From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp01.in.ibm.com (e28smtp01.in.ibm.com [122.248.162.1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 4EB7414008A for ; Thu, 27 Mar 2014 17:20:17 +1100 (EST) Received: from /spool/local by e28smtp01.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 27 Mar 2014 11:50:12 +0530 Received: from d28relay01.in.ibm.com (d28relay01.in.ibm.com [9.184.220.58]) by d28dlp03.in.ibm.com (Postfix) with ESMTP id 4D6B61258059 for ; Thu, 27 Mar 2014 11:52:34 +0530 (IST) Received: from d28av03.in.ibm.com (d28av03.in.ibm.com [9.184.220.65]) by d28relay01.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s2R6JqWG60883076 for ; Thu, 27 Mar 2014 11:49:52 +0530 Received: from d28av03.in.ibm.com (localhost [127.0.0.1]) by d28av03.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s2R6K68Z026747 for ; Thu, 27 Mar 2014 11:50:07 +0530 Message-ID: <5333C315.3000405@linux.vnet.ibm.com> Date: Thu, 27 Mar 2014 11:50:05 +0530 From: Madhavan Srinivasan MIME-Version: 1.0 To: "Kirill A. Shutemov" Subject: Re: [PATCH 1/1] mm: move FAULT_AROUND_ORDER to arch/ References: <1395730215-11604-1-git-send-email-maddy@linux.vnet.ibm.com> <1395730215-11604-2-git-send-email-maddy@linux.vnet.ibm.com> <20140325173605.GA21411@node.dhcp.inet.fi> In-Reply-To: <20140325173605.GA21411@node.dhcp.inet.fi> Content-Type: text/plain; charset=ISO-8859-1 Cc: linux-arch@vger.kernel.org, riel@redhat.com, rusty@rustcorp.com.au, peterz@infradead.org, x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ak@linux.intel.com, paulus@samba.org, mgorman@suse.de, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, mingo@kernel.org, kirill.shutemov@linux.intel.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tuesday 25 March 2014 11:06 PM, Kirill A. Shutemov wrote: > On Tue, Mar 25, 2014 at 12:20:15PM +0530, Madhavan Srinivasan wrote: >> Kirill A. Shutemov with the commit 96bacfe542 introduced >> vm_ops->map_pages() for mapping easy accessible pages around >> fault address in hope to reduce number of minor page faults. >> Based on his workload runs, suggested FAULT_AROUND_ORDER >> (knob to control the numbers of pages to map) is 4. >> >> This patch moves the FAULT_AROUND_ORDER macro to arch/ for >> architecture maintainers to decide on suitable FAULT_AROUND_ORDER >> value based on performance data for that architecture. >> >> Signed-off-by: Madhavan Srinivasan >> --- >> arch/powerpc/include/asm/pgtable.h | 6 ++++++ >> arch/x86/include/asm/pgtable.h | 5 +++++ >> include/asm-generic/pgtable.h | 10 ++++++++++ >> mm/memory.c | 2 -- >> 4 files changed, 21 insertions(+), 2 deletions(-) >> >> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h >> index 3ebb188..9fcbd48 100644 >> --- a/arch/powerpc/include/asm/pgtable.h >> +++ b/arch/powerpc/include/asm/pgtable.h >> @@ -19,6 +19,12 @@ struct mm_struct; >> #endif >> >> /* >> + * With a few real world workloads that were run, >> + * the performance data showed that a value of 3 is more advantageous. >> + */ >> +#define FAULT_AROUND_ORDER 3 >> + >> +/* >> * We save the slot number & secondary bit in the second half of the >> * PTE page. We use the 8 bytes per each pte entry. >> */ >> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h >> index 938ef1d..8387a65 100644 >> --- a/arch/x86/include/asm/pgtable.h >> +++ b/arch/x86/include/asm/pgtable.h >> @@ -7,6 +7,11 @@ >> #include >> >> /* >> + * Based on Kirill's test results, fault around order is set to 4 >> + */ >> +#define FAULT_AROUND_ORDER 4 >> + >> +/* >> * Macro to mark a page protection value as UC- >> */ >> #define pgprot_noncached(prot) \ >> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h >> index 1ec08c1..62f7f07 100644 >> --- a/include/asm-generic/pgtable.h >> +++ b/include/asm-generic/pgtable.h >> @@ -7,6 +7,16 @@ >> #include >> #include >> >> + >> +/* >> + * Fault around order is a control knob to decide the fault around pages. >> + * Default value is set to 0UL (disabled), but the arch can override it as >> + * desired. >> + */ >> +#ifndef FAULT_AROUND_ORDER >> +#define FAULT_AROUND_ORDER 0UL >> +#endif > > FAULT_AROUND_ORDER == 0 case should be handled separately in > do_read_fault(): no reason to go to do_fault_around() if we are going to > fault in only one page. > ok agreed. I am thinking of adding FAULT_AROUND_ORDER check with map_pages check in the do_read_fault. Kindly share your thoughts. With regards Maddy