From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id BFC3C6B0253 for ; Tue, 17 May 2016 21:22:56 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id 4so66756489pfw.0 for ; Tue, 17 May 2016 18:22:56 -0700 (PDT) Received: from lgeamrelo12.lge.com (LGEAMRELO12.lge.com. [156.147.23.52]) by mx.google.com with ESMTP id 2si8190316pai.214.2016.05.17.18.22.54 for ; Tue, 17 May 2016 18:22:55 -0700 (PDT) Date: Wed, 18 May 2016 10:22:59 +0900 From: Minchan Kim Subject: Re: [PATCH] mm: make faultaround produce old ptes Message-ID: <20160518012259.GA21490@bbox> References: <1463488366-47723-1-git-send-email-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 In-Reply-To: <1463488366-47723-1-git-send-email-kirill.shutemov@linux.intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Andrew Morton , linux-mm@kvack.org, Mel Gorman , Rik van Riel , Michal Hocko , Vinayak Menon On Tue, May 17, 2016 at 03:32:46PM +0300, Kirill A. Shutemov wrote: > Currently, faultaround code produces young pte. This can screw up vmscan > behaviour[1], as it makes vmscan think that these pages are hot and not > push them out on first round. > > Let modify faultaround to produce old pte, so they can easily be > reclaimed under memory pressure. > > This can to some extend defeat purpose of faultaround on machines > without hardware accessed bit as it will not help up with reducing > number of minor page faults. > > We may want to disable faultaround on such machines altogether, but > that's subject for separate patchset. > > [1] https://lkml.kernel.org/r/1460992636-711-1-git-send-email-vinmenon@codeaurora.org > > Signed-off-by: Kirill A. Shutemov > Cc: Mel Gorman > Cc: Rik van Riel > Cc: Michal Hocko > Cc: Vinayak Menon > Cc: Minchan Kim I tested 512M mmap sequential word read test on non-HW access bit system (i.e., ARM) and confirmed it doesn't increase minor fault any more. = old = minor fault: 131291 elapsed time: 6747645 usec = new = minor fault: 131291 elapsed time: 6709263 usec 0.56% benefit Acked-by: Minchan Kim -- 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