Messages in this thread | | | Date | Sun, 10 Nov 2002 11:09:42 +0100 | From | Jens Axboe <> | Subject | Re: [BENCHMARK] 2.4.{18,19{-ck9},20rc1{-aa1}} with contest |
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On Sun, Nov 10 2002, Con Kolivas wrote: > >The default is 2048. How long does the io_load test take, or rather how > >many tests are appropriate to do? To get a good picture of how it looks > >you should probably try: 0, 8, 16, 64, 128, 512. Once you get some of > >these results, it will be easier to determine which area(s) would be > >most interesting to further explore. > > The io_load test takes as long as the time in seconds shown on the table. At > least 3 tests are appropriate to get a reasonable average [runs is in square > parentheses]. Therefore it takes about half an hour per run. Luckily I had > the benefit of a night to set up a whole lot of runs: > > io_load: > Kernel [runs] Time CPU% Loads LCPU% Ratio > 2420rc1r0 [3] 489.3 15 36 10 6.85 > 2420rc1r8 [3] 485.5 15 35 10 6.80 > 2420rc1r16 [3] 570.4 12 43 10 7.99 > 2420rc1r32 [3] 570.1 12 42 10 7.98 > 2420rc1r64 [3] 575.0 12 43 10 8.05 > 2420rc1r128 [3] 611.4 11 46 10 8.56 > 2420rc1r256 [3] 646.2 11 49 10 9.05 > 2420rc1r512 [3] 603.7 12 45 10 8.46 > 2420rc1r1024 [3] 693.9 10 53 10 9.72 > 2.4.20-rc1 [2] 1142.2 6 90 10 16.00 > > Test hardware is 1133Mhz P3 laptop with 5400rpm ATA100 drive. I don't doubt > the response curve would be different for other hardware.
That looks pretty good, the behaviour in 2.4.20-rc1 is no sanely tunable unlike before. Could you retest the whole contest suite with 512 as the default value? It looks like a good default for 2.4.20.
Marcelo, we probably need to make few tweaks here to get the read passover value right. The algorithmic changes in 2.4.20-pre made it impossible to guess a good default value, as we invalidated the previous tests. Right now we are using 2048 which is a number I basically pulled out of my ass, it looks as if it might be a bit high. So I'll be sending you a one-liner correction once a decent default value is found.
-- Jens Axboe
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