Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752909Ab2KIMQK (ORCPT ); Fri, 9 Nov 2012 07:16:10 -0500 Received: from gir.skynet.ie ([193.1.99.77]:57601 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751228Ab2KIMQF (ORCPT ); Fri, 9 Nov 2012 07:16:05 -0500 Date: Fri, 9 Nov 2012 12:16:02 +0000 From: Mel Gorman To: Rafael Aquini Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Rusty Russell , "Michael S. Tsirkin" , Rik van Riel , Andi Kleen , Andrew Morton , Konrad Rzeszutek Wilk , Minchan Kim , Peter Zijlstra , "Paul E. McKenney" Subject: Re: [PATCH v11 4/7] mm: introduce compaction and migration for ballooned pages Message-ID: <20121109121602.GQ3886@csn.ul.ie> References: <08be4346b620ae9344691cc6c2ad0bc51f492e01.1352256088.git.aquini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <08be4346b620ae9344691cc6c2ad0bc51f492e01.1352256088.git.aquini@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5368 Lines: 159 On Wed, Nov 07, 2012 at 01:05:51AM -0200, Rafael Aquini wrote: > Memory fragmentation introduced by ballooning might reduce significantly > the number of 2MB contiguous memory blocks that can be used within a guest, > thus imposing performance penalties associated with the reduced number of > transparent huge pages that could be used by the guest workload. > > This patch introduces the helper functions as well as the necessary changes > to teach compaction and migration bits how to cope with pages which are > part of a guest memory balloon, in order to make them movable by memory > compaction procedures. > > Signed-off-by: Rafael Aquini > --- > mm/compaction.c | 21 +++++++++++++++++++-- > mm/migrate.c | 36 ++++++++++++++++++++++++++++++++++-- > 2 files changed, 53 insertions(+), 4 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 9eef558..76abd84 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -14,6 +14,7 @@ > #include > #include > #include > +#include > #include "internal.h" > > #if defined CONFIG_COMPACTION || defined CONFIG_CMA > @@ -565,9 +566,24 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, > goto next_pageblock; > } > > - /* Check may be lockless but that's ok as we recheck later */ > - if (!PageLRU(page)) > + /* > + * Check may be lockless but that's ok as we recheck later. > + * It's possible to migrate LRU pages and balloon pages > + * Skip any other type of page > + */ > + if (!PageLRU(page)) { > + if (unlikely(balloon_page_movable(page))) { Because it's lockless, it really seems that the barrier stuck down there is unnecessary. At worst you get a temporarily incorrect answer that you recheck later under page lock in balloon_page_isolate. > + if (locked && balloon_page_isolate(page)) { > + /* Successfully isolated */ > + cc->finished_update_migrate = true; > + list_add(&page->lru, migratelist); > + cc->nr_migratepages++; > + nr_isolated++; > + goto check_compact_cluster; > + } > + } > continue; > + } > > /* > * PageLRU is set. lru_lock normally excludes isolation > @@ -621,6 +637,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, > cc->nr_migratepages++; > nr_isolated++; > > +check_compact_cluster: > /* Avoid isolating too much */ > if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) { > ++low_pfn; > diff --git a/mm/migrate.c b/mm/migrate.c > index 98c7a89..87ffe54 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -35,6 +35,7 @@ > #include > #include > #include > +#include > > #include > > @@ -79,7 +80,10 @@ void putback_lru_pages(struct list_head *l) > list_del(&page->lru); > dec_zone_page_state(page, NR_ISOLATED_ANON + > page_is_file_cache(page)); > - putback_lru_page(page); > + if (unlikely(balloon_page_movable(page))) > + balloon_page_putback(page); > + else > + putback_lru_page(page); > } > } > > @@ -778,6 +782,18 @@ static int __unmap_and_move(struct page *page, struct page *newpage, > } > } > > + if (unlikely(balloon_page_movable(page))) { > + /* > + * A ballooned page does not need any special attention from > + * physical to virtual reverse mapping procedures. > + * Skip any attempt to unmap PTEs or to remap swap cache, > + * in order to avoid burning cycles at rmap level, and perform > + * the page migration right away (proteced by page lock). > + */ > + rc = balloon_page_migrate(newpage, page, mode); > + goto uncharge; > + } > + > /* > * Corner case handling: > * 1. When a new swap-cache page is read into, it is added to the LRU > @@ -814,7 +830,9 @@ skip_unmap: > put_anon_vma(anon_vma); > > uncharge: > - mem_cgroup_end_migration(mem, page, newpage, rc == MIGRATEPAGE_SUCCESS); > + mem_cgroup_end_migration(mem, page, newpage, > + (rc == MIGRATEPAGE_SUCCESS || > + rc == MIGRATEPAGE_BALLOON_SUCCESS)); > unlock: > unlock_page(page); > out: > @@ -846,6 +864,20 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, > goto out; > > rc = __unmap_and_move(page, newpage, force, offlining, mode); > + > + if (unlikely(rc == MIGRATEPAGE_BALLOON_SUCCESS)) { > + /* > + * A ballooned page has been migrated already. > + * Now, it's the time to remove the old page from the isolated > + * pageset list and handle it back to Buddy, wrap-up counters > + * and return. > + */ > + dec_zone_page_state(page, NR_ISOLATED_ANON + > + page_is_file_cache(page)); > + put_page(page); > + __free_page(page); > + return 0; > + } > out: > if (rc != -EAGAIN) { > /* It may be necessary to make this more generic for migration-related callbacks but I see nothing incompatible in your patch with doing that. Doing the abstraction now would be overkill so Acked-by: Mel Gorman -- Mel Gorman SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/