linux-kernel - Re: [PATCH] Allocate idle task for a CPU always on its local node

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Message-ID: <alpine.DEB.2.11.1605181028220.3851@nanos>
Date:	Wed, 18 May 2016 10:28:43 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andi Kleen <andi@...stfloor.org>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] Allocate idle task for a CPU always on its local node

On Tue, 17 May 2016, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> Linux pre-allocates the task structs of the idle tasks for all possible CPUs.
> This currently means they all end up on node 0. This also implies
> that the cache line of MWAIT, which is around the flags field in the task
> struct, are all located in node 0.
> 
> We see a noticeable performance improvement on Knights Landing CPUs when
> the cache lines used for MWAIT are located in the local nodes of the CPUs
> using them. I would expect this to give a (likely slight) improvement
> on other systems too.
> 
> The patch implements placing the idle task in the node of
> its CPUs, by passing the right target node to copy_process()
> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>

Acked-by: Thomas Gleixner <tglx@...utronix.de>