linux-kernel - Re: [RFC] syscall calling convention, stts/clts, and xstate latency

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Date:	Mon, 25 Jul 2011 13:04:46 +0200
From:	Hans Rosenfeld <hans.rosenfeld@....com>
To:	Andrew Lutomirski <luto@....edu>
CC:	Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	x86 <x86@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Avi Kivity <avi@...hat.com>
Subject: Re: [RFC] syscall calling convention, stts/clts, and xstate latency

On Mon, Jul 25, 2011 at 05:44:32AM -0400, Andrew Lutomirski wrote:
> On Mon, Jul 25, 2011 at 2:38 AM, Ingo Molnar <mingo@...e.hu> wrote:
> > I should have mentioned it earlier, but there's a certain amount of
> > delazying patches in the tip:x86/xsave branch:
> >
> >  $ gll linus..x86/xsave
> >  300c6120b465: x86, xsave: fix non-lazy allocation of the xsave area
> >  f79018f2daa9: Merge branch 'x86/urgent' into x86/xsave
> >  66beba27e8b5: x86, xsave: remove lazy allocation of xstate area
> >  1039b306b1c6: x86, xsave: add kernel support for AMDs Lightweight Profiling (LWP)
> >  4182a4d68bac: x86, xsave: add support for non-lazy xstates
> >  324cbb83e215: x86, xsave: more cleanups
> >  2efd67935eb7: x86, xsave: remove unused code
> >  0c11e6f1aed1: x86, xsave: cleanup fpu/xsave signal frame setup
> >  7f4f0a56a7d3: x86, xsave: rework fpu/xsave support
> >  26bce4e4c56f: x86, xsave: cleanup fpu/xsave support
> >
> > it's not in tip:master because the LWP bits need (much) more work to
> > be palatable - but we could spin them off and complete them as per
> > your suggestions if they are an independent speedup on modern CPUs.
> 
> Hans, what's the status of these?  I want to do some other cleanups
> (now or in a couple of weeks) that will probably conflict with your
> xsave work.

I know of one bug in there that occasionally causes panics at boot, see
the attached patch for a fix.


Hans


-- 
%SYSTEM-F-ANARCHISM, The operating system has been overthrown

View attachment "0001-x86-xsave-clear-pre-allocated-xsave-area.patch" of type "text/plain" (1057 bytes)