From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id 0C26E6B029B for ; Sun, 10 Sep 2017 21:13:38 -0400 (EDT) Received: by mail-pg0-f69.google.com with SMTP id t3so14011955pgt.7 for ; Sun, 10 Sep 2017 18:13:38 -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 201sor1596881pfu.68.2017.09.10.18.13.36 for (Google Transport Security); Sun, 10 Sep 2017 18:13:36 -0700 (PDT) Date: Sun, 10 Sep 2017 18:13:35 -0700 (PDT) From: David Rientjes Subject: Re: [patch 2/2] mm, compaction: persistently skip hugetlbfs pageblocks In-Reply-To: <74a33b7b-0586-c08a-cb2e-1c3d2872815d@suse.cz> Message-ID: References: <74a33b7b-0586-c08a-cb2e-1c3d2872815d@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, Joonsoo Kim On Fri, 1 Sep 2017, Vlastimil Babka wrote: > The pageblock_skip_persistent() function checks for HugeTLB pages of pageblock > order. When clearing pageblock skip bits for compaction, the bits are not > cleared for such pageblocks, because they cannot contain base pages suitable > for migration, nor free pages to use as migration targets. > > This optimization can be simply extended to all compound pages of order equal > or larger than pageblock order, because migrating such pages (if they support > it) cannot help sub-pageblock fragmentation. This includes THP's and also > gigantic HugeTLB pages, which the current implementation doesn't persistently > skip due to a strict pageblock_order equality check and not recognizing tail > pages. > > Additionally, this patch removes the pageblock_skip_persistent() calls from > migration and free scanner, since the generic compound page treatment together > with update_pageblock_skip() call will also lead to pageblocks starting with a > large enough compound page being immediately marked for skipping, which then > becomes persistent. > As mentioned in my other two emails, I'm not sure that persistently skipping thp memory is necessary and I disagree that we should not be persistently skipping pageblocks when cc->ignore_skip_hint is true. -- 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