    	group-3 	 1.00 ( 23.67)	 +8.52 ( 21.13)
process-pipe    	group-4 	 1.00 ( 14.65)	+17.12 ( 25.23)
process-pipe    	group-8 	 1.00 (  3.11)	+16.41 (  5.94)
process-sockets 	group-1 	 1.00 (  8.83)	 +1.53 ( 11.93)
process-sockets 	group-2 	 1.00 (  5.32)	-15.43 (  7.17)
process-sockets 	group-3 	 1.00 (  4.79)	 -4.14 (  1.90)
process-sockets 	group-4 	 1.00 (  2.39)	 +4.37 (  1.31)
process-sockets 	group-8 	 1.00 (  0.38)	 +4.41 (  0.05)
threads-pipe    	group-1 	 1.00 (  3.06)	 -1.57 (  3.71)
threads-pipe    	group-2 	 1.00 ( 17.41)	 -2.16 ( 15.29)
threads-pipe    	group-3 	 1.00 ( 17.94)	+19.86 ( 13.24)
threads-pipe    	group-4 	 1.00 ( 15.38)	 +3.71 ( 11.97)
threads-pipe    	group-8 	 1.00 (  2.72)	+13.40 (  8.43)
threads-sockets 	group-1 	 1.00 (  8.51)	 -2.73 ( 17.48)
threads-sockets 	group-2 	 1.00 (  5.44)	-12.04 (  5.91)
threads-sockets 	group-3 	 1.00 (  4.38)	 -5.00 (  1.48)
threads-sockets 	group-4 	 1.00 (  1.08)	 +4.46 (  1.15)
threads-sockets 	group-8 	 1.00 (  0.61)	 +5.12 (  0.20)

netperf
=======
case            	load    	baseline(std%)	compare%( std%)
TCP_RR          	thread-48	 1.00 (  3.79)	 +4.69 (  4.03)
TCP_RR          	thread-96	 1.00 (  4.98)	 -6.74 (  3.59)
TCP_RR          	thread-144	 1.00 (  6.04)	 -2.36 (  3.57)
TCP_RR          	thread-192	 1.00 (  4.97)	 -0.44 (  4.89)
TCP_RR          	thread-384	 1.00 ( 19.87)	-19.12 ( 28.99)
UDP_RR          	thread-48	 1.00 ( 12.54)	 -2.73 (  1.59)
UDP_RR          	thread-96	 1.00 (  6.51)	 -6.66 ( 10.42)
UDP_RR          	thread-144	 1.00 ( 45.41)	 -3.81 ( 31.37)
UDP_RR          	thread-192	 1.00 ( 32.06)	 +3.07 ( 71.89)
UDP_RR          	thread-384	 1.00 ( 29.57)	-21.52 ( 35.50)