Add a prefetch buffer in front of the GC stack #49430
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vtjnash
reviewed
Apr 20, 2023
| if (push_into_queue) { | ||
| __builtin_prefetch(jl_astaggedvalue(new_obj), 1, 3); | ||
| __builtin_prefetch(&((jl_value_t**)new_obj)[7], 1, 3); | ||
| __builtin_prefetch(&((jl_value_t**)new_obj)[16], 1, 3); |
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128 bytes after the header seems a bit unlikely to need? Is the assumption that gets the full cache line around it?
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This is a prototype implementation, it shows decent speedups on Intel and AMD machines, but on the M1 it's less clear, the sweep prefetching seems to be a win everywhere.
It seems the M1 hardware prefetch is already smart enough so it does it by default.