Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757588AbcK3OQ0 (ORCPT ); Wed, 30 Nov 2016 09:16:26 -0500 Received: from outbound-smtp06.blacknight.com ([81.17.249.39]:55250 "EHLO outbound-smtp06.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756261AbcK3OQS (ORCPT ); Wed, 30 Nov 2016 09:16:18 -0500 Date: Wed, 30 Nov 2016 14:16:13 +0000 From: Mel Gorman To: Michal Hocko Cc: Andrew Morton , Christoph Lameter , Vlastimil Babka , Johannes Weiner , Linux-MM , Linux-Kernel Subject: Re: [PATCH] mm: page_alloc: High-order per-cpu page allocator v3 Message-ID: <20161130141613.gnf63khbrzrps7ip@techsingularity.net> References: <20161127131954.10026-1-mgorman@techsingularity.net> <20161130130549.GE18432@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20161130130549.GE18432@dhcp22.suse.cz> User-Agent: Mutt/1.6.2 (2016-07-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2811 Lines: 89 On Wed, Nov 30, 2016 at 02:05:50PM +0100, Michal Hocko wrote: > On Sun 27-11-16 13:19:54, Mel Gorman wrote: > [...] > > @@ -2588,18 +2594,22 @@ struct page *buffered_rmqueue(struct zone *preferred_zone, > > struct page *page; > > bool cold = ((gfp_flags & __GFP_COLD) != 0); > > > > - if (likely(order == 0)) { > > + if (likely(order <= PAGE_ALLOC_COSTLY_ORDER)) { > > struct per_cpu_pages *pcp; > > struct list_head *list; > > > > local_irq_save(flags); > > do { > > + unsigned int pindex; > > + > > + pindex = order_to_pindex(migratetype, order); > > pcp = &this_cpu_ptr(zone->pageset)->pcp; > > - list = &pcp->lists[migratetype]; > > + list = &pcp->lists[pindex]; > > if (list_empty(list)) { > > - pcp->count += rmqueue_bulk(zone, 0, > > + int nr_pages = rmqueue_bulk(zone, order, > > pcp->batch, list, > > migratetype, cold); > > + pcp->count += (nr_pages << order); > > if (unlikely(list_empty(list))) > > goto failed; > > just a nit, we can reorder the check and the count update because nobody > could have stolen pages allocated by rmqueue_bulk. Ok, it's minor but I can do that. > I would also consider > nr_pages a bit misleading because we get a number or allocated elements. > Nothing to lose sleep over... > I didn't think of a clearer name because in this sort of context, I consider a high-order page to be a single page. > > } > > But... Unless I am missing something this effectively means that we do > not exercise high order atomic reserves. Shouldn't we fallback to > the locked __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC) for > order > 0 && ALLOC_HARDER ? Or is this just hidden in some other code > path which I am not seeing? > Good spot, would this be acceptable to you? diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 91dc68c2a717..94808f565f74 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2609,9 +2609,18 @@ struct page *buffered_rmqueue(struct zone *preferred_zone, int nr_pages = rmqueue_bulk(zone, order, pcp->batch, list, migratetype, cold); - pcp->count += (nr_pages << order); - if (unlikely(list_empty(list))) + if (unlikely(list_empty(list))) { + /* + * Retry high-order atomic allocs + * from the buddy list which may + * use MIGRATE_HIGHATOMIC. + */ + if (order && (alloc_flags & ALLOC_HARDER)) + goto try_buddylist; + goto failed; + } + pcp->count += (nr_pages << order); } if (cold) @@ -2624,6 +2633,7 @@ struct page *buffered_rmqueue(struct zone *preferred_zone, } while (check_new_pcp(page)); } else { +try_buddylist: /* * We most definitely don't want callers attempting to * allocate greater than order-1 page units with __GFP_NOFAIL. -- Mel Gorman SUSE Labs