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SubjectRe: NUMA scheduler (was: 2.5 merge candidate list 1.5)
Date
On Monday 28 October 2002 01:46, Martin J. Bligh wrote:
> Erich, what does all the pool stuff actually buy us over what
> Michael is doing? Seems to be rather more complex, but maybe
> it's useful for something we're just not measuring here?

The more complicated stuff is for achieving equal load between the
nodes. It delays steals more when the stealing node is averagely loaded,
less when it is unloaded. This is the place where we can make it cope
with more complex machines with multiple levels of memory hierarchy
(like our 32 CPU TX7). Equal load among the nodes is important if you
have memory bandwidth eaters, as the bandwidth in a node is limited.

When introducing node affinity (which shows good results for me!) you
also need a more careful ranking of the tasks which are candidates to
be stolen. The routine task_to_steal does this and is another source
of complexity. It is another point where the multilevel stuff comes in.
In the core part of the patch the rank of the steal candidates is computed
by only taking into account the time which a task has slept.

I attach the script for getting some statistics on the numa_test. I
consider this test more sensitive to NUMA effects, as it is a bandwidth
eater also needing good latency.
(BTW, Martin: in the numa_test script I've sent you the PROBLEMSIZE must
be set to 1000000!).
Regards,
Erich


>
> 2.5.44-mm4 Virgin
> 2.5.44-mm4-focht-1 Focht main
> 2.5.44-mm4-hbaum-1 Hbaum main
> 2.5.44-mm4-focht-12 Focht main + Focht balance_exec
> 2.5.44-mm4-hbaum-1 Hbaum main + Hbaum balance_exec
> 2.5.44-mm4-f1-h2 Focht main + Hbaum balance_exec
>
> Kernbench:
> Elapsed User System CPU
> 2.5.44-mm4 19.676s 192.794s 42.678s 1197.4%
> 2.5.44-mm4-focht-1 19.46s 189.838s 37.938s 1171%
> 2.5.44-mm4-hbaum-1 19.746s 189.232s 38.354s 1152.2%
> 2.5.44-mm4-focht-12 20.32s 190s 44.4s 1153.6%
> 2.5.44-mm4-hbaum-12 19.322s 190.176s 40.354s 1192.6%
> 2.5.44-mm4-f1-h2 19.398s 190.118s 40.06s 1186%
>
> Schedbench 4:
> Elapsed TotalUser TotalSys AvgUser
> 2.5.44-mm4 32.45 49.47 129.86 0.82
> 2.5.44-mm4-focht-1 38.61 45.15 154.48 1.06
> 2.5.44-mm4-hbaum-1 37.81 46.44 151.26 0.78
> 2.5.44-mm4-focht-12 23.23 38.87 92.99 0.85
> 2.5.44-mm4-hbaum-12 22.26 34.70 89.09 0.70
> 2.5.44-mm4-f1-h2 21.39 35.97 85.57 0.81
>
> Schedbench 8:
> Elapsed TotalUser TotalSys AvgUser
> 2.5.44-mm4 39.90 61.48 319.26 2.79
> 2.5.44-mm4-focht-1 37.76 61.09 302.17 2.55
> 2.5.44-mm4-hbaum-1 43.18 56.74 345.54 1.71
> 2.5.44-mm4-focht-12 28.40 34.43 227.25 2.09
> 2.5.44-mm4-hbaum-12 30.71 45.87 245.75 1.43
> 2.5.44-mm4-f1-h2 36.11 45.18 288.98 2.10
>
> Schedbench 16:
> Elapsed TotalUser TotalSys AvgUser
> 2.5.44-mm4 62.99 93.59 1008.01 5.11
> 2.5.44-mm4-focht-1 51.69 60.23 827.20 4.95
> 2.5.44-mm4-hbaum-1 52.57 61.54 841.38 3.93
> 2.5.44-mm4-focht-12 51.24 60.86 820.08 4.23
> 2.5.44-mm4-hbaum-12 52.33 62.23 837.46 3.84
> 2.5.44-mm4-f1-h2 51.76 60.15 828.33 5.67
>
> Schedbench 32:
> Elapsed TotalUser TotalSys AvgUser
> 2.5.44-mm4 88.13 194.53 2820.54 11.52
> 2.5.44-mm4-focht-1 56.71 123.62 1815.12 7.92
> 2.5.44-mm4-hbaum-1 54.57 153.56 1746.45 9.20
> 2.5.44-mm4-focht-12 55.69 118.85 1782.25 7.28
> 2.5.44-mm4-hbaum-12 54.36 135.30 1739.95 8.09
> 2.5.44-mm4-f1-h2 55.97 119.28 1791.39 7.20
>
> Schedbench 64:
> Elapsed TotalUser TotalSys AvgUser
> 2.5.44-mm4 159.92 653.79 10235.93 25.16
> 2.5.44-mm4-focht-1 55.60 232.36 3558.98 17.61
> 2.5.44-mm4-hbaum-1 71.48 361.77 4575.45 18.53
> 2.5.44-mm4-focht-12 56.03 234.45 3586.46 15.76
> 2.5.44-mm4-hbaum-12 56.91 240.89 3642.99 15.67
> 2.5.44-mm4-f1-h2 56.48 246.93 3615.32 16.97
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