Messages in this thread | | | Date | Thu, 21 Jun 2018 10:51:12 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH v2 13/19] mm/migrate: Use xchg instead of spinlock |
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On Wed, Jun 20, 2018 at 10:32:54PM +0530, Srikar Dronamraju wrote: > Currently resetting the migrate rate limit is under a spinlock. > The spinlock will only serialize the migrate rate limiting and something > similar can actually be achieved by a simpler xchg. > > Running SPECjbb2005 on a 4 node machine and comparing bops/JVM > JVMS LAST_PATCH WITH_PATCH %CHANGE > 16 25804.1 25355.9 -1.73 > 1 73413 72812 -0.81 > > Running SPECjbb2005 on a 16 node machine and comparing bops/JVM > JVMS LAST_PATCH WITH_PATCH %CHANGE > 8 101748 110199 8.30 > 1 170818 176303 3.21 > > (numbers from v1 based on v4.17-rc5) > Testcase Time: Min Max Avg StdDev > numa01.sh Real: 435.67 707.28 527.49 97.85 > numa01.sh Sys: 76.41 231.19 162.49 56.13 > numa01.sh User: 38247.36 59033.52 45129.31 7642.69 > numa02.sh Real: 60.35 62.09 61.09 0.69 > numa02.sh Sys: 15.01 30.20 20.64 5.56 > numa02.sh User: 5195.93 5294.82 5240.99 40.55 > numa03.sh Real: 752.04 919.89 836.81 63.29 > numa03.sh Sys: 115.10 133.35 125.46 7.78 > numa03.sh User: 58736.44 70084.26 65103.67 4416.10 > numa04.sh Real: 418.43 709.69 512.53 104.17 > numa04.sh Sys: 242.99 370.47 297.39 42.20 > numa04.sh User: 34916.14 48429.54 38955.65 4928.05 > numa05.sh Real: 379.27 434.05 403.70 17.79 > numa05.sh Sys: 145.94 344.50 268.72 68.53 > numa05.sh User: 32679.32 35449.75 33989.10 913.19 > > Testcase Time: Min Max Avg StdDev %Change > numa01.sh Real: 490.04 774.86 596.26 96.46 -11.5% > numa01.sh Sys: 151.52 242.88 184.82 31.71 -12.0% > numa01.sh User: 41418.41 60844.59 48776.09 6564.27 -7.47% > numa02.sh Real: 60.14 62.94 60.98 1.00 0.180% > numa02.sh Sys: 16.11 30.77 21.20 5.28 -2.64% > numa02.sh User: 5184.33 5311.09 5228.50 44.24 0.238% > numa03.sh Real: 790.95 856.35 826.41 24.11 1.258% > numa03.sh Sys: 114.93 118.85 117.05 1.63 7.184% > numa03.sh User: 60990.99 64959.28 63470.43 1415.44 2.573% > numa04.sh Real: 434.37 597.92 504.87 59.70 1.517% > numa04.sh Sys: 237.63 397.40 289.74 55.98 2.640% > numa04.sh User: 34854.87 41121.83 38572.52 2615.84 0.993% > numa05.sh Real: 386.77 448.90 417.22 22.79 -3.24% > numa05.sh Sys: 149.23 379.95 303.04 79.55 -11.3% > numa05.sh User: 32951.76 35959.58 34562.18 1034.05 -1.65% > > Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
However, I'm actively considering removing rate limiting entirely. It has been reported elsewhere that it was a limiting factor for some workloads. When it was introduced, it was to avoid worst-case migration storms but I believe that those ping-pong style problems should now be ok.
-- Mel Gorman SUSE Labs
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