Creates a special function kmem_cache_isolate_slab() and kmem_cache_reclaim() to support lumpy reclaim. In order to isolate pages we will have to handle slab page allocations in such a way that we can determine if a slab is valid whenever we access it regardless of its time in life. A valid slab that can be freed has PageSlab(page) and page->inuse > 0 set. So we need to make sure in allocate_slab() that page->inuse is zero before PageSlab is set. kmem_cache_isolate_page() is called from lumpy reclaim to isolate pages neighboring a page cache page that is being reclaimed. Lumpy reclaim will gather the slabs and call kmem_cache_reclaim() on the list. This means that we can remove a slab in order to be able to coalesce a higher order page. Reviewed-by: Rik van Riel Signed-off-by: Christoph Lameter --- include/linux/slab.h | 2 + mm/slab.c | 13 ++++++ mm/slub.c | 102 ++++++++++++++++++++++++++++++++++++++++++++++++--- mm/vmscan.c | 13 +++++- 4 files changed, 123 insertions(+), 7 deletions(-) Index: linux-2.6/include/linux/slab.h =================================================================== --- linux-2.6.orig/include/linux/slab.h 2007-11-06 13:50:47.000000000 -0800 +++ linux-2.6/include/linux/slab.h 2007-11-06 13:50:54.000000000 -0800 @@ -64,6 +64,8 @@ unsigned int kmem_cache_size(struct kmem const char *kmem_cache_name(struct kmem_cache *); int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr); int kmem_cache_defrag(int node); +int kmem_cache_isolate_slab(struct page *); +int kmem_cache_reclaim(struct list_head *); /* * Please use this macro to create slab caches. Simply specify the Index: linux-2.6/mm/slab.c =================================================================== --- linux-2.6.orig/mm/slab.c 2007-11-06 13:50:33.000000000 -0800 +++ linux-2.6/mm/slab.c 2007-11-06 13:50:54.000000000 -0800 @@ -2559,6 +2559,19 @@ int kmem_cache_defrag(int node) return 0; } +/* + * SLAB does not support slab defragmentation + */ +int kmem_cache_isolate_slab(struct page *page) +{ + return -ENOSYS; +} + +int kmem_cache_reclaim(struct list_head *zaplist) +{ + return 0; +} + /** * kmem_cache_destroy - delete a cache * @cachep: the cache to destroy Index: linux-2.6/mm/slub.c =================================================================== --- linux-2.6.orig/mm/slub.c 2007-11-06 13:50:40.000000000 -0800 +++ linux-2.6/mm/slub.c 2007-11-06 13:50:54.000000000 -0800 @@ -1088,18 +1088,19 @@ static noinline struct page *new_slab(st page = allocate_slab(s, flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node); if (!page) - goto out; + return NULL; n = get_node(s, page_to_nid(page)); if (n) atomic_long_inc(&n->nr_slabs); + + page->inuse = 0; page->slab = s; - state = 1 << PG_slab; + state = page->flags | (1 << PG_slab); if (s->flags & (SLAB_DEBUG_FREE | SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | SLAB_TRACE)) state |= SLABDEBUG; - page->flags |= state; start = page_address(page); page->end = start + 1; @@ -1116,8 +1117,13 @@ static noinline struct page *new_slab(st set_freepointer(s, last, page->end); page->freelist = start; - page->inuse = 0; -out: + + /* + * page->inuse must be 0 when PageSlab(page) becomes + * true so that defrag knows that this slab is not in use. + */ + smp_wmb(); + page->flags = state; return page; } @@ -2622,6 +2628,92 @@ out: } #endif + +/* + * Check if the given state is that of a reclaimable slab page. + * + * This is only true if this is indeed a slab page and if + * the page has not been frozen. + */ +static inline int reclaimable_slab(unsigned long state) +{ + if (!(state & (1 << PG_slab))) + return 0; + + if (state & FROZEN) + return 0; + + return 1; +} + + /* + * Isolate page from the slab partial lists. Return 0 if succesful. + * + * After isolation the LRU field can be used to put the page onto + * a reclaim list. + */ +int kmem_cache_isolate_slab(struct page *page) +{ + unsigned long flags; + struct kmem_cache *s; + int rc = -ENOENT; + unsigned long state; + + /* + * Avoid attempting to isolate the slab pages if there are + * indications that this will not be successful. + */ + if (!reclaimable_slab(page->flags) || page_count(page) == 1) + return rc; + + /* + * Get a reference to the page. Return if its freed or being freed. + * This is necessary to make sure that the page does not vanish + * from under us before we are able to check the result. + */ + if (!get_page_unless_zero(page)) + return rc; + + local_irq_save(flags); + state = slab_lock(page); + + /* + * Check the flags again now that we have locked it. + */ + if (!reclaimable_slab(flags) || !page->inuse) { + slab_unlock(page, state); + put_page(page); + goto out; + } + + /* + * Drop reference count. There are object remaining and therefore + * the slab lock will have to be taken before the last object can + * be removed. We hold the slab lock, so no one can free this slab + * now. + * + * We set the slab frozen before releasing the lock. This means + * that no slab free action will be performed. If all objects are + * removed then the slab will be freed during kmem_cache_reclaim(). + */ + BUG_ON(page_count(page) <= 1); + put_page(page); + + /* + * Remove the slab from the lists and mark it frozen + */ + s = page->slab; + if (page->inuse < s->objects) + remove_partial(s, page); + else if (s->flags & SLAB_STORE_USER) + remove_full(s, page); + slab_unlock(page, state | FROZEN); + rc = 0; +out: + local_irq_restore(flags); + return rc; +} + /* * Conversion table for small slabs sizes / 8 to the index in the * kmalloc array. This is necessary for slabs < 192 since we have non power Index: linux-2.6/mm/vmscan.c =================================================================== --- linux-2.6.orig/mm/vmscan.c 2007-11-06 13:50:47.000000000 -0800 +++ linux-2.6/mm/vmscan.c 2007-11-06 13:50:54.000000000 -0800 @@ -687,6 +687,7 @@ static int __isolate_lru_page(struct pag */ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, struct list_head *src, struct list_head *dst, + struct list_head *slab_pages, unsigned long *scanned, int order, int mode) { unsigned long nr_taken = 0; @@ -760,7 +761,13 @@ static unsigned long isolate_lru_pages(u case -EBUSY: /* else it is being freed elsewhere */ list_move(&cursor_page->lru, src); + break; + default: + if (slab_pages && + kmem_cache_isolate_slab(cursor_page) == 0) + list_add(&cursor_page->lru, + slab_pages); break; } } @@ -796,6 +803,7 @@ static unsigned long shrink_inactive_lis struct zone *zone, struct scan_control *sc) { LIST_HEAD(page_list); + LIST_HEAD(slab_list); struct pagevec pvec; unsigned long nr_scanned = 0; unsigned long nr_reclaimed = 0; @@ -813,7 +821,7 @@ static unsigned long shrink_inactive_lis nr_taken = isolate_lru_pages(sc->swap_cluster_max, &zone->inactive_list, - &page_list, &nr_scan, sc->order, + &page_list, &slab_list, &nr_scan, sc->order, (sc->order > PAGE_ALLOC_COSTLY_ORDER)? ISOLATE_BOTH : ISOLATE_INACTIVE); nr_active = clear_active_flags(&page_list); @@ -824,6 +832,7 @@ static unsigned long shrink_inactive_lis -(nr_taken - nr_active)); zone->pages_scanned += nr_scan; spin_unlock_irq(&zone->lru_lock); + kmem_cache_reclaim(&slab_list); nr_scanned += nr_scan; nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC); @@ -1029,7 +1038,7 @@ force_reclaim_mapped: lru_add_drain(); spin_lock_irq(&zone->lru_lock); pgmoved = isolate_lru_pages(nr_pages, &zone->active_list, - &l_hold, &pgscanned, sc->order, ISOLATE_ACTIVE); + &l_hold, NULL, &pgscanned, sc->order, ISOLATE_ACTIVE); zone->pages_scanned += pgscanned; __mod_zone_page_state(zone, NR_ACTIVE, -pgmoved); spin_unlock_irq(&zone->lru_lock); -- - 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/