Messages in this thread | | | Subject | Re: [PATCH v4 1/2] x86/fpu: track AVX-512 usage of tasks | From | Dave Hansen <> | Date | Tue, 11 Dec 2018 09:18:25 -0800 |
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On 12/10/18 4:24 PM, Aubrey Li wrote: > The tracking turns on the usage flag at the next context switch of > the task, but requires 3 consecutive context switches with no usage > to clear it. This decay is required because well-written AVX-512 > applications are expected to clear this state when not actively using > AVX-512 registers.
One concern about this: Given a HZ=1000 system, this means that the flag needs to get scanned every ~3ms. That's a pretty good amount of scanning on a system with hundreds or thousands of tasks running around.
How many tasks does this scale to until you're eating up an entire CPU or two just scanning /proc?
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