linux-kernel - Re: [PATCH] mm: meminit: Finish initialisation of struct pages before basic setup

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Date:	Fri, 26 Jun 2015 11:16:00 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Nathan Zimmer <nzimmer@....com>
Cc:	Daniel J Blueman <daniel@...ascale.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Waiman Long <waiman.long@...com>,
	Dave Hansen <dave.hansen@...el.com>,
	Scott Norton <scott.norton@...com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Steffen Persvold <sp@...ascale.com>
Subject: Re: [PATCH] mm: meminit: Finish initialisation of struct pages
 before basic setup

On Wed, Jun 24, 2015 at 05:50:28PM -0500, Nathan Zimmer wrote:
> From e18aa6158a60c2134b4eef93c856f3b5b250b122 Mon Sep 17 00:00:00 2001
> From: Nathan Zimmer <nzimmer@....com>
> Date: Thu, 11 Jun 2015 10:47:39 -0500
> Subject: [RFC] Avoid the contention in set_cpus_allowed
> 
> Noticing some scaling issues at larger box sizes (64 nodes+) I found that in some
> cases we are spending significant amounts of time in set_cpus_allowed_ptr.
> 
> My assumption is that it is getting stuck on migration.
> So if we create the thread on the target node and restrict cpus before we start
> the thread then we don't have to suffer migration.
> 
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Waiman Long <waiman.long@...com
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Scott Norton <scott.norton@...com>
> Cc: Daniel J Blueman <daniel@...ascale.com>
> Signed-off-by: Nathan Zimmer <nzimmer@....com>
> 

I asked yesterday if set_cpus_allowed_ptr() was required and I made a
mistake because it is. The node parameter for kthread_create_on_node()
controls where it gets created but not how it is scheduled after that.
Sorry for the noise. The patch makes sense to me now, lets see if it
helps Daniel.


-- 
Mel Gorman
SUSE Labs
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