linux-kernel - Re: [PATCH 0/5] make *_gate_vma accept mm_struct instead of task

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Message-ID: <20110310170345.GE20504@alboin.amr.corp.intel.com>
Date:	Thu, 10 Mar 2011 09:03:45 -0800
From:	Andi Kleen <ak@...ux.intel.com>
To:	Stephen Wilson <wilsons@...rt.ca>
Cc:	x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux390@...ibm.com, Paul Mundt <lethal@...ux-sh.org>,
	Michel Lespinasse <walken@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	linux-sh@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] make *_gate_vma accept mm_struct instead of
 task_struct II

On Thu, Mar 10, 2011 at 11:54:14AM -0500, Stephen Wilson wrote:
> 
> On Thu, Mar 10, 2011 at 08:38:09AM -0800, Andi Kleen wrote:
> > On Thu, Mar 10, 2011 at 08:00:32AM -0800, Andi Kleen wrote:
> > > On Tue, Mar 08, 2011 at 07:31:56PM -0500, Stephen Wilson wrote:
> > > > The only architecture this change impacts in any significant way is x86_64.
> > > > The principle change on that architecture is to mirror TIF_IA32 via
> > > > a new flag in mm_context_t. 
> > > 
> > > The problem is -- you're adding a likely cache miss on mm_struct for
> > > every 32bit compat syscall now, even if they don't need mm_struct
> > > currently (and a lot of them do not) Unless there's a very good
> > > justification to make up for this performance issue elsewhere
> > > (including numbers) this seems like a bad idea.
> > 
> > Hmm I see you're only setting it on exec time actually on rereading
> > the patches. I thought you were changing TS_COMPAT which is in
> > the syscall path.
> > 
> > Never mind.  I have no problems with doing such a change on exec
> > time.
> 
> OK.  Great!  Does this mean I have your ACK'ed by or reviewed by?

I didn't read it all, but the first two patches looked ok.

-Andi
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