From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752891Ab1IZXMi (ORCPT ); Mon, 26 Sep 2011 19:12:38 -0400 Received: from smtp-out.google.com ([74.125.121.67]:48517 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750884Ab1IZXMh (ORCPT ); Mon, 26 Sep 2011 19:12:37 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=date:from:to:cc:subject:message-id:in-reply-to:references: x-mailer:mime-version:content-type: content-transfer-encoding:x-system-of-record; b=GZ53TFWRI4y3GH1F4tUjeJQ36EwZAH4ZnjsIczLxk4PcV1yueBkFxU55r6Tp+zFe6 nQtZBkDVtpSPr26lLVKLA== Date: Mon, 26 Sep 2011 16:11:36 -0700 From: Andrew Morton To: Johannes Weiner Cc: Kautuk Consul , Mel Gorman , Minchan Kim , KAMEZAWA Hiroyuki , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Lee Schermerhorn , KOSAKI Motohiro , Andrew Morton Subject: Re: [patch] mm: remove sysctl to manually rescue unevictable pages Message-Id: <20110926161136.b4508ecb.akpm@google.com> In-Reply-To: <20110926112944.GC14333@redhat.com> References: <1316948380-1879-1-git-send-email-consul.kautuk@gmail.com> <20110926112944.GC14333@redhat.com> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 26 Sep 2011 13:29:45 +0200 Johannes Weiner wrote: > On Sun, Sep 25, 2011 at 04:29:40PM +0530, Kautuk Consul wrote: > > write_scan_unavictable_node checks the value req returned by > > strict_strtoul and returns 1 if req is 0. > > > > However, when strict_strtoul returns 0, it means successful conversion > > of buf to unsigned long. > > > > Due to this, the function was not proceeding to scan the zones for > > unevictable pages even though we write a valid value to the > > scan_unevictable_pages sys file. > > Given that there is not a real reason for this knob (anymore) and that > it apparently never really worked since the day it was introduced, how > about we just drop all that code instead? > Yes, let's remove it if at all possible. However, to be nice to people I do think we should emit a once-per-boot printk when someone tries to use it, then remove it for real at least a couple of kernel cycles later. Just in case someone's script or tuning app is trying to open that procfs file. > > --- > From: Johannes Weiner > Subject: mm: remove sysctl to manually rescue unevictable pages > > At one point, anonymous pages were supposed to go on the unevictable > list when no swap space was configured, and the idea was to manually > rescue those pages after adding swap and making them evictable again. > But nowadays, swap-backed pages on the anon LRU list are not scanned > without available swap space anyway, so there is no point in moving > them to a separate list anymore. > > The manual rescue could also be used in case pages were stranded on > the unevictable list due to race conditions. But the code has been > around for a while now and newly discovered bugs should be properly > reported and dealt with instead of relying on such a manual fixup. > > Signed-off-by: Johannes Weiner The changelog failed to note that the sysctl doesn't actually *work*. This is a pretty strong argument for removing it ;) Also, a reported-by:Kautuk would have been nice.