Re: [wake_afine fixes/improvements 0/3] Introduction

[Mike Galbraith]

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.

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 ;-)

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


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/