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 <aqu...@redhat.com> 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 <aqu...@redhat.com> > > --- > > 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 <linux/backing-dev.h> > > #include <linux/sysctl.h> > > #include <linux/sysfs.h> > > +#include <linux/export.h> > > #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 majord...@kvack.org. For more info on Linux MM, > > see: http://www.linux-mm.org/ . > > Don't email: <a href=mailto:"d...@kvack.org"> em...@kvack.org </a> > > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization