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SubjectRe: [patch] HT scheduler, sched-2.5.59-D7
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On Mon, 2003-01-20 at 13:18, Ingo Molnar wrote:
>
> the attached patch (against 2.5.59) is my current scheduler tree, it
> includes two main areas of changes:
>
> - interactivity improvements, mostly reworked bits from Andrea's tree and
> various tunings.
>
> - HT scheduler: 'shared runqueue' concept plus related logic: HT-aware
> passive load balancing, active-balancing, HT-aware task pickup,
> HT-aware affinity and HT-aware wakeup.

I ran Erich's numatest on a system with this patch, plus the
cputime_stats patch (so that we would get meaningful numbers),
and found a problem. It appears that on the lightly loaded system
sched_best_cpu is now loading up one node before moving on to the
next. Once the system is loaded (i.e., a process per cpu) things
even out. Before applying the D7 patch, processes were distributed
evenly across nodes, even in low load situations.

The numbers below on schedbench show that on 4 and 8 process runs,
the D7 patch gets the same average user time as on the 16 and greater
runs. However, without the D7 patch, the 4 and 8 process runs tend
to have significantly decreased average user time.

Below I'm including the summarized output, and then the detailed
output for the relevant runs on both D7 patched systems and stock.

Overall performance is improved with the D7 patch, so I would like
to find out and fix what went wrong on the light load cases and
encourage the adoption of the the D7 patch (or at least the parts
that make the NUMA scheduler even faster). I'm not likely to have
time to chase this down for the next few days, so am posting
results to see if anyone else can find the cause.

kernels:
* stock59-stats = stock 2.5.59 with the cputime_stats patch
* ingoD7-59.stats = testD7-59 = stock59-stats + Ingo's D7 patch

Kernbench:
Elapsed User System CPU
testD7-59 28.96s 285.314s 79.616s 1260.6%
ingoD7-59.stats 28.824s 284.834s 79.164s 1263.6%
stock59-stats 29.498s 283.976s 83.05s 1243.8%

Schedbench 4:
AvgUser Elapsed TotalUser TotalSys
testD7-59 53.19 53.43 212.81 0.59
ingoD7-59.stats 44.77 46.52 179.10 0.78
stock59-stats 22.25 35.94 89.06 0.81

Schedbench 8:
AvgUser Elapsed TotalUser TotalSys
testD7-59 53.22 53.66 425.81 1.40
ingoD7-59.stats 39.44 47.15 315.62 1.62
stock59-stats 28.40 42.25 227.26 1.67

Schedbench 16:
AvgUser Elapsed TotalUser TotalSys
testD7-59 52.84 58.26 845.49 2.78
ingoD7-59.stats 52.85 57.31 845.68 3.29
stock59-stats 52.97 57.19 847.70 3.29

Schedbench 32:
AvgUser Elapsed TotalUser TotalSys
testD7-59 56.77 122.51 1816.80 7.58
ingoD7-59.stats 56.54 125.79 1809.67 6.97
stock59-stats 56.57 118.05 1810.53 5.97

Schedbench 64:
AvgUser Elapsed TotalUser TotalSys
testD7-59 57.52 234.27 3681.86 18.18
ingoD7-59.stats 58.25 242.61 3728.46 17.40
stock59-stats 56.75 234.12 3632.72 15.70

Detailed stats from running numatest with 4 processes on the D7 patch.
Note how most of the load is put on node 0.

Executing 4 times: ./randupdt 1000000
Running 'hackbench 20' in the background: Time: 5.039
Job node00 node01 node02 node03 | iSched MSched | UserTime(s)
1 100.0 0.0 0.0 0.0 | 0 0 | 46.27
2 58.4 0.0 0.0 41.6 | 0 0 | 41.18
3 100.0 0.0 0.0 0.0 | 0 0 | 45.72
4 100.0 0.0 0.0 0.0 | 0 0 | 45.89
AverageUserTime 44.77 seconds
ElapsedTime 46.52
TotalUserTime 179.10
TotalSysTime 0.78
Detailed stats from running numatest with 8 processes on the D7 patch.
In this one it appears that node 0 was loaded, then node 1.

Executing 8 times: ./randupdt 1000000
Running 'hackbench 20' in the background: Time: 11.185
Job node00 node01 node02 node03 | iSched MSched | UserTime(s)
1 100.0 0.0 0.0 0.0 | 0 0 | 46.89
2 100.0 0.0 0.0 0.0 | 0 0 | 46.20
3 100.0 0.0 0.0 0.0 | 0 0 | 46.31
4 0.0 100.0 0.0 0.0 | 1 1 | 39.44
5 0.0 0.0 99.9 0.0 | 2 2 | 16.00
6 62.6 0.0 0.0 37.4 | 0 0 | 42.23
7 0.0 100.0 0.0 0.0 | 1 1 | 39.12
8 0.0 100.0 0.0 0.0 | 1 1 | 39.35
AverageUserTime 39.44 seconds
ElapsedTime 47.15
TotalUserTime 315.62
TotalSysTime 1.62
Control run - detailed stats running numatest with 4 processes
on a stock59 kernel.

Executing 4 times: ./randupdt 1000000
Running 'hackbench 20' in the background: Time: 8.297
Job node00 node01 node02 node03 | iSched MSched | UserTime(s)
1 0.0 99.8 0.0 0.0 | 1 1 | 16.63
2 100.0 0.0 0.0 0.0 | 0 0 | 27.83
3 0.0 0.0 99.9 0.0 | 2 2 | 16.27
4 100.0 0.0 0.0 0.0 | 0 0 | 28.29
AverageUserTime 22.25 seconds
ElapsedTime 35.94
TotalUserTime 89.06
TotalSysTime 0.81
Control run - detailed stats running numatest with 8 processes
on a stock59 kernel.

Executing 8 times: ./randupdt 1000000
Running 'hackbench 20' in the background: Time: 9.458
Job node00 node01 node02 node03 | iSched MSched | UserTime(s)
1 0.0 99.9 0.0 0.0 | 1 1 | 27.77
2 100.0 0.0 0.0 0.0 | 0 0 | 29.34
3 0.0 0.0 100.0 0.0 | 2 2 | 28.03
4 0.0 0.0 0.0 100.0 | 3 3 | 24.15
5 13.1 0.0 0.0 86.9 | 0 3 *| 33.36
6 0.0 100.0 0.0 0.0 | 1 1 | 27.94
7 0.0 0.0 100.0 0.0 | 2 2 | 28.02
8 100.0 0.0 0.0 0.0 | 0 0 | 28.58
--
Michael Hohnbaum 503-578-5486
hohnbaum@us.ibm.com T/L 775-5486

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