Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754958Ab0AGGdH (ORCPT ); Thu, 7 Jan 2010 01:33:07 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752496Ab0AGGdF (ORCPT ); Thu, 7 Jan 2010 01:33:05 -0500 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:48398 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751444Ab0AGGdC (ORCPT ); Thu, 7 Jan 2010 01:33:02 -0500 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Hugh Dickins , Ralf Baechle , linux-mips@linux-mips.org, Carsten Otte Subject: [PATCH] mips,mm: Reinstate move_pte optimization Cc: kosaki.motohiro@jp.fujitsu.com, Peter Zijlstra , KAMEZAWA Hiroyuki , Nick Piggin , Ingo Molnar , LKML , Thomas Gleixner , Darren Hart , Ulrich Drepper In-Reply-To: References: <20091225083305.AA78.A69D9226@jp.fujitsu.com> Message-Id: <20100107151527.8784.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Thu, 7 Jan 2010 15:32:57 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3143 Lines: 89 CC to mips folks. > If something like this or your replacment does go forward, > then I think that test is better inside the "if (!page->mapping)" > below. Admittedly that adds even more mm-dependence here (relying > on a zero page to have NULL page->mapping); but isn't page_to_pfn() > one of those functions which is trivial on many configs but expensive > on some? Better call it only in the rare case that it's needed. > > Though wouldn't it be even better not to use is_zero_pfn() at all? > That was convenient in mm/memory.c because it had the pfn or pte right > at hand, but here a traditional (page == ZERO_PAGE(address)) would be > more efficient. > > Which would save having to move is_zero_pfn() from mm/memory.c > to include/linux/mm.h - I'd prefer to keep it private if we can. > But for completeness, this would involve resurrecting the 2.6.19 > MIPS move_pte(), which makes sure mremap() move doesn't interfere > with our assumptions. Something like > > #define __HAVE_ARCH_MOVE_PTE > pte_t move_pte(pte_t pte, pgprot_t prot, unsigned long old_addr, > unsigned long new_addr) > { > if (pte_present(pte) && is_zero_pfn(pte_pfn(pte))) > pte = mk_pte(ZERO_PAGE(new_addr), prot); > return pte; > } > > in arch/mips/include/asm/pgtable.h. I agree with resurrecting mips move_pte. At least your patch passed my cross compile test :) Ralf, can you please review following patch? ====================================================== Subject: [PATCH] mips,mm: Reinstate move_pte optimization From: Hugh Dickins About three years ago, we removed mips specific move_pte by commit 701dfbc1cb (mm: mremap correct rmap accounting). because it is only small optimization and it has bug. However new zero-page thing doesn't have such problem and behavior consistency of mremap have worth a bit. This patch reinstate it. Signed-off-by: Hugh Dickins Signed-off-by: KOSAKI Motohiro Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: Nick Piggin Cc: Carsten Otte --- arch/mips/include/asm/pgtable.h | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h index 1854336..6ad2f73 100644 --- a/arch/mips/include/asm/pgtable.h +++ b/arch/mips/include/asm/pgtable.h @@ -387,6 +387,14 @@ static inline int io_remap_pfn_range(struct vm_area_struct *vma, remap_pfn_range(vma, vaddr, pfn, size, prot) #endif +#define __HAVE_ARCH_MOVE_PTE +pte_t move_pte(pte_t pte, pgprot_t prot, unsigned long old_addr, unsigned long new_addr) +{ + if (pte_present(pte) && is_zero_pfn(pte_pfn(pte))) + pte = mk_pte(ZERO_PAGE(new_addr), prot); + return pte; +} + #include /* -- 1.6.5.2 -- 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/