Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 17 May 2021 16:10:58 +0530
From:   Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To:     Aubrey Li <aubrey.li@linux.intel.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
Message-ID: <20210517104058.GW2633526@linux.vnet.ibm.com>
Reply-To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
References: <20210506164543.90688-1-srikar@linux.vnet.ibm.com>
 <20210506164543.90688-7-srikar@linux.vnet.ibm.com>
 <47d29f1d-cea6-492a-5125-85db6bce0fa7@linux.intel.com>
 <20210513073112.GV2633526@linux.vnet.ibm.com>
 <5823f298-6fae-5a73-3ab8-f708d90a7e52@linux.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
In-Reply-To: <5823f298-6fae-5a73-3ab8-f708d90a7e52@linux.intel.com>
Precedence: bulk

* Aubrey Li <aubrey.li@linux.intel.com> [2021-05-14 12:11:50]:

> 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:

<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?


-- 
Thanks and Regards
Srikar Dronamraju