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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CFDE1C77B76 for ; Fri, 21 Apr 2023 14:57:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233005AbjDUO5E (ORCPT ); Fri, 21 Apr 2023 10:57:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38480 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232215AbjDUO5C (ORCPT ); Fri, 21 Apr 2023 10:57:02 -0400 Received: from outbound-smtp18.blacknight.com (outbound-smtp18.blacknight.com [46.22.139.245]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3C764D324 for ; Fri, 21 Apr 2023 07:57:01 -0700 (PDT) Received: from mail.blacknight.com (pemlinmail05.blacknight.ie [81.17.254.26]) by outbound-smtp18.blacknight.com (Postfix) with ESMTPS id BDD041C3F9C for ; Fri, 21 Apr 2023 15:56:59 +0100 (IST) Received: (qmail 4981 invoked from network); 21 Apr 2023 14:56:59 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.21.103]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 21 Apr 2023 14:56:59 -0000 Date: Fri, 21 Apr 2023 15:56:57 +0100 From: Mel Gorman To: Johannes Weiner Cc: linux-mm@kvack.org, Kaiyang Zhao , Vlastimil Babka , David Rientjes , linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [RFC PATCH 25/26] mm: page_alloc: disallow fallbacks when 2M defrag is enabled Message-ID: <20230421145657.fnpjqkuyquy3z24t@techsingularity.net> References: <20230418191313.268131-1-hannes@cmpxchg.org> <20230418191313.268131-26-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20230418191313.268131-26-hannes@cmpxchg.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 18, 2023 at 03:13:12PM -0400, Johannes Weiner wrote: > Fallbacks are already unlikely due to watermarks being enforced > against MIGRATE_FREE blocks. Eliminate them altogether. This allows > compaction to look exclusively at movable blocks, reducing the number > of pageblocks it needs to scan on an ongoing basis. > > Signed-off-by: Johannes Weiner Conceptually this could be fun if a GFP_NOFS allocation cannot migrate enough memory to free one pageblock and there are no pageblocks available of the correct migratetype. Fallbacks might be unlikely but never being able to fallback is a livelock risk, no? -- Mel Gorman SUSE Labs