From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753638AbaC0GUT (ORCPT ); Thu, 27 Mar 2014 02:20:19 -0400 Received: from e28smtp05.in.ibm.com ([122.248.162.5]:59337 "EHLO e28smtp05.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750777AbaC0GUQ (ORCPT ); Thu, 27 Mar 2014 02:20:16 -0400 Message-ID: <5333C315.3000405@linux.vnet.ibm.com> Date: Thu, 27 Mar 2014 11:50:05 +0530 From: Madhavan Srinivasan User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: "Kirill A. Shutemov" CC: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, x86@kernel.org, benh@kernel.crashing.org, paulus@samba.org, kirill.shutemov@linux.intel.com, rusty@rustcorp.com.au, akpm@linux-foundation.org, riel@redhat.com, mgorman@suse.de, ak@linux.intel.com, peterz@infradead.org, mingo@kernel.org 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 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14032706-8256-0000-0000-00000C26530F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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