linux-kernel - [PATCH 0/3] x86, fpu: kernel_fpu

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Message-ID: <20150115191918.GA27332@redhat.com>
Date:	Thu, 15 Jan 2015 20:19:18 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Rik van Riel <riel@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Suresh Siddha <sbsiddha@...il.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...hat.com, hpa@...or.com,
	matt.fleming@...el.com, bp@...e.de, pbonzini@...hat.com,
	tglx@...utronix.de, luto@...capital.net
Subject: [PATCH 0/3] x86, fpu: kernel_fpu_begin/end initial cleanups/fix

Add cc's.

On 01/11, riel@...hat.com wrote:
>
> Currently the kernel will always load the FPU context, even
> when switching to a kernel thread, or to an idle thread. In
> the case of a task on a KVM VCPU going idle for a bit, and
> waking up again later, this creates a vastly inefficient
> chain of FPU context saves & loads:

I assume you will send v2.

Let me send initial kernel_fpu_begin/end cleanups, I believe they make
sense anyway and won't conflict with your changes.

This is actually resend, I sent more patches some time ago but they were
ignored.

Note that (I hope) we can do more changes on top of this series, in
particular:

	- remove all checks from irq_fpu_usable() except in_kernel_fpu

	- do not abuse FPU in kernel threads, this makes sense even if
	  use_eager_fpu(), and with or without the changes you proposed.

Please review.

Oleg.

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