Re: [wake_afine fixes/improvements 0/3] Introduction
From: Paul Turner
Date: Sat Jan 15 2011 - 14:29:59 EST
On Sat, Jan 15, 2011 at 6:29 AM, Mike Galbraith <efault@xxxxxx> wrote:
> On Fri, 2011-01-14 at 17:57 -0800, Paul Turner wrote:
>> I've been looking at the wake_affine path to improve the group scheduling case
>> (wake affine performance for fair group sched has historically lagged) as well
>> as tweaking performance in general.
>>
>> The current series of patches is attached, the first of which should probably be
>> considered for 2.6.38 since it fixes a bug/regression in the case of waking up
>> onto a previously (group) empty cpu. While the others can be considered more
>> forwards looking.
>>
>> I've been using an rpc ping-pong workload which is known be sensitive to poor affine
>> decisions to benchmark these changes, I'm happy to run these patches against
>> other workloads. In particular improvements on reaim have been demonstrated,
>> but since it's not as stable a benchmark the numbers are harder to present in
>> a representative fashion. Suggestions/pet benchmarks greatly appreciated
>> here.
>>
>> Some other things experimented with (but didn't pan out as a performance win):
>> - Considering instantaneous load on prev_cpu as well as current_cpu
>> - Using more gentle wl/wg values to reflect that they a task's contribution to
>> load_contribution is likely less than its weight.
>>
>> Performance:
>>
>> (througput is measured in txn/s across a 5 minute interval, with a 30 second
>> warmup)
>>
>> tip (no group scheduling):
>> throughput=57798.701988 reqs/sec.
>> throughput=58098.876188 reqs/sec.
>>
>> tip: (autogroup + current shares code and associated broken effective_load)
>> throughput=49824.283179 reqs/sec.
>> throughput=48527.942386 reqs/sec.
>>
>> tip (autogroup + old tg_shares code): [parity goal post]
>> throughput=57846.575060 reqs/sec.
>> throughput=57626.442034 reqs/sec.
>>
>> tip (autogroup + effective_load rewrite):
>> throughput=58534.073595 reqs/sec.
>> throughput=58068.072052 reqs/sec.
>>
>> tip (autogroup + effective_load + no affine moves for hot tasks):
>> throughput=60907.794697 reqs/sec.
>> throughput=61208.305629 reqs/sec.
>
> The effective_load() change is a humongous improvement for mysql+oltp.
> The rest is iffy looking on my box with this load.
>
Yes -- this one is definitely the priority, the other is more forward
looking since we've had some good gains with it internally.
> Looks like what will happen with NO_HOT_AFFINE if say two high frequency
> ping pong players are perturbed such that one lands non-affine, it will
> stay that way instead of recovering, because these will always be hot.
> I haven't tested that though, pure rumination ;-)
>
This is a valid concern, the improvements we've seen have been with
many clients. Thinking about it I suspect a better option might be to
just increase the imbalance_pct required for a hot task rather than
blocking the move entirely. Will try this.
> mysql+oltp numbers
>
> unpatched v2.6.37-7185-g52cfd50
>
> clients 1 2 4 8 16 32 64 128 256
> noautogroup 11084.37 20904.39 37356.65 36855.64 35395.45 35585.32 33343.44 28259.58 21404.18
> 11025.94 20870.93 37272.99 36835.54 35367.92 35448.45 33422.20 28309.88 21285.18
> 11076.00 20774.98 36847.44 36881.97 35295.35 35031.19 33490.84 28254.12 21307.13
> 1 avg 11062.10 20850.10 37159.02 36857.71 35352.90 35354.98 33418.82 28274.52 21332.16
>
> autogroup 10963.27 20058.34 23567.63 29361.08 29111.98 29731.23 28563.18 24151.10 18163.00
> 10754.92 19713.71 22983.43 28906.34 28576.12 30809.49 28384.14 24208.99 18057.34
> 10990.27 19645.70 22193.71 29247.07 28763.53 30764.55 28912.45 24143.41 18002.07
> 2 avg 10902.82 19805.91 22914.92 29171.49 28817.21 30435.09 28619.92 24167.83 18074.13
> .985 .949 .616 .791 .815 .860 .856 .854 .847
>
> patched v2.6.37-7185-g52cfd50
>
> noautogroup 11095.73 20794.49 37062.81 36611.92 35444.55 35468.36 33463.56 28236.18 21255.67
> 11035.59 20649.44 37304.91 36878.34 35331.63 35248.05 33424.15 28147.17 21370.39
> 11077.88 20653.92 37207.26 37047.54 35441.78 35445.02 33469.31 28050.80 21306.89
> avg 11069.73 20699.28 37191.66 36845.93 35405.98 35387.14 33452.34 28144.71 21310.98
> vs 1 1.000 .992 1.000 .999 1.001 1.000 1.001 .995 .999
>
> noautogroup 10784.89 20304.49 37482.07 37251.63 35556.21 35116.93 32187.66 27839.60 21023.17
> NO_HOT_AFFINE 10627.17 19835.43 37611.04 37168.37 35609.65 35289.32 32331.95 27598.50 21366.97
> 10378.76 19998.29 37018.31 36888.67 35633.45 35277.39 32300.37 27896.24 21532.09
> avg 10596.94 20046.07 37370.47 37102.89 35599.77 35227.88 32273.32 27778.11 21307.41
> vs 1 .957 .961 1.005 1.006 1.006 .996 .965 .982 .998
>
> autogroup 10452.16 19547.57 36082.97 36653.02 35251.51 34099.80 31226.18 27274.91 20927.65
> 10586.36 19931.37 36928.99 36640.64 35604.17 34238.38 31528.80 27412.44 20874.03
> 10472.72 20143.83 36407.91 36715.85 35481.78 34332.42 31612.57 27357.18 21018.63
> 3 avg 10503.74 19874.25 36473.29 36669.83 35445.82 34223.53 31455.85 27348.17 20940.10
> vs 1 .949 .953 .981 .994 1.002 .967 .941 .967 .981
> vs 2 .963 1.003 1.591 1.257 1.230 1.124 1.099 1.131 1.158
>
> autogroup 10276.41 19642.90 36790.86 36575.28 35326.89 34094.66 31626.82 27185.72 21017.51
> NO_HOT_AFFINE 10305.91 20027.66 37017.90 36814.35 35452.63 34268.32 31399.49 27353.71 21039.37
> 11013.96 19977.08 36984.17 36661.80 35393.99 34141.05 31246.47 26960.48 20873.94
> avg 10532.09 19882.54 36930.97 36683.81 35391.17 34168.01 31424.26 27166.63 20976.94
> vs 1 .952 .953 .993 .995 1.001 .966 .940 .960 .983
> vs 2 .965 1.003 1.611 1.257 1.228 1.122 1.097 1.124 1.160
> vs 3 1.002 1.000 1.012 1.000 .998 .998 .998 .993 1.001
>
>
>
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