linux-kernel - Re: [PATCH v3] mm, sysctl: make NUMA stats configurable

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Date:   Tue, 10 Oct 2017 19:51:43 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     kemi <kemi.wang@...el.com>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Johannes Weiner <hannes@...xchg.org>,
        Christopher Lameter <cl@...ux.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vlastimil Babka <vbabka@...e.cz>,
        Tim Chen <tim.c.chen@...el.com>,
        Andi Kleen <andi.kleen@...el.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Ying Huang <ying.huang@...el.com>,
        Aaron Lu <aaron.lu@...el.com>,
        Proc sysctl <linux-fsdevel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] mm, sysctl: make NUMA stats configurable

On Tue 10-10-17 08:39:47, Dave Hansen wrote:
> On 10/10/2017 07:57 AM, Michal Hocko wrote:
> >> But, let's be honest, this leaves us with an option that nobody is ever
> >> going to turn on.  IOW, nobody except a very small portion of our users
> >> will ever see any benefit from this.
> > But aren't those small groups who would like to squeeze every single
> > cycle out from the page allocator path the targeted audience?
> 
> They're the reason we started looking at this.  They also care the most.
> 
> But, the cost of these stats, especially we get more and more cores in a
> NUMA node is really making them show up in profiles.  It would be nice
> to get rid of them there, too.

I am not opposing to the auto mode. I am just not sure it is a safe
default and I also think that we should add this on top if it is really
needed.
-- 
Michal Hocko
SUSE Labs