linux-kernel - Re: [PATCH 10/13] x86: mm: Enable deferred struct page initialisation on x86-64

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Message-ID: <20150423092327.GJ14842@suse.de>
Date:	Thu, 23 Apr 2015 10:23:27 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Linux-MM <linux-mm@...ck.org>, Nathan Zimmer <nzimmer@....com>,
	Dave Hansen <dave.hansen@...el.com>,
	Waiman Long <waiman.long@...com>,
	Scott Norton <scott.norton@...com>,
	Daniel J Blueman <daniel@...ascale.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 10/13] x86: mm: Enable deferred struct page
 initialisation on x86-64

On Wed, Apr 22, 2015 at 04:45:00PM -0700, Andrew Morton wrote:
> On Wed, 22 Apr 2015 18:07:50 +0100 Mel Gorman <mgorman@...e.de> wrote:
> 
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -32,6 +32,7 @@ config X86
> >  	select HAVE_UNSTABLE_SCHED_CLOCK
> >  	select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
> >  	select ARCH_SUPPORTS_INT128 if X86_64
> > +	select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT if X86_64 && NUMA
> 
> Put this in the "config X86_64" section and skip the "X86_64 &&"?
> 

Done.

> Can we omit the whole defer_meminit= thing and permanently enable the
> feature?  That's simpler, provides better test coverage and is, we
> hope, faster.
> 

Yes. The intent was to have a workaround if there were any failures like
Waiman's vmalloc failures in an earlier version but they are bugs that
should be fixed.

> And can this be used on non-NUMA?  Presumably that won't speed things
> up any if we're bandwidth limited but again it's simpler and provides
> better coverage.

Nothing prevents it. There is less opportunity for parallelism but
improving coverage is desirable.

-- 
Mel Gorman
SUSE Labs
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