linux-kernel - Re: [PATCH 6/7] mm: parallelize deferred_init

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Date:   Wed, 6 May 2020 18:21:27 -0400
From:   Daniel Jordan <daniel.m.jordan@...cle.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     Daniel Jordan <daniel.m.jordan@...cle.com>,
        Josh Triplett <josh@...htriplett.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Hildenbrand <david@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jonathan Corbet <corbet@....net>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Michal Hocko <mhocko@...nel.org>, Pavel Machek <pavel@....cz>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Shile Zhang <shile.zhang@...ux.alibaba.com>,
        Tejun Heo <tj@...nel.org>, Zi Yan <ziy@...dia.com>,
        linux-crypto@...r.kernel.org, linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/7] mm: parallelize deferred_init_memmap()

On Tue, May 05, 2020 at 07:55:43AM -0700, Alexander Duyck wrote:
> One question about this data. What is the power management
> configuration on the systems when you are running these tests? I'm
> just curious if CPU frequency scaling, C states, and turbo are
> enabled?

Yes, intel_pstate is loaded in active mode without hwp and with turbo enabled
(those power management docs are great by the way!) and intel_idle is in use
too.

> I ask because that is what I have seen usually make the
> difference in these kind of workloads as the throughput starts
> dropping off as you start seeing the core frequency lower and more
> cores become active.

If I follow, you're saying there's a chance performance would improve with the
above disabled, but how often would a system be configured that way?  Even if
it were faster, the machine is configured how it's configured, or am I missing
your point?