Messages in this thread | | | Date | Mon, 07 Oct 2002 00:38:20 -0700 | From | Andrew Morton <> | Subject | Re: [BENCHMARK] 2.5.40-mm2 with contest |
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Con Kolivas wrote: > > > Here are the latest results including 2.5.40-mm2 with contest v0.50 > (http://contest.kolivas.net) > > ... > > mem_load: > Kernel [runs] Time CPU% Loads LCPU% Ratio > 2.4.19 [3] 100.0 72 33 3 1.49 > 2.5.38 [3] 107.3 70 34 3 1.60 > 2.5.39 [2] 103.1 72 31 3 1.53 > 2.5.40 [2] 102.5 72 31 3 1.53 > 2.5.40-mm1 [2] 107.7 68 29 2 1.60 > 2.5.40-mm2 [2] 165.1 44 38 2 2.46 >
-mm2 has the "don't swap so much" knob. By default it is set at 50%. The VM _wants_ to reclaim lots of memory from mem_load so that gcc has some cache to chew on. But you the operator have said "I know better and I don't want you to do that".
Because it is prevented from building enough cache, gcc is issuing a ton of reads, which are hampering the swapstorm which is happening at the other end of the disk. It's a lose-lose.
There's not much that can be done about that really (apart from some heavy-handed load control) - if you want to optimise for throughput above all else,
echo 100 > /proc/sys/vm/swappiness
(I suspect our swap performance right now is fairly poor, in terms of block allocation, readaround, etc. Nobody has looked at that in some time afaik. But tuning in there is unlikely to make a huge difference). - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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