linux-kernel - Re: [RFC PATCH v3 00/16] Core scheduling v3

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Date:   Fri, 19 Jul 2019 11:33:03 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Aaron Lu <aaron.lu@...ux.alibaba.com>
Cc:     Julien Desfossez <jdesfossez@...italocean.com>,
        Aubrey Li <aubrey.intel@...il.com>,
        Subhra Mazumdar <subhra.mazumdar@...cle.com>,
        Vineeth Remanan Pillai <vpillai@...italocean.com>,
        Nishanth Aravamudan <naravamudan@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul Turner <pjt@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Frédéric Weisbecker <fweisbec@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Greg Kerr <kerrnel@...gle.com>, Phil Auld <pauld@...hat.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [RFC PATCH v3 00/16] Core scheduling v3

On 7/18/19 10:52 PM, Aaron Lu wrote:
> On Thu, Jul 18, 2019 at 04:27:19PM -0700, Tim Chen wrote:
>>
>>
>> On 7/18/19 3:07 AM, Aaron Lu wrote:
>>> On Wed, Jun 19, 2019 at 02:33:02PM -0400, Julien Desfossez wrote:
>>
>>>
>>> With the below patch on top of v3 that makes use of util_avg to decide
>>> which task win, I can do all 8 steps and the final scores of the 2
>>> workloads are: 1796191 and 2199586. The score number are not close,
>>> suggesting some unfairness, but I can finish the test now...
>>
>> Aaron,
>>
>> Do you still see high variance in terms of workload throughput that
>> was a problem with the previous version?
> 
> Any suggestion how to measure this?
> It's not clear how Aubrey did his test, will need to take a look at
> sysbench.
> 
>>>
>>>  
>>>  }
>>> +
>>> +bool cfs_prio_less(struct task_struct *a, struct task_struct *b)
>>> +{
>>> +	struct sched_entity *sea = &a->se;
>>> +	struct sched_entity *seb = &b->se;
>>> +	bool samecore = task_cpu(a) == task_cpu(b);
>>
>>
>> Probably "samecpu" instead of "samecore" will be more accurate.
>> I think task_cpu(a) and task_cpu(b)
>> can be different, but still belong to the same cpu core.
> 
> Right, definitely, guess I'm brain damaged.
> 
>>
>>> +	struct task_struct *p;
>>> +	s64 delta;
>>> +
>>> +	if (samecore) {
>>> +		/* vruntime is per cfs_rq */
>>> +		while (!is_same_group(sea, seb)) {
>>> +			int sea_depth = sea->depth;
>>> +			int seb_depth = seb->depth;
>>> +
>>> +			if (sea_depth >= seb_depth)
>>
>> Should this be strictly ">" instead of ">=" ?
> 
> Same depth doesn't necessarily mean same group while the purpose here is
> to make sure they are in the same cfs_rq. When they are of the same
> depth but in different cfs_rqs, we will continue to go up till we reach
> rq->cfs.

Ah, I see what you are doing now.  Thanks for the clarification.

Tim