From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f175.google.com (mail-wi0-f175.google.com [209.85.212.175]) by kanga.kvack.org (Postfix) with ESMTP id D4E6F6B0035 for ; Fri, 25 Jul 2014 12:27:34 -0400 (EDT) Received: by mail-wi0-f175.google.com with SMTP id ho1so1285820wib.14 for ; Fri, 25 Jul 2014 09:27:32 -0700 (PDT) Received: from service88.mimecast.com (service88.mimecast.com. [195.130.217.12]) by mx.google.com with ESMTP id pg3si18866411wjb.99.2014.07.25.09.27.30 for ; Fri, 25 Jul 2014 09:27:31 -0700 (PDT) From: Wilco Dijkstra Date: Fri, 25 Jul 2014 17:27:26 +0100 Subject: RE: Background page clearing Message-ID: References: <000001cfa81a$110d15c0$33274140$@com> <53D27590.2090500@intel.com> In-Reply-To: <53D27590.2090500@intel.com> Content-Language: en-US MIME-Version: 1.0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen , "linux-mm@kvack.org" > On 07/25/2014 08:06 AM, Wilco Dijkstra wrote: > > Is there a reason Linux does not do background page clearing like other= OSes to reduce this > > overhead? It would be a good fit for typical mobile workloads (bursts o= f high activity > followed by > > periods of low activity). > > If the page is being allocated, it is about to be used and be brought in > to the CPU's cache. If we zero it close to this use, we only pay to > bring it in to the CPU's cache once. Or so goes the theory... I can see the reasoning for 4KB pages and small allocations (eg. stack), but would that ever be true for huge pages? > I tried a zero-on-free implementation a year or so ago. It helped some > workloads and hurt others. The gains were not large enough or > widespread enough to merit pushing it in to the kernel. Was that literally zero-on-free or zero in the background? Was the result the same for different page sizes? My guess is that the result will be different for huge pages. Wilco -- IMPORTANT NOTICE: The contents of this email and any attachments are con= fidential and may also be privileged. If you are not the intended recipient= , please notify the sender immediately and do not disclose the contents to = any other person, use it for any purpose, or store or copy the information = in any medium. Thank you. ARM Limited, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ, Regist= ered in England & Wales, Company No: 2557590 ARM Holdings plc, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ, R= egistered in England & Wales, Company No: 2548782 -- 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