Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932225Ab3HMV3D (ORCPT ); Tue, 13 Aug 2013 17:29:03 -0400 Received: from mail-lb0-f173.google.com ([209.85.217.173]:44743 "EHLO mail-lb0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932070Ab3HMV3B (ORCPT ); Tue, 13 Aug 2013 17:29:01 -0400 Date: Wed, 14 Aug 2013 01:28:57 +0400 From: Cyrill Gorcunov To: "H. Peter Anvin" Cc: Andy Lutomirski , Andrew Morton , 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 , Thomas Gleixner Subject: Re: [patch 2/2] [PATCH] mm: Save soft-dirty bits on file pages Message-ID: <20130813212857.GI2869@moon> References: <20130730204154.407090410@gmail.com> <20130730204654.966378702@gmail.com> <20130807132812.60ad4bfe85127794094d385e@linux-foundation.org> <20130808145120.GA1775@moon> <20130812145720.3b722b066fe1bd77291331e5@linux-foundation.org> <20130813050213.GA2869@moon> <520A4D5F.6020401@zytor.com> <20130813153703.GE2869@moon> <520A622B.7020900@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <520A622B.7020900@zytor.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4817 Lines: 111 On Tue, Aug 13, 2013 at 09:43:23AM -0700, H. Peter Anvin wrote: > On 08/13/2013 08:37 AM, Cyrill Gorcunov wrote: > >> > >> 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. > > > > I would be highly surprised if it wasn't the case for any gcc we care about. Does below one looks better? (Btw, what about the snippet we have there as well #if _PAGE_BIT_FILE < _PAGE_BIT_PROTNONE #define PTE_FILE_SHIFT2 (_PAGE_BIT_FILE + 1) #define PTE_FILE_SHIFT3 (_PAGE_BIT_PROTNONE + 1) #else #define PTE_FILE_SHIFT2 (_PAGE_BIT_PROTNONE + 1) #define PTE_FILE_SHIFT3 (_PAGE_BIT_FILE + 1) #endif where #define _PAGE_BIT_PROTNONE _PAGE_BIT_GLOBAL -> 8 #define _PAGE_BIT_FILE _PAGE_BIT_DIRTY -> 6 so I wonder where the cases on x86 when _PAGE_BIT_FILE > _PAGE_BIT_PROTNONE, what i'm missing here?) --- arch/x86/include/asm/pgtable-2level.h | 37 +++++++++++++++++++--------------- 1 file changed, 21 insertions(+), 16 deletions(-) Index: linux-2.6.git/arch/x86/include/asm/pgtable-2level.h =================================================================== --- linux-2.6.git.orig/arch/x86/include/asm/pgtable-2level.h +++ linux-2.6.git/arch/x86/include/asm/pgtable-2level.h @@ -55,8 +55,11 @@ static inline pmd_t native_pmdp_get_and_ #define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp) #endif -#define _mfrob(v,r,m,l) ((((v) >> (r)) & (m)) << (l)) -#define __frob(v,r,l) (((v) >> (r)) << (l)) +/* + * For readable bitfield manipulations. + */ +#define PTE_FILE_NOMASK (-1U) +#define __bfop(v,r,m,l) ((((v) >> (r)) & (m)) << (l)) #ifdef CONFIG_MEM_SOFT_DIRTY @@ -83,17 +86,17 @@ static inline pmd_t native_pmdp_get_and_ #define PTE_FILE_LSHIFT4 (PTE_FILE_BITS1 + PTE_FILE_BITS2 + PTE_FILE_BITS3) #define pte_to_pgoff(pte) \ - (_mfrob((pte).pte_low, PTE_FILE_SHIFT1, PTE_FILE_MASK1, 0) + \ - _mfrob((pte).pte_low, PTE_FILE_SHIFT2, PTE_FILE_MASK2, PTE_FILE_LSHIFT2) + \ - _mfrob((pte).pte_low, PTE_FILE_SHIFT3, PTE_FILE_MASK3, PTE_FILE_LSHIFT3) + \ - __frob((pte).pte_low, PTE_FILE_SHIFT4, PTE_FILE_LSHIFT4)) + (__bfop((pte).pte_low, PTE_FILE_SHIFT1, PTE_FILE_MASK1, 0) + \ + __bfop((pte).pte_low, PTE_FILE_SHIFT2, PTE_FILE_MASK2, PTE_FILE_LSHIFT2) + \ + __bfop((pte).pte_low, PTE_FILE_SHIFT3, PTE_FILE_MASK3, PTE_FILE_LSHIFT3) + \ + __bfop((pte).pte_low, PTE_FILE_SHIFT4, PTE_FILE_NOMASK, PTE_FILE_LSHIFT4)) #define pgoff_to_pte(off) \ ((pte_t) { .pte_low = \ - _mfrob(off, 0, PTE_FILE_MASK1, PTE_FILE_SHIFT1) + \ - _mfrob(off, PTE_FILE_LSHIFT2, PTE_FILE_MASK2, PTE_FILE_SHIFT2) + \ - _mfrob(off, PTE_FILE_LSHIFT3, PTE_FILE_MASK3, PTE_FILE_SHIFT3) + \ - __frob(off, PTE_FILE_LSHIFT4, PTE_FILE_SHIFT4) + \ + __bfop(off, 0, PTE_FILE_MASK1, PTE_FILE_SHIFT1) + \ + __bfop(off, PTE_FILE_LSHIFT2, PTE_FILE_MASK2, PTE_FILE_SHIFT2) + \ + __bfop(off, PTE_FILE_LSHIFT3, PTE_FILE_MASK3, PTE_FILE_SHIFT3) + \ + __bfop(off, PTE_FILE_LSHIFT4, PTE_FILE_NOMASK, PTE_FILE_SHIFT4) + \ _PAGE_FILE }) #else /* CONFIG_MEM_SOFT_DIRTY */ @@ -121,19 +124,21 @@ static inline pmd_t native_pmdp_get_and_ #define PTE_FILE_LSHIFT3 (PTE_FILE_BITS1 + PTE_FILE_BITS2) #define pte_to_pgoff(pte) \ - (_mfrob((pte).pte_low, PTE_FILE_SHIFT1, PTE_FILE_MASK1, 0) + \ - _mfrob((pte).pte_low, PTE_FILE_SHIFT2, PTE_FILE_MASK2, PTE_FILE_LSHIFT2) + \ - __frob((pte).pte_low, PTE_FILE_SHIFT3, PTE_FILE_LSHIFT3)) + (__bfop((pte).pte_low, PTE_FILE_SHIFT1, PTE_FILE_MASK1, 0) + \ + __bfop((pte).pte_low, PTE_FILE_SHIFT2, PTE_FILE_MASK2, PTE_FILE_LSHIFT2) + \ + __bfop((pte).pte_low, PTE_FILE_SHIFT3, PTE_FILE_NOMASK, PTE_FILE_LSHIFT3)) #define pgoff_to_pte(off) \ ((pte_t) { .pte_low = \ - _mfrob(off, 0, PTE_FILE_MASK1, PTE_FILE_SHIFT1) + \ - _mfrob(off, PTE_FILE_LSHIFT2, PTE_FILE_MASK2, PTE_FILE_SHIFT2) + \ - __frob(off, PTE_FILE_LSHIFT3, PTE_FILE_SHIFT3) + \ + __bfop(off, 0, PTE_FILE_MASK1, PTE_FILE_SHIFT1) + \ + __bfop(off, PTE_FILE_LSHIFT2, PTE_FILE_MASK2, PTE_FILE_SHIFT2) + \ + __bfop(off, PTE_FILE_LSHIFT3, PTE_FILE_NOMASK, PTE_FILE_SHIFT3) + \ _PAGE_FILE }) #endif /* CONFIG_MEM_SOFT_DIRTY */ +#undef __bfop + /* Encode and de-code a swap entry */ #if _PAGE_BIT_FILE < _PAGE_BIT_PROTNONE #define SWP_TYPE_BITS (_PAGE_BIT_FILE - _PAGE_BIT_PRESENT - 1) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/