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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id x65-v6sm17020833wmg.39.2018.09.10.01.39.26 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 10 Sep 2018 01:39:27 -0700 (PDT) Date: Mon, 10 Sep 2018 10:39:25 +0200 From: Ingo Molnar To: Srikar Dronamraju Cc: Peter Zijlstra , LKML , Mel Gorman , Rik van Riel , Thomas Gleixner Subject: Re: [PATCH 2/6] mm/migrate: Use trylock while resetting rate limit Message-ID: <20180910083925.GB48257@gmail.com> References: <1533276841-16341-1-git-send-email-srikar@linux.vnet.ibm.com> <1533276841-16341-3-git-send-email-srikar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1533276841-16341-3-git-send-email-srikar@linux.vnet.ibm.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Srikar Dronamraju wrote: > Since this spinlock will only serialize migrate rate limiting, > convert the spinlock to a trylock. If another task races ahead of this task > then this task can simply move on. > > While here, add correct two abnormalities. > - Avoid time being stretched for every interval. > - Use READ/WRITE_ONCE with next window. > > specjbb2005 / bops/JVM / higher bops are better > on 2 Socket/2 Node Intel > JVMS Prev Current %Change > 4 206350 200892 -2.64502 > 1 319963 325766 1.81365 > > > on 2 Socket/2 Node Power9 (PowerNV) > JVMS Prev Current %Change > 4 186539 190261 1.99529 > 1 220344 195305 -11.3636 > > > on 4 Socket/4 Node Power7 > JVMS Prev Current %Change > 8 56836 57651.1 1.43413 > 1 112970 111351 -1.43312 > > > dbench / transactions / higher numbers are better > on 2 Socket/2 Node Intel > count Min Max Avg Variance %Change > 5 13136.1 13170.2 13150.2 14.7482 > 5 12254.7 12331.9 12297.8 28.1846 -6.48203 > > > on 2 Socket/4 Node Power8 (PowerNV) > count Min Max Avg Variance %Change > 5 4319.79 4998.19 4836.53 261.109 > 5 4997.83 5030.14 5015.54 12.947 3.70121 > > > on 2 Socket/2 Node Power9 (PowerNV) > count Min Max Avg Variance %Change > 5 9325.56 9402.7 9362.49 25.9638 > 5 9331.84 9375.11 9352.04 16.0703 -0.111616 > > > on 4 Socket/4 Node Power7 > count Min Max Avg Variance %Change > 5 132.581 191.072 170.554 21.6444 > 5 147.55 181.605 168.963 11.3513 -0.932842 Firstly, *please* always characterize benchmark runs. What did you find? How should we interpret the result? Are there any tradeoffs? *Don't* just dump them on us. Because in this particular case the results are not obvious, at all: > specjbb2005 / bops/JVM / higher bops are better > on 2 Socket/2 Node Intel > JVMS Prev Current %Change > 4 206350 200892 -2.64502 > 1 319963 325766 1.81365 > > > on 2 Socket/2 Node Power9 (PowerNV) > JVMS Prev Current %Change > 4 186539 190261 1.99529 > 1 220344 195305 -11.3636 > > > on 4 Socket/4 Node Power7 > JVMS Prev Current %Change > 8 56836 57651.1 1.43413 > 1 112970 111351 -1.43312 Why is this better? The largest drop is 11% which seems significant. Thanks, Ingo