From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f49.google.com (mail-pa0-f49.google.com [209.85.220.49]) by kanga.kvack.org (Postfix) with ESMTP id E84156B0069 for ; Sat, 18 Oct 2014 16:36:29 -0400 (EDT) Received: by mail-pa0-f49.google.com with SMTP id hz1so2746151pad.22 for ; Sat, 18 Oct 2014 13:36:29 -0700 (PDT) Received: from mga02.intel.com (mga02.intel.com. [134.134.136.20]) by mx.google.com with ESMTP id kp1si4168197pbd.33.2014.10.18.13.36.28 for ; Sat, 18 Oct 2014 13:36:28 -0700 (PDT) Date: Sat, 18 Oct 2014 13:22:07 -0400 From: Matthew Wilcox Subject: Re: [PATCH v11 04/21] mm: Allow page fault handlers to perform the COW Message-ID: <20141018172207.GN11522@wil.cx> References: <1411677218-29146-1-git-send-email-matthew.r.wilcox@intel.com> <1411677218-29146-5-git-send-email-matthew.r.wilcox@intel.com> <20141016091136.GC19075@thinkos.etherlink> <20141016194815.GD11522@wil.cx> <289646725.10903.1413560101974.JavaMail.zimbra@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <289646725.10903.1413560101974.JavaMail.zimbra@efficios.com> Sender: owner-linux-mm@kvack.org List-ID: To: Mathieu Desnoyers Cc: Matthew Wilcox , Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Fri, Oct 17, 2014 at 03:35:01PM +0000, Mathieu Desnoyers wrote: > > > The page fault handler being very much performance sensitive, I'm > > > wondering if it would not be better to move cow_page near the end of > > > struct vm_fault, so that the "page" field can stay on the first > > > cache line. > > Although it's pretty much always true that recent architectures L2 cache > lines are 64 bytes, I was more thinking about L1 cache lines, which are, > at least on moderately old Intel Pentium HW, 32 bytes in size (AFAIK > Pentium II and III). > > It remains to be seen whether we care about performance that much on this > kind of HW though. Oh, I just remembered ... this data structure is on the stack, so if it's not cache-hot, something has gone horribly wrong. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org