linux-kernel - Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs

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Message-ID: <c847e968-670a-ff6b-2f14-7fa4066955dd@intel.com>
Date:   Fri, 28 May 2021 09:17:41 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Hillf Danton <hdanton@...a.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>, "Tang, Feng" <feng.tang@...el.com>
Subject: Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active
 CPUs

On 5/28/21 8:18 AM, Mel Gorman wrote:
>> BTW, to do some of this testing, Feng was doing a plain old kernel
>> build.  On the one system where this got run, he noted a ~2% regression
>> in build times.  Nothing major, but you might want to be on the lookout
>> in case 0day or the other test harnesses find something similar once
>> this series gets to them.
>>
> What type of system was it?
> 
> I noticed minor differences for some thread counts on kernel compilations
> but for CascadeLake at least, it was mostly neutral. Below is an old test
> result based on a previous revision.

It's a Cascade Lake as well.  But, I never trust hardware at a hardware
company.  These could be preproduction CPUs or BIOS or both, or have
some bonkers configuration knob flipped.

It's also got a bunch of PMEM plugged and onlined, including the
_possibility_ of kernel data structures ended up on PMEM.  They *mostly*
don't end up there, but it does happen on occasion.

Anyway, I'll see if we can do some more runs with your latest version.
It looks like it's been picked up for -mm so 0day should be pounding on
it soon enough.