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From:   "Wang, Kemi" <kemi.wang@intel.com>
To:     Michal Hocko <mhocko@kernel.org>
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Subject: RE: [PATCH 1/2] mm: NUMA stats code cleanup and enhancement
Thread-Topic: [PATCH 1/2] mm: NUMA stats code cleanup and enhancement
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Date:   Thu, 30 Nov 2017 11:06:51 +0000
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Of course, we should do that AFAP. Thanks for your comments :)

-----Original Message-----
From: owner-linux-mm@kvack.org [mailto:owner-linux-mm@kvack.org] On Behalf Of Michal Hocko
Sent: Thursday, November 30, 2017 5:45 PM
To: Wang, Kemi <kemi.wang@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Andrew Morton <akpm@linux-foundation.org>; Vlastimil Babka <vbabka@suse.cz>; Mel Gorman <mgorman@techsingularity.net>; Johannes Weiner <hannes@cmpxchg.org>; Christopher Lameter <cl@linux.com>; YASUAKI ISHIMATSU <yasu.isimatu@gmail.com>; Andrey Ryabinin <aryabinin@virtuozzo.com>; Nikolay Borisov <nborisov@suse.com>; Pavel Tatashin <pasha.tatashin@oracle.com>; David Rientjes <rientjes@google.com>; Sebastian Andrzej Siewior <bigeasy@linutronix.de>; Dave <dave.hansen@linux.intel.com>; Kleen, Andi <andi.kleen@intel.com>; Chen, Tim C <tim.c.chen@intel.com>; Jesper Dangaard Brouer <brouer@redhat.com>; Huang, Ying <ying.huang@intel.com>; Lu, Aaron <aaron.lu@intel.com>; Li, Aubrey <aubrey.li@intel.com>; Linux MM <linux-mm@kvack.org>; Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] mm: NUMA stats code cleanup and enhancement

On Thu 30-11-17 17:32:08, kemi wrote:
[...]
> Your patch saves more code than mine because the node stats framework 
> is reused for numa stats. But it has a performance regression because 
> of the limitation of threshold size (125 at most, see 
> calculate_normal_threshold() in vmstat.c) in inc_node_state().

But this "regression" would be visible only on those workloads which really need to squeeze every single cycle out of the allocation hot path and those are supposed to disable the accounting altogether. Or is this visible on a wider variety of workloads.

Do not get me wrong. If we want to make per-node stats more optimal, then by all means let's do that. But having 3 sets of counters is just way to much.

--
Michal Hocko
SUSE Labs

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