Re: [BENCHMARK] max bomb segment tuning with read latency 2 patch in contest

Con Kolivas
2002-12-07T13:20:02Z

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>Here are some io_load contest benchmarks with 2.4.20 with the read latency2
>patch applied and varying the max bomb segments from 1-6 (SMP used to save
>time!)
>
>io_load:
>Kernel [runs] Time CPU% Loads LCPU% Ratio
>2.4.20 [5] 164.9 45 31 21 4.55
>2420rl2b1 [5] 93.5 81 18 22 2.58
>2420rl2b2 [5] 88.2 87 16 22 2.44
>2420rl2b4 [5] 87.8 84 17 22 2.42
>2420rl2b6 [5] 100.3 77 19 22 2.77
>
>io_other:
>Kernel [runs] Time CPU% Loads LCPU% Ratio
>2.4.20 [5] 89.6 86 17 21 2.47
>2420rl2b1 [3] 48.1 156 9 21 1.33
>2420rl2b2 [3] 50.0 149 9 21 1.38
>2420rl2b4 [5] 51.9 141 10 21 1.43
>2420rl2b6 [5] 52.1 142 9 20 1.44
>
>There seems to be a limit to the benefit of decreasing max bomb segments. It
>does not seem to have a significant effect on io load on another hard disk
>(although read latency2 is overall much better than vanilla).
>
>Con

Further testing with changing values of read and write latencies (with fixed
max_bomb to 4) and the read latency 2 patch in place shows no significant
change to these figures over a wide range of numbers. This was not the case
when I ran contest with different read latency values on the vanilla kernel
(and found -r 512 to be a reasonable compromise according to Jens). Is there
some other advantage to be gained by say increasing these numbers? (since
contest results don't change with higher numbers either)

Con
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