linux-kernel - Re: [RFC 02/10] autonuma: Reduce cache footprint when scanning page tables

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Date:   Fri, 1 Nov 2019 11:13:08 +0000
From:   Mel Gorman <mgorman@...e.de>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>, Rik van Riel <riel@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [RFC 02/10] autonuma: Reduce cache footprint when scanning page
 tables

On Fri, Nov 01, 2019 at 03:57:19PM +0800, Huang, Ying wrote:
> From: Huang Ying <ying.huang@...el.com>
> 
> In auto NUMA balancing page table scanning, if the pte_protnone() is
> true, the PTE needs not to be changed because it's in target state
> already.  So other checking on corresponding struct page is
> unnecessary too.
> 
> So, if we check pte_protnone() firstly for each PTE, we can avoid
> unnecessary struct page accessing, so that reduce the cache footprint
> of NUMA balancing page table scanning.
> 
> In the performance test of pmbench memory accessing benchmark with
> 80:20 read/write ratio and normal access address distribution on a 2
> socket Intel server with Optance DC Persistent Memory, perf profiling
> shows that the autonuma page table scanning time reduces from 1.23% to
> 0.97% (that is, reduced 21%) with the patch.
> 
> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>

Acked-by: Mel Gorman <mgorman@...e.de>

This patch is independent of the series and should be resent separately.
Alternatively Andrew, please pick this patch up on its own.

-- 
Mel Gorman
SUSE Labs