linux-kernel - Re: [PATCH 2/3] mm: Send one IPI per CPU to TLB flush multiple pages that were recently unmapped

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Message-ID: <553DA395.803@redhat.com>
Date:	Sun, 26 Apr 2015 22:48:53 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Mel Gorman <mgorman@...e.de>, Linux-MM <linux-mm@...ck.org>
CC:	Hugh Dickins <hughd@...gle.com>, Minchan Kim <minchan@...nel.org>,
	Dave Hansen <dave.hansen@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] mm: Send one IPI per CPU to TLB flush multiple pages
 that were recently unmapped

On 04/25/2015 01:45 PM, Mel Gorman wrote:
> An IPI is sent to flush remote TLBs when a page is unmapped that was
> recently accessed by other CPUs. There are many circumstances where this
> happens but the obvious one is kswapd reclaiming pages belonging to a
> running process as kswapd and the task are likely running on separate CPUs.

> It's still a noticeable improvement with vmstat showing interrupts went
> from roughly 500K per second to 45K per second.
> 
> The patch will have no impact on workloads with no memory pressure or
> have relatively few mapped pages.
> 
> Signed-off-by: Mel Gorman <mgorman@...e.de>

Reviewed-by: Rik van Riel <riel@...hat.com>


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