From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id 76AD76B0253 for ; Wed, 22 Jun 2016 17:56:19 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id 143so132750036pfx.0 for ; Wed, 22 Jun 2016 14:56:19 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id em6si2174727pac.71.2016.06.22.14.56.18 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 Jun 2016 14:56:18 -0700 (PDT) Date: Wed, 22 Jun 2016 14:56:17 -0700 From: Andrew Morton Subject: Re: [patch] mm, compaction: abort free scanner if split fails Message-Id: <20160622145617.79197acff1a7e617b9d9d393@linux-foundation.org> In-Reply-To: References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Vlastimil Babka , Minchan Kim , Joonsoo Kim , Mel Gorman , Hugh Dickins , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org On Tue, 21 Jun 2016 18:22:49 -0700 (PDT) David Rientjes wrote: > If the memory compaction free scanner cannot successfully split a free > page (only possible due to per-zone low watermark), terminate the free > scanner rather than continuing to scan memory needlessly. If the > watermark is insufficient for a free page of order <= cc->order, then > terminate the scanner since all future splits will also likely fail. > > This prevents the compaction freeing scanner from scanning all memory on > very large zones (very noticeable for zones > 128GB, for instance) when > all splits will likely fail while holding zone->lock. > This collides pretty heavily with Joonsoo's "mm/compaction: split freepages without holding the zone lock". I ended up with this, in isolate_freepages_block(): /* Found a free page, will break it into order-0 pages */ order = page_order(page); isolated = __isolate_free_page(page, page_order(page)); set_page_private(page, order); total_isolated += isolated; cc->nr_freepages += isolated; list_add_tail(&page->lru, freelist); if (!strict && cc->nr_migratepages <= cc->nr_freepages) { blockpfn += isolated; break; } /* Advance to the end of split page */ blockpfn += isolated - 1; cursor += isolated - 1; continue; isolate_fail: -- 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