| Date | Tue, 13 Jan 2015 18:11:34 +0100 | From | Oleg Nesterov <> | Subject | Re: [RFC PATCH 04/11] x86,fpu: defer FPU restore until return to userspace |
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On 01/11, riel@redhat.com wrote: > > Defer restoring the FPU state, if so desired, until the task returns to > userspace.
And I have another concern.
Afaocs with this patch the idle threads will run with TIF_LOAD_FPU set but without fpu.has_fpu.
This is fine by itself, but this (performance-wise) breaks kernel_fpu_begin() if use_eager_fpu() == T. Please see the changelog in 5187b28ff08249ab8a162e8 and note that this patch cc's @stable.
Yes, yes, even if I am right we should blame kernel_fpu_begin() and other eager_fpu oddities. I tried to start the cleanups/fixes in this area some time ago, but they were ignored.
Oleg.
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