From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755326AbaEOR3h (ORCPT ); Thu, 15 May 2014 13:29:37 -0400 Received: from mail-pb0-f50.google.com ([209.85.160.50]:55987 "EHLO mail-pb0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752591AbaEOR3f (ORCPT ); Thu, 15 May 2014 13:29:35 -0400 Date: Thu, 15 May 2014 10:28:17 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Madhavan Srinivasan 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, dave.hansen@intel.com Subject: Re: [PATCH V4 0/2] mm: FAULT_AROUND_ORDER patchset performance data for powerpc In-Reply-To: <537479E7.90806@linux.vnet.ibm.com> Message-ID: References: <1399541296-18810-1-git-send-email-maddy@linux.vnet.ibm.com> <537479E7.90806@linux.vnet.ibm.com> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 15 May 2014, Madhavan Srinivasan wrote: > > Hi Ingo, > > Do you have any comments for the latest version of the patchset. If > not, kindly can you pick it up as is. > > > With regards > Maddy > > > Kirill A. Shutemov with 8c6e50b029 commit introduced > > vm_ops->map_pages() for mapping easy accessible pages around > > fault address in hope to reduce number of minor page faults. > > > > This patch creates infrastructure to modify the FAULT_AROUND_ORDER > > value using mm/Kconfig. This will enable architecture maintainers > > to decide on suitable FAULT_AROUND_ORDER value based on > > performance data for that architecture. First patch also defaults > > FAULT_AROUND_ORDER Kconfig element to 4. Second patch list > > out the performance numbers for powerpc (platform pseries) and > > initialize the fault around order variable for pseries platform of > > powerpc. Sorry for not commenting earlier - just reminded by this ping to Ingo. I didn't study your numbers, but nowhere did I see what PAGE_SIZE you use. arch/powerpc/Kconfig suggests that Power supports base page size of 4k, 16k, 64k or 256k. I would expect your optimal fault_around_order to depend very much on the base page size. Perhaps fault_around_size would provide a more useful default? Hugh