linux-kernel - Re: [PATCH v3 0/2] sched: Minor changes for rd->overload access

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Message-ID: <ZgKApcWeuwxc2+WO@gmail.com>
Date: Tue, 26 Mar 2024 09:00:37 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>
Cc: peterz@...radead.org, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, qyousef@...alina.io,
	linux-kernel@...r.kernel.org, vschneid@...hat.com
Subject: Re: [PATCH v3 0/2] sched: Minor changes for rd->overload access


* Shrikanth Hegde <sshegde@...ux.ibm.com> wrote:

> 
> 
> On 3/25/24 4:06 PM, Ingo Molnar wrote:
> > 
> > * Shrikanth Hegde <sshegde@...ux.ibm.com> wrote:
> > 
> >> v2 -> v3:
> >> - Wrapped check for value change inside ser_rd_overload_status
> >>   as suggested by Qais.
> >> - Added reviewed-by tags.
> >>
> >> v1 -> v2:
> >> - dropped Fixes tag.
> >> - Added one of the perf probes in the changelog for reference.
> >> - Added reviewed-by tags.
> >>
> >> tl;dr
> >> When running workloads in large systems, it was observed that access to
> >> rd->overload was taking time. It would be better to check the value
> >> before updating since value changes less often. Patch 1/2 does that.
> >> With patch updates happen only if necessary. CPU Bus traffic reduced a
> >> bit. No significant gains in workload performance.
> > 
> > Could you please post this against the latest scheduler tree, ie. tip:sched/core?
> > 
> > Thanks,
> > 
> > 	Ingo
> 
> Hi Ingo. I had mentioned the same in cover letter. Sorry if I didn't 
> mention it in the correct place. 
> 
> *These patches depend on below to be applied first*
> https://lore.kernel.org/all/20240307085725.444486-1-sshegde@linux.ibm.com/
> 
> After that the above patch would apply.

OK, I missed that, but I don't really like patch #3 of that other series, 
so we'll need to address that first.

Thanks,

	Ingo