From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 8274F6B02F7 for ; Mon, 11 Sep 2017 17:13:39 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id x78so17194455pff.7 for ; Mon, 11 Sep 2017 14:13:39 -0700 (PDT) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id r59sor2772836plb.137.2017.09.11.14.13.37 for (Google Transport Security); Mon, 11 Sep 2017 14:13:38 -0700 (PDT) Date: Mon, 11 Sep 2017 14:13:36 -0700 (PDT) From: David Rientjes Subject: Re: [patch 1/2] mm, compaction: kcompactd should not ignore pageblock skip In-Reply-To: Message-ID: References: <5d578461-0982-f719-3a04-b2f3552dc7cc@suse.cz> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Andrew Morton , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Mon, 11 Sep 2017, Vlastimil Babka wrote: > > A follow-up change will set the pageblock skip for this memory since it is > > never useful for either scanner. > > """ > > > >> Also there's now a danger that in cases where there's no direct > >> compaction happening (just kcompactd), nothing will ever call > >> __reset_isolation_suitable(). > >> > > > > I'm not sure that is helpful in a context where no high-order memory can > > call direct compaction that kcompactd needlessly scanning the same memory > > over and over is beneficial. > > The point is that if it becomes beneficial again, we won't know as there > will be still be skip bits. > Why is kcompactd_do_work() not sometimes doing __reset_isolation_suitable() in the first place, if only to reset the per-zone migration and freeing scanner cached pfns? It seems fragile to rely on other threads doing direct compaction to reset the per-zone state of compaction. -- 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/ . Don't email: email@kvack.org