From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id BC3F66B0062 for ; Wed, 3 Jun 2009 10:53:34 -0400 (EDT) Message-ID: <4A268DF8.6000701@redhat.com> Date: Wed, 03 Jun 2009 10:51:36 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [patch][v2] swap: virtual swap readahead References: <20090602223738.GA15475@cmpxchg.org> <20090602233457.GY1065@one.firstfloor.org> <20090603132751.GA1813@cmpxchg.org> In-Reply-To: <20090603132751.GA1813@cmpxchg.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Johannes Weiner Cc: Andi Kleen , Andrew Morton , Peter Zijlstra , Hugh Dickins , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: Johannes Weiner wrote: > On Wed, Jun 03, 2009 at 01:34:57AM +0200, Andi Kleen wrote: >> On Wed, Jun 03, 2009 at 12:37:39AM +0200, Johannes Weiner wrote: >>> + pgd = pgd_offset(vma->vm_mm, pos); >>> + if (!pgd_present(*pgd)) >>> + continue; >>> + pud = pud_offset(pgd, pos); >>> + if (!pud_present(*pud)) >>> + continue; >>> + pmd = pmd_offset(pud, pos); >>> + if (!pmd_present(*pmd)) >>> + continue; >>> + pte = pte_offset_map_lock(vma->vm_mm, pmd, pos, &ptl); >> You could be more efficient here by using the standard mm/* nested loop >> pattern that avoids relookup of everything in each iteration. I suppose >> it would mainly make a difference with 32bit highpte where mapping a pte >> can be somewhat costly. And you would take less locks this way. > > I ran into weird problems here. The above version is actually faster > in the benchmarks than writing a nested level walker or using > walk_page_range(). Still digging but it can take some time. Busy > week :( I'm not too worried about not walking the page tables, because swap is an extreme slow path anyway. -- All rights reversed. -- 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