From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932379AbcFUAwv (ORCPT ); Mon, 20 Jun 2016 20:52:51 -0400 Received: from mail-pf0-f181.google.com ([209.85.192.181]:36724 "EHLO mail-pf0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752445AbcFUAwq (ORCPT ); Mon, 20 Jun 2016 20:52:46 -0400 Date: Mon, 20 Jun 2016 17:52:43 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Ganesh Mahendran cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, vbabka@suse.cz, iamjoonsoo.kim@lge.com, mhocko@suse.com, mina86@mina86.com, minchan@kernel.org, mgorman@techsingularity.net, kirill.shutemov@linux.intel.com, izumi.taku@jp.fujitsu.com, hannes@cmpxchg.org, khandual@linux.vnet.ibm.com, bsingharora@gmail.com Subject: Re: [PATCH v3] mm/compaction: remove unnecessary order check in direct compact path In-Reply-To: <1466044956-3690-1-git-send-email-opensource.ganesh@gmail.com> Message-ID: References: <1466044956-3690-1-git-send-email-opensource.ganesh@gmail.com> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 16 Jun 2016, Ganesh Mahendran wrote: > diff --git a/mm/compaction.c b/mm/compaction.c > index fbb7b38..dcfaf57 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1686,12 +1686,16 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order, > > *contended = COMPACT_CONTENDED_NONE; > > - /* Check if the GFP flags allow compaction */ > + /* > + * Check if this is an order-0 request and > + * if the GFP flags allow compaction. > + */ This seems obvious. > if (!order || !may_enter_fs || !may_perform_io) > return COMPACT_SKIPPED; > > trace_mm_compaction_try_to_compact_pages(order, gfp_mask, mode); > > + current->flags |= PF_MEMALLOC; > /* Compact each zone in the list */ > for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx, > ac->nodemask) { > @@ -1768,6 +1772,7 @@ break_loop: > all_zones_contended = 0; > break; > } > + current->flags &= ~PF_MEMALLOC; > > /* > * If at least one zone wasn't deferred or skipped, we report if all Compaction don't touch task_struct flags and PF_MEMALLOC is flag used primarily by the page allocator, moving this to try_to_compact_pages() doesn't make sense. You could remove the !order check in try_to_compact_pages(), but I don't think it offers anything substantial.