linux-kernel - Re: [patch 2/2] [PATCH] mm: Save soft-dirty bits on file pages

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Date:	Tue, 13 Aug 2013 19:37:03 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, xemul@...allels.com, mpm@...enic.com,
	xiaoguangrong@...ux.vnet.ibm.com, mtosatti@...hat.com,
	kosaki.motohiro@...il.com, sfr@...b.auug.org.au,
	peterz@...radead.org, aneesh.kumar@...ux.vnet.ibm.com,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 2/2] [PATCH] mm: Save soft-dirty bits on file pages

On Tue, Aug 13, 2013 at 08:14:39AM -0700, H. Peter Anvin wrote:
> On 08/12/2013 10:02 PM, Cyrill Gorcunov wrote:
> > 
> > There is a case when you don't need a mask completely. And because this
> > pte conversion is on hot path and time critical I kept generated code
> > as it was (even if that lead to slightly less clear source code).
> > 
> 
> Does it actually matter, generated-code-wise, or is the compiler smart
> enough to figure it out?  The reason I'm asking is because it makes the

gcc-4.7.2 is smart enough to suppress useless masking (ie ((1u << 31) - 1))
completely but I don't know if this can be assumed for all gcc series.

> code much harder to follow.

I see. OK, I'll try to prepare more readable macro helpers.

> 
> The other thing is can we please pretty please call it something other
> than "frob"?

Sure.
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