Messages in this thread | | | Subject | Re: [PATCH v3 0/4] x86/fpu: Reduce unnecessary FNINIT and MXCSR usage | From | Krzysztof Olędzki <> | Date | Thu, 21 Jan 2021 01:29:23 -0800 |
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On 2021-01-20 at 21:09, Andy Lutomirski wrote: > This series fixes two regressions: a boot failure on AMD K7 and a > performance regression on everything. > > I did a double-take here -- the regressions were reported by different > people, both named Krzysztof :) > > Changes from v2: > - Tidy up the if statements (Sean) > - Changelog and comment improvements (Boris) > > Changes from v1: > - Fix MMX better -- MMX really does need FNINIT. > - Improve the EFI code. > - Rename the KFPU constants. > - Changelog improvements. > > Andy Lutomirski (4): > x86/fpu: Add kernel_fpu_begin_mask() to selectively initialize state > x86/mmx: Use KFPU_387 for MMX string operations > x86/fpu: Make the EFI FPU calling convention explicit > x86/fpu/64: Don't FNINIT in kernel_fpu_begin()
Hi Andy,
I have tested the new patchset on the following CPUs running 5.4.90 (with some adjustments required for it to apply) and 5.10.9 kernels: - AMD Phenom(tm) II X3 B77 Processor (family: 0x10, model: 0x4, stepping: 0x3) - Intel(R) Xeon(R) CPU 3070 @ 2.66GHz (family: 0x6, model: 0xf, stepping: 0x6) - Intel(R) Xeon(R) CPU E3-1280 V2 @ 3.60GHz (family: 0x6, model: 0x3a, stepping: 0x9)
For all of them, it was possible to recover most of the performance lost due to the introduction of "Reset MXCSR to default in kernel_fpu_begin": - B77: 90% instead of 82% for prefetch64-sse, 92% instead of 84% for generic_sse - 3070: 93% instead of 86% for prefetch64-sse, 93% instead of 88% for generic_sse - 1280v2: 99% instead of 88% for prefetch64-sse, 99% instead of 88% for generic_sse.
For some reason, 1280v2 (Ivy Bridge) sees almost no regression for prefetch64-sse and generic_sse. The only issue is that AVX is still at 67% of its original performance. This is of course better compared to 60%. There is no AVX on the other 2 CPUs.
I was using 64 bit kernels for testing, please let me know if 32 bit is also needed.
Tested-by: Krzysztof Piotr Olędzki <ole@ans.pl>
Thanks, Krzysztof
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