linux-kernel - Re: [PATCH] mm, page_alloc: Use static global work

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Message-ID: <004201d276ee$0f20fd80$2d62f880$@alibaba-inc.com>
Date:   Wed, 25 Jan 2017 17:33:16 +0800
From:   "Hillf Danton" <hillf.zj@...baba-inc.com>
To:     "'Mel Gorman'" <mgorman@...hsingularity.net>,
        "'Andrew Morton'" <akpm@...ux-foundation.org>
Cc:     "'Tejun Heo'" <tj@...nel.org>,
        "'Vlastimil Babka'" <vbabka@...e.cz>,
        "'Linux Kernel'" <linux-kernel@...r.kernel.org>,
        "'Linux-MM'" <linux-mm@...ck.org>,
        "'Jesper Dangaard Brouer'" <brouer@...hat.com>
Subject: Re: [PATCH] mm, page_alloc: Use static global work_struct for draining per-cpu pages


On Wednesday, January 25, 2017 4:31 PM Mel Gorman wrote: 
> 
> As suggested by Vlastimil Babka and Tejun Heo, this patch uses a static
> work_struct to co-ordinate the draining of per-cpu pages on the workqueue.
> Only one task can drain at a time but this is better than the previous
> scheme that allowed multiple tasks to send IPIs at a time.
> 
> One consideration is whether parallel requests should synchronise against
> each other. This patch does not synchronise for a global drain as the common
> case for such callers is expected to be multiple parallel direct reclaimers
> competing for pages when the watermark is close to min. Draining the per-cpu
> list is unlikely to make much progress and serialising the drain is of
> dubious merit. Drains are synchonrised for callers such as memory hotplug
> and CMA that care about the drain being complete when the function returns.
> 
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
> ---
Acked-by: Hillf Danton <hillf.zj@...baba-inc.com>