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Subject: Re: [PATCH v2 6/8] sched/idle: Move busy_cpu accounting to idle
 callback
To:     Valentin Schneider <valentin.schneider@arm.com>,
        Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Mel Gorman <mgorman@techsingularity.net>,
        Rik van Riel <riel@surriel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        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>,
        Aubrey Li <aubrey.li@intel.com>
References: <20210506164543.90688-1-srikar@linux.vnet.ibm.com>
 <20210506164543.90688-7-srikar@linux.vnet.ibm.com>
 <87tun91oaa.mognet@arm.com>
From:   Aubrey Li <aubrey.li@linux.intel.com>
Message-ID: <c4007fd3-e87b-5b19-6add-91ec4af8e83a@linux.intel.com>
Date:   Wed, 12 May 2021 08:32:26 +0800
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Hi Valentin,

On 5/11/21 7:51 PM, Valentin Schneider wrote:
> On 06/05/21 22:15, Srikar Dronamraju wrote:
>> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
>> index 8db40c8a6ad0..00e4669bb241 100644
>> --- a/kernel/sched/topology.c
>> +++ b/kernel/sched/topology.c
>> @@ -647,6 +647,7 @@ DEFINE_PER_CPU(int, sd_llc_id);
>>  #ifdef CONFIG_SCHED_SMT
>>  DEFINE_PER_CPU(int, smt_id);
>>  #endif
>> +DEFINE_PER_CPU(int, is_idle);
> 
> This + patch 8 immediately reminds me of Aubrey's patch:
> 
>   http://lore.kernel.org/r/1615872606-56087-1-git-send-email-aubrey.li@intel.com
> 
> last I looked it seemed OK, even the test bot seems happy. Aubrey, did you
> have any more work to do on that one (other than rebasing)?
> 

Thanks to mention this patch, in terms of the patch itself, I don't have any more
work, other than rebasing it to Rik's bring-back-select_idle_smt() patch.

But I have some other ideas based on this patch need to verify, for example, if we
have an idle_cpu mask when we scan the idle CPU, we should be able to remove SIS_PROP
feature at all. This removes scan cost computation and should reduce the task wakeup
latency. But I need a while to understand some benchmark regressions.

Thanks,
-Aubrey