Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756213AbZG2ABD (ORCPT ); Tue, 28 Jul 2009 20:01:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756120AbZG2ABA (ORCPT ); Tue, 28 Jul 2009 20:01:00 -0400 Received: from mail-bw0-f221.google.com ([209.85.218.221]:39983 "EHLO mail-bw0-f221.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753260AbZG2AA5 convert rfc822-to-8bit (ORCPT ); Tue, 28 Jul 2009 20:00:57 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=pN2EX4hZl5RAaPVM1PxGw7FhKJELYuShyrj3O/mXlmt5lEpjmT7CVL1JwWym8qWYBu KaX3L2HFCIjSw9WaIOADNlOBhFgoF0zhq6omgQRgtob9R4O4VLmIdogOx2+ypPyEa5AO a4pXzuK7a8vDk0OxoGOllRW2ocX5RJMkosBOc= MIME-Version: 1.0 In-Reply-To: <20090728165245.65d5cb23.akpm@linux-foundation.org> References: <4A693122.6060503@gmail.com> <7928e7bd0907271514y699d1de4j54f9c562b94ef0cc@mail.gmail.com> <7928e7bd0907271638x5ddbfd2ckba2802338a33765a@mail.gmail.com> <4A6F2AF4.6050505@gmail.com> <4A6F8115.7000500@gmail.com> <20090728165245.65d5cb23.akpm@linux-foundation.org> Date: Tue, 28 Jul 2009 17:00:54 -0700 Message-ID: <7928e7bd0907281700s13d9937yc3b2933b13cfae9f@mail.gmail.com> Subject: Re: [PATCH 1/1] pagemap clear_refs: modify to specify anon or mapped vma clearing From: Moussa Ba To: Andrew Morton Cc: linux-kernel@vger.kernel.org, rientjes@google.com, xiyou.wangcong@gmail.com, adobriyan@gmail.com, mpm@selenic.com, mel@csn.ul.ie, yinghan@google.com, npiggin@suse.de, jaredeh@gmail.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1460 Lines: 32 The patch makes the clear_refs more versatile in adding the option to select anonymous pages or file backed pages for clearing. This addition has a measurable impact on user space application performance as it decreases the number of pagewalks in scenarios where one is only interested in a specific type of page (anonymous or file mapped). On Tue, Jul 28, 2009 at 4:52 PM, Andrew Morton wrote: > On Tue, 28 Jul 2009 15:52:05 -0700 > "Moussa A. Ba" wrote: > >> This patch adds anonymous and file backed filters to the clear_refs interface. >> echo 1 > /proc/PID/clear_refs resets the bits on all pages >> echo 2 > /proc/PID/clear_refs resets the bits on anonymous pages only >> echo 3 > /proc/PID/clear_refs resets the bits on file backed pages only >> Any other value is ignored > > The changelog is missing any rationale for making this change. > Originally we were told that it "makes the clear_refs proc interface a > bit more versatile", but that's a bit thin. > > How do we justify making this change to Linux? ?What value does it > have? ?Can you describe a usage scenario which would help people > understand the usefulness of the change? > > Thanks. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/