Re: [PATCH] sched: Optimize __calc_delta.
From: Peter Zijlstra
Date: Fri Feb 26 2021 - 16:04:09 EST
On Fri, Feb 26, 2021 at 11:52:39AM -0800, Josh Don wrote:
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From: Clement Courbet <courbet@xxxxxxxxxx>
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A significant portion of __calc_delta time is spent in the loop
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shifting a u64 by 32 bits. Use a __builtin_clz instead of iterating.
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This is ~7x faster on benchmarks.
Have you tried on hardware without such fancy instructions?