From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx173.postini.com [74.125.245.173]) by kanga.kvack.org (Postfix) with SMTP id 8806F6B0062 for ; Mon, 12 Aug 2013 18:37:27 -0400 (EDT) Date: Mon, 12 Aug 2013 15:37:25 -0700 From: Andrew Morton Subject: Re: [patch 2/2] [PATCH] mm: Save soft-dirty bits on file pages Message-Id: <20130812153725.6ac5135a86994e4d766723f9@linux-foundation.org> In-Reply-To: References: <20130730204154.407090410@gmail.com> <20130730204654.966378702@gmail.com> <20130807132812.60ad4bfe85127794094d385e@linux-foundation.org> <20130808145120.GA1775@moon> <20130812145720.3b722b066fe1bd77291331e5@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andy Lutomirski Cc: Cyrill Gorcunov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, xemul@parallels.com, mpm@selenic.com, xiaoguangrong@linux.vnet.ibm.com, mtosatti@redhat.com, kosaki.motohiro@gmail.com, sfr@canb.auug.org.au, peterz@infradead.org, aneesh.kumar@linux.vnet.ibm.com, Ingo Molnar , "H. Peter Anvin" , Thomas Gleixner On Mon, 12 Aug 2013 15:28:06 -0700 Andy Lutomirski wrote: > > +#define _mfrob(v,r,m,l) ((((v) >> (r)) & (m)) << (l)) > > +#define __frob(v,r,l) (((v) >> (r)) << (l)) > > + > > #ifdef CONFIG_MEM_SOFT_DIRTY > > > > If I'm understanding this right, the idea is to take the bits in the > range a..b of v and stick them at c..d, where a-b == c-d. Would it > make sense to change this to look something like > > #define __frob(v, inmsb, inlsb, outlsb) ((v >> inlsb) & ((1<<(inmsb - > inlsb + 1)-1) << outlsb) > > For extra fun, there could be an __unfrob macro that takes the same > inmsg, inlsb, outlsb parameters but undoes it so that it's (more) > clear that the operations that are supposed to be inverses are indeed > inverses. hm, I seem to remember writing drivers/net/ethernet/3com/3c59x.c:BFINS() and BFEXT() shortly after the invention of the electronic computer. I'm kinda surprised that we don't already have something like this in kernel.h or somewhere - there's surely a ton of code which does such things. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org