linux-kernel - Re: Re-tune x86 uaccess code for PREEMPT

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Message-ID: <1376114128.5332.17.camel@marge.simpson.net>
Date:	Sat, 10 Aug 2013 07:55:28 +0200
From:	Mike Galbraith <bitbucket@...ine.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	x86@...nel.org, mingo@...nel.org, torvalds@...ux-foundation.org
Subject: Re: Re-tune x86 uaccess code for PREEMPT_VOLUNTARY

On Fri, 2013-08-09 at 21:42 -0700, H. Peter Anvin wrote: 
> On 08/09/2013 04:04 PM, Andi Kleen wrote:
> > 
> > This patch kit is an attempt to get us back to sane code, 
> > mostly by doing proper inlining and doing sleep checks in the right
> > place. Unfortunately I had to add one tree sweep to avoid an nasty
> > include loop.
> > 
> > It costs a bit of text space, but I think it's worth it
> > (if only to keep my blood pressure down while reading ftrace logs...)
> > 
> 
> Looks nice at first glance.
> 
> Now, here is a bigger question: shouldn't we be deprecating/getting rid
> of PREEMPT_VOUNTARY in favor of PREEMPT?

I sure hope not, PREEMPT munches throughput.  If you need PREEMPT, seems
to me what you _really_ need is PREEMPT_RT (the real deal), so
eventually depreciating PREEMPT makes more sense to me.

-Mike

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