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Date: Wed, 16 Jun 2010 10:24:18 +0300 From: Avi Kivity <avi@...hat.com> To: Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com> CC: kvm@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 0/4] Really lazy fpu On 06/13/2010 06:03 PM, Avi Kivity wrote: > Currently fpu management is only lazy in one direction. When we switch into > a task, we may avoid loading the fpu state in the hope that the task will > never use it. If we guess right we save an fpu load/save cycle; if not, > a Device not Available exception will remind us to load the fpu. > > However, in the other direction, fpu management is eager. When we switch out > of an fpu-using task, we always save its fpu state. > > This is wasteful if the task(s) that run until we switch back in all don't use > the fpu, since we could have kept the task's fpu on the cpu all this time > and saved an fpu save/load cycle. This can be quite common with threaded > interrupts, but will also happen with normal kernel threads and even normal > user tasks. > > This patch series converts task fpu management to be fully lazy. When > switching out of a task, we keep its fpu state on the cpu, only flushing it > if some other task needs the fpu. > Ingo, Peter, any feedback on this? -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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