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Simon Marlow authored
The clearNurseries() operation resets the free pointer in each nursery block to the start of the block, emptying the nursery. In the parallel GC this was done on the main GC thread, but that's bad because it accesses the bdescr of every nursery block, and move all those cache lines onto the CPU of the main GC thread. With large nurseries, this can be especially bad. So instead we want to clear each nursery in its local GC thread. Thanks to Andreas Voellmy <andreas.voellmy@gmail.com> for idenitfying the issue. After this change and the previous patch to make the last GC a major one, I see these results for nofib/parallel on 8 cores: blackscholes +0.0% +0.0% -3.7% -3.3% +0.3% coins +0.0% +0.0% -5.1% -5.0% +0.4% gray +0.0% +0.0% -4.5% -2.1% +0.8% mandel +0.0% -0.0% -7.6% -5.1% -2.3% matmult +0.0% +5.5% -2.8% -1.9% -5.8% minimax +0.0% +0.0% -10.6% -10.5% +0.0% nbody +0.0% -4.4% +0.0% 0.07 +0.0% parfib +0.0% +1.0% +0.5% +0.9% +0.0% partree +0.0% +0.0% -2.4% -2.5% +1.7% prsa +0.0% -0.2% +1.8% +4.2% +0.0% queens +0.0% -0.0% -1.8% -1.4% -4.8% ray +0.0% -0.6% -18.5% -17.8% +0.0% sumeuler +0.0% -0.0% -3.7% -3.7% +0.0% transclos +0.0% -0.0% -25.7% -26.6% +0.0% -------------------------------------------------------------------------------- Min +0.0% -4.4% -25.7% -26.6% -5.8% Max +0.0% +5.5% +1.8% +4.2% +1.7% Geometric Mean +0.0% +0.1% -6.3% -6.1% -0.7%
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