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On Nov 28, 2011 11:32 AM, "Michael Mol" <mikemol@×××××.com> wrote: |
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----- >8 snip |
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> MAKEOPTS would be -j16, -l10. (Which actually goes up to about 12 or |
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> 13 based on that N*1.6 behavior) |
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----- >8 snip |
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Just in case anyone wonders where the multiplier "1.6" comes from: |
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There had been a discussion somewhere (I forgot where exactly, sorry) about |
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load numbers. The final conclusion was that the ideal load number for |
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today's processors is 2*N, because with the out-of-order capability of |
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modern processors, two instructions can overlap in the pipeline, even |
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without hyperthreading. |
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Unfortunately, striving for 2*N will inadvertently result in short bursts |
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of > 2*N, and this potentially induce a stall, which will be very costly. |
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1.8*N gives a 10% margin for burst activities, while 1.6*N gives a 20% |
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margin. |
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Since emerging packages has a sudden increase in load when autoconfigure |
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finishes and make fires up all the parallel building, I figure 20% margin |
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will be better. |
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Of course, that's before @mikemol made me aware of MAKEOPTS -l, so I am now |
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tempted to raise the load-average to 1.8*N, letting make handle the bursts. |
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Rgds, |
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