From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id B77679000BD for ; Mon, 26 Sep 2011 19:33:47 -0400 (EDT) Date: Mon, 26 Sep 2011 16:11:36 -0700 From: 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> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: 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 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. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org