linux-kernel - Re: [PATCH v2 3/5] mm: use a dedicated workqueue for the free workers

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Message-ID: <4549498a-befc-133d-b204-dd69b191e579@intel.com>
Date:   Thu, 23 Mar 2017 08:38:43 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Aaron Lu <aaron.lu@...el.com>, Minchan Kim <minchan@...nel.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Tim Chen <tim.c.chen@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ying Huang <ying.huang@...el.com>
Subject: Re: [PATCH v2 3/5] mm: use a dedicated workqueue for the free workers

On 03/22/2017 01:41 AM, Aaron Lu wrote:
> On Wed, Mar 22, 2017 at 03:33:35PM +0900, Minchan Kim wrote:
>> On Wed, Mar 15, 2017 at 05:00:02PM +0800, Aaron Lu wrote:
>>> Introduce a workqueue for all the free workers so that user can fine
>>> tune how many workers can be active through sysfs interface: max_active.
>>> More workers will normally lead to better performance, but too many can
>>> cause severe lock contention.
>>
>> Let me ask a question.
>>
>> How well can workqueue distribute the jobs in multiple CPU?
> 
> I would say it's good enough for my needs.
> After all, it doesn't need many kworkers to achieve the 50% time
> decrease: 2-4 kworkers for EP and 4-8 kworkers for EX are enough from
> previous attched data.

It's also worth noting that we'd like to *also* like to look into
increasing how scalable freeing pages to a given zone is.