linux-kernel - Re: [RFC PATCH v2 0/4] Eliminate zone->lock contention for will-it-scale/page

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Message-ID: <2606b76f-be64-4cef-b1f7-055732d09251@oracle.com>
Date:   Thu, 29 Mar 2018 15:19:46 -0400
From:   Daniel Jordan <daniel.m.jordan@...cle.com>
To:     Aaron Lu <aaron.lu@...el.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Huang Ying <ying.huang@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Kemi Wang <kemi.wang@...el.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [RFC PATCH v2 0/4] Eliminate zone->lock contention for
 will-it-scale/page_fault1 and parallel free

On 03/20/2018 04:54 AM, Aaron Lu wrote:
> This series is meant to improve zone->lock scalability for order 0 pages.
> With will-it-scale/page_fault1 workload, on a 2 sockets Intel Skylake
> server with 112 CPUs, CPU spend 80% of its time spinning on zone->lock.
> Perf profile shows the most time consuming part under zone->lock is the
> cache miss on "struct page", so here I'm trying to avoid those cache
> misses.

I ran page_fault1 comparing 4.16-rc5 to your recent work, these four 
patches plus the three others from your github branch zone_lock_rfc_v2. 
Out of curiosity I also threw in another 4.16-rc5 with the pcp batch 
size adjusted so high (10922 pages) that we always stay in the pcp lists 
and out of buddy completely.  I used your patch[*] in this last kernel.

This was on a 2-socket, 20-core broadwell server.

There were some small regressions a bit outside the noise at low process 
counts (2-5) but I'm not sure they're repeatable.  Anyway, it does 
improve the microbenchmark across the board.

[*] lkml.kernel.org/r/20170919072342.GB7263 () intel ! com


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