From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 893B6C04EBF for ; Wed, 5 Dec 2018 08:06:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 595D42084C for ; Wed, 5 Dec 2018 08:06:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 595D42084C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=techsingularity.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727247AbeLEIGx (ORCPT ); Wed, 5 Dec 2018 03:06:53 -0500 Received: from outbound-smtp26.blacknight.com ([81.17.249.194]:40668 "EHLO outbound-smtp26.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726102AbeLEIGv (ORCPT ); Wed, 5 Dec 2018 03:06:51 -0500 Received: from mail.blacknight.com (pemlinmail01.blacknight.ie [81.17.254.10]) by outbound-smtp26.blacknight.com (Postfix) with ESMTPS id 13FC5B86EA for ; Wed, 5 Dec 2018 08:06:49 +0000 (GMT) Received: (qmail 19886 invoked from network); 5 Dec 2018 08:06:49 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[37.228.245.71]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 5 Dec 2018 08:06:48 -0000 Date: Wed, 5 Dec 2018 08:06:47 +0000 From: Mel Gorman To: Andrew Morton Cc: Vlastimil Babka , David Rientjes , Andrea Arcangeli , Zi Yan , Michal Hocko , LKML , Linux-MM Subject: Re: [PATCH 5/5] mm: Stall movable allocations until kswapd progresses during serious external fragmentation event Message-ID: <20181205080647.GW23260@techsingularity.net> References: <20181123114528.28802-1-mgorman@techsingularity.net> <20181123114528.28802-6-mgorman@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 27, 2018 at 02:20:30PM +0100, Vlastimil Babka wrote: > > This patch has a marginal rate on fragmentation rates as it's rare for > > the stall logic to actually trigger but the small stalls can be enough for > > kswapd to catch up. How much that helps is variable but probably worthwhile > > for long-term allocation success rates. It is possible to eliminate > > fragmentation events entirely with tuning due to this patch although that > > would require careful evaluation to determine if it's worthwhile. > > > > Signed-off-by: Mel Gorman > > The gains here are relatively smaller and noisier than for the previous > patches. Also I'm afraid that once antifrag loses against the ultimate > adversary workload (see the "Caching/buffers become useless after some > time" thread), then this might result in adding stalls to a workload > that has no other options but to allocate movable pages from partially > filled unmovable blocks, because that's simply the majority of > pageblocks in the system, and the stalls can't help the situation. If > that proves to be true, we could revert, but then there's the new > user-visible tunable... and that all makes it harder for me to decide > about this patch :) If only we could find out early while this is in > linux-mm/linux-next... > Andrew, would you mind dropping this patch from mmotm please? I think the benefit is marginal relative to the potential loss. If it turns out we ever really do need it then hopefully there will be better data supporting it. Thanks. -- Mel Gorman SUSE Labs