Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757973Ab2FYX6j (ORCPT ); Mon, 25 Jun 2012 19:58:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41073 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757262Ab2FYX6h (ORCPT ); Mon, 25 Jun 2012 19:58:37 -0400 Date: Mon, 25 Jun 2012 20:57:40 -0300 From: Rafael Aquini To: Konrad Rzeszutek Wilk Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Rusty Russell , "Michael S. Tsirkin" , Rik van Riel Subject: Re: [PATCH 1/4] mm: introduce compaction and migration for virtio ballooned pages Message-ID: <20120625235739.GA1887@t510.redhat.com> References: <7f83427b3894af7969c67acc0f27ab5aa68b4279.1340665087.git.aquini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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: 9289 Lines: 220 On Mon, Jun 25, 2012 at 07:31:38PM -0400, Konrad Rzeszutek Wilk wrote: > On Mon, Jun 25, 2012 at 7:25 PM, Rafael Aquini wrote: > > This patch introduces helper functions that 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. > > > > Should the names that are exported be prefixed with kvm_? > I rather let them as generic as possible, specially because I believe other balloon drivers can leverage the same technique to make their page lists movable as well, in the near future. However, I do agree with your tip if we ended up finding out no one else can reuse this piece of code. > > Signed-off-by: Rafael Aquini > > --- > > ?include/linux/mm.h | ? 17 +++++++++++++ > > ?mm/compaction.c ? ?| ? 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > > ?mm/migrate.c ? ? ? | ? 30 +++++++++++++++++++++- > > ?3 files changed, 118 insertions(+), 1 deletion(-) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index b36d08c..360656e 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -1629,5 +1629,22 @@ static inline unsigned int debug_guardpage_minorder(void) { return 0; } > > ?static inline bool page_is_guard(struct page *page) { return false; } > > ?#endif /* CONFIG_DEBUG_PAGEALLOC */ > > > > +#if (defined(CONFIG_VIRTIO_BALLOON) || \ > > + ? ? ? defined(CONFIG_VIRTIO_BALLOON_MODULE)) && defined(CONFIG_COMPACTION) > > +extern int is_balloon_page(struct page *); > > +extern int isolate_balloon_page(struct page *); > > +extern int putback_balloon_page(struct page *); > > + > > +/* return 1 if page is part of a guest's memory balloon, 0 otherwise */ > > +static inline int PageBalloon(struct page *page) > > +{ > > + ? ? ? return is_balloon_page(page); > > +} > > +#else > > +static inline int PageBalloon(struct page *page) ? ? ? ? ? ? ? { return 0; } > > +static inline int isolate_balloon_page(struct page *page) ? ? ?{ return 0; } > > +static inline int putback_balloon_page(struct page *page) ? ? ?{ return 0; } > > +#endif /* (VIRTIO_BALLOON || VIRTIO_BALLOON_MODULE) && COMPACTION */ > > + > > ?#endif /* __KERNEL__ */ > > ?#endif /* _LINUX_MM_H */ > > diff --git a/mm/compaction.c b/mm/compaction.c > > index 7ea259d..8835d55 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 > > @@ -312,6 +313,14 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, > > ? ? ? ? ? ? ? ? ? ? ? ?continue; > > ? ? ? ? ? ? ? ?} > > > > + ? ? ? ? ? ? ? /* > > + ? ? ? ? ? ? ? ?* For ballooned pages, we need to isolate them before testing > > + ? ? ? ? ? ? ? ?* for PageLRU, as well as skip the LRU page isolation steps. > > + ? ? ? ? ? ? ? ?*/ > > + ? ? ? ? ? ? ? if (PageBalloon(page)) > > + ? ? ? ? ? ? ? ? ? ? ? if (isolate_balloon_page(page)) > > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? goto isolated_balloon_page; > > + > > ? ? ? ? ? ? ? ?if (!PageLRU(page)) > > ? ? ? ? ? ? ? ? ? ? ? ?continue; > > > > @@ -338,6 +347,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, > > > > ? ? ? ? ? ? ? ?/* Successfully isolated */ > > ? ? ? ? ? ? ? ?del_page_from_lru_list(page, lruvec, page_lru(page)); > > +isolated_balloon_page: > > ? ? ? ? ? ? ? ?list_add(&page->lru, migratelist); > > ? ? ? ? ? ? ? ?cc->nr_migratepages++; > > ? ? ? ? ? ? ? ?nr_isolated++; > > @@ -903,4 +913,66 @@ void compaction_unregister_node(struct node *node) > > ?} > > ?#endif /* CONFIG_SYSFS && CONFIG_NUMA */ > > > > +#if defined(CONFIG_VIRTIO_BALLOON) || defined(CONFIG_VIRTIO_BALLOON_MODULE) > > +/* > > + * Balloon pages special page->mapping. > > + * users must properly allocate and initiliaze an instance of balloon_mapping, > > + * and set it as the page->mapping for balloon enlisted page instances. > > + * > > + * address_space_operations necessary methods for ballooned pages: > > + * ? .migratepage ? ?- used to perform balloon's page migration (as is) > > + * ? .invalidatepage - used to isolate a page from balloon's page list > > + * ? .freepage ? ? ? - used to reinsert an isolated page to balloon's page list > > + */ > > +struct address_space *balloon_mapping; > > +EXPORT_SYMBOL(balloon_mapping); > > + > > +/* ballooned page id check */ > > +int is_balloon_page(struct page *page) > > +{ > > + ? ? ? struct address_space *mapping = page->mapping; > > + ? ? ? if (mapping == balloon_mapping) > > + ? ? ? ? ? ? ? return 1; > > + ? ? ? return 0; > > +} > > + > > +/* __isolate_lru_page() counterpart for a ballooned page */ > > +int isolate_balloon_page(struct page *page) > > +{ > > + ? ? ? struct address_space *mapping = page->mapping; > > + ? ? ? if (mapping->a_ops->invalidatepage) { > > + ? ? ? ? ? ? ? /* > > + ? ? ? ? ? ? ? ?* We can race against move_to_new_page() and stumble across a > > + ? ? ? ? ? ? ? ?* locked 'newpage'. If we succeed on isolating it, the result > > + ? ? ? ? ? ? ? ?* tends to be disastrous. So, we sanely skip PageLocked here. > > + ? ? ? ? ? ? ? ?*/ > > + ? ? ? ? ? ? ? if (likely(!PageLocked(page) && get_page_unless_zero(page))) { > > + ? ? ? ? ? ? ? ? ? ? ? /* > > + ? ? ? ? ? ? ? ? ? ? ? ?* A ballooned page, by default, has just one refcount. > > + ? ? ? ? ? ? ? ? ? ? ? ?* Prevent concurrent compaction threads from isolating > > + ? ? ? ? ? ? ? ? ? ? ? ?* an already isolated balloon page. > > + ? ? ? ? ? ? ? ? ? ? ? ?*/ > > + ? ? ? ? ? ? ? ? ? ? ? if (page_count(page) == 2) { > > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? mapping->a_ops->invalidatepage(page, 0); > > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? return 1; > > + ? ? ? ? ? ? ? ? ? ? ? } > > + ? ? ? ? ? ? ? ? ? ? ? /* Drop refcount taken for this already isolated page */ > > + ? ? ? ? ? ? ? ? ? ? ? put_page(page); > > + ? ? ? ? ? ? ? } > > + ? ? ? } > > + ? ? ? return 0; > > +} > > + > > +/* putback_lru_page() counterpart for a ballooned page */ > > +int putback_balloon_page(struct page *page) > > +{ > > + ? ? ? struct address_space *mapping = page->mapping; > > + ? ? ? if (mapping->a_ops->freepage) { > > + ? ? ? ? ? ? ? mapping->a_ops->freepage(page); > > + ? ? ? ? ? ? ? put_page(page); > > + ? ? ? ? ? ? ? return 1; > > + ? ? ? } > > + ? ? ? return 0; > > +} > > +#endif /* CONFIG_VIRTIO_BALLOON || CONFIG_VIRTIO_BALLOON_MODULE */ > > ?#endif /* CONFIG_COMPACTION */ > > diff --git a/mm/migrate.c b/mm/migrate.c > > index be26d5c..ffc02a4 100644 > > --- a/mm/migrate.c > > +++ b/mm/migrate.c > > @@ -78,7 +78,10 @@ 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(PageBalloon(page))) > > + ? ? ? ? ? ? ? ? ? ? ? VM_BUG_ON(!putback_balloon_page(page)); > > + ? ? ? ? ? ? ? else > > + ? ? ? ? ? ? ? ? ? ? ? putback_lru_page(page); > > ? ? ? ?} > > ?} > > > > @@ -783,6 +786,17 @@ static int __unmap_and_move(struct page *page, struct page *newpage, > > ? ? ? ? ? ? ? ?} > > ? ? ? ?} > > > > + ? ? ? if (PageBalloon(page)) { > > + ? ? ? ? ? ? ? /* > > + ? ? ? ? ? ? ? ?* A ballooned page does not need any special attention from > > + ? ? ? ? ? ? ? ?* physical to virtual reverse mapping procedures. > > + ? ? ? ? ? ? ? ?* To avoid burning cycles at rmap level, > > + ? ? ? ? ? ? ? ?* skip attempts to unmap PTEs or remap swapcache. > > + ? ? ? ? ? ? ? ?*/ > > + ? ? ? ? ? ? ? remap_swapcache = 0; > > + ? ? ? ? ? ? ? goto skip_unmap; > > + ? ? ? } > > + > > ? ? ? ?/* > > ? ? ? ? * Corner case handling: > > ? ? ? ? * 1. When a new swap-cache page is read into, it is added to the LRU > > @@ -852,6 +866,20 @@ 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 (PageBalloon(newpage)) { > > + ? ? ? ? ? ? ? /* > > + ? ? ? ? ? ? ? ?* A ballooned page has been migrated already. Now, it is the > > + ? ? ? ? ? ? ? ?* time to wrap-up counters, handle the old page back to Buddy > > + ? ? ? ? ? ? ? ?* and return. > > + ? ? ? ? ? ? ? ?*/ > > + ? ? ? ? ? ? ? list_del(&page->lru); > > + ? ? ? ? ? ? ? dec_zone_page_state(page, NR_ISOLATED_ANON + > > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? page_is_file_cache(page)); > > + ? ? ? ? ? ? ? put_page(page); > > + ? ? ? ? ? ? ? __free_page(page); > > + ? ? ? ? ? ? ? return rc; > > + ? ? ? } > > ?out: > > ? ? ? ?if (rc != -EAGAIN) { > > ? ? ? ? ? ? ? ?/* > > -- > > 1.7.10.2 > > > > -- > > 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 > > -- 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/