linux-kernel - Re: BUG Report: Fork benchmark drop by 30% on aarch64

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Message-ID: <c8a9710a-e62e-4a8f-826f-f3092824e94e@arm.com>
Date: Mon, 3 Mar 2025 11:06:27 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Hagar Hemdan <hagarhem@...zon.com>
Cc: abuehaze@...zon.com, linux-kernel@...r.kernel.org, wuchi.zero@...il.com
Subject: Re: BUG Report: Fork benchmark drop by 30% on aarch64

On 28/02/2025 20:39, Hagar Hemdan wrote:
> On Mon, Feb 17, 2025 at 11:51:45PM +0100, Dietmar Eggemann wrote:
>> On 13/02/2025 19:55, Dietmar Eggemann wrote:
>>> On 11/02/2025 22:40, Hagar Hemdan wrote:
>>>> On Tue, Feb 11, 2025 at 05:27:47PM +0100, Dietmar Eggemann wrote:
>>>>> On 10/02/2025 22:31, Hagar Hemdan wrote:
>>>>>> On Mon, Feb 10, 2025 at 11:38:51AM +0100, Dietmar Eggemann wrote:
>>>>>>> On 07/02/2025 12:07, Hagar Hemdan wrote:
>>>>>>>> On Fri, Feb 07, 2025 at 10:14:54AM +0100, Dietmar Eggemann wrote:

[...]

>> './Run -c 4 spawn' on AWS instance (m7gd.16xlarge) with v6.13, 'mem=16G
>> maxcpus=4 nr_cpus=4' and Ubuntu '22.04.5 LTS':
>>
>> CFG_SCHED_AUTOGROUP | sched_ag_enabled | eff6c8ce8d4d | Fork (lps)
>>
>>    	y	             1		   y            21005 (27120 **)
>> 	y		     0		   y            21059 (27012 **)
>> 	n		     -		   y            21299
>> 	y		     1		   n	        27745 *
>> 	y		     0		   n	        27493 *
>> 	n		     -		   n	        20928
>>
>> (*) So here the higher numbers are only achieved when
>> 'sched_autogroup_exit_task() -> sched_move_task() ->
>> sched_change_group() is called for the 'spawn' tasks.
>>
>> (**) When I apply the fix from
>> https://lkml.kernel.org/r/4a9cc5ab-c538-4427-8a7c-99cb317a283f@arm.com.
> 
> This is currently impacting our kernel, do you
> have any concerns to submit this fix upstream?

Will send it out after the analysis now done. See the other email from
today.