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Thu, 17 Nov 2022 14:48:30 -0800 (PST) Date: Thu, 17 Nov 2022 14:48:28 -0800 From: Minchan Kim To: Nhat Pham Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ngupta@vflare.org, senozhatsky@chromium.org, sjenning@redhat.com, ddstreet@ieee.org, vitaly.wool@konsulko.com Subject: Re: [PATCH v4 5/5] zsmalloc: Implement writeback mechanism for zsmalloc Message-ID: References: <20221117163839.230900-1-nphamcs@gmail.com> <20221117163839.230900-6-nphamcs@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221117163839.230900-6-nphamcs@gmail.com> ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668725311; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; 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dkim=pass header.d=gmail.com header.s=20210112 header.b=VZDZ3+yp; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=kernel.org (policy=none); spf=pass (imf26.hostedemail.com: domain of minchan.kim@gmail.com designates 209.85.215.180 as permitted sender) smtp.mailfrom=minchan.kim@gmail.com X-Rspamd-Server: rspam07 X-HE-Tag: 1668725311-418363 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Nov 17, 2022 at 08:38:39AM -0800, Nhat Pham wrote: > This commit adds the writeback mechanism for zsmalloc, analogous to the > zbud allocator. Zsmalloc will attempt to determine the coldest zspage > (i.e least recently used) in the pool, and attempt to write back all the > stored compressed objects via the pool's evict handler. > > Signed-off-by: Nhat Pham > --- > mm/zsmalloc.c | 203 +++++++++++++++++++++++++++++++++++++++++++++----- > 1 file changed, 184 insertions(+), 19 deletions(-) > > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c > index 776d0e15a401..0ab9f173e964 100644 > --- a/mm/zsmalloc.c > +++ b/mm/zsmalloc.c > @@ -280,10 +280,13 @@ struct zspage { > struct list_head lru; > #endif > > + bool under_reclaim; > + > + /* list of unfreed handles whose objects have been reclaimed */ > + unsigned long *deferred_handles; > + Guess we don't need to bloat the zspage on !CONFIG_ZPOOL? > struct zs_pool *pool; > -#ifdef CONFIG_COMPACTION > rwlock_t lock; > -#endif > }; > > struct mapping_area { > @@ -304,10 +307,11 @@ static bool ZsHugePage(struct zspage *zspage) > return zspage->huge; > } > > -#ifdef CONFIG_COMPACTION > static void migrate_lock_init(struct zspage *zspage); > static void migrate_read_lock(struct zspage *zspage); > static void migrate_read_unlock(struct zspage *zspage); > + > +#ifdef CONFIG_COMPACTION > static void migrate_write_lock(struct zspage *zspage); > static void migrate_write_lock_nested(struct zspage *zspage); > static void migrate_write_unlock(struct zspage *zspage); > @@ -315,9 +319,6 @@ static void kick_deferred_free(struct zs_pool *pool); > static void init_deferred_free(struct zs_pool *pool); > static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage); > #else > -static void migrate_lock_init(struct zspage *zspage) {} > -static void migrate_read_lock(struct zspage *zspage) {} > -static void migrate_read_unlock(struct zspage *zspage) {} > static void migrate_write_lock(struct zspage *zspage) {} > static void migrate_write_lock_nested(struct zspage *zspage) {} > static void migrate_write_unlock(struct zspage *zspage) {} > @@ -449,6 +450,27 @@ static void zs_zpool_free(void *pool, unsigned long handle) > zs_free(pool, handle); > } > > +static int zs_reclaim_page(struct zs_pool *pool, unsigned int retries); > + > +static int zs_zpool_shrink(void *pool, unsigned int pages, what pages? > + unsigned int *reclaimed) > +{ > + unsigned int total = 0; > + int ret = -EINVAL; > + > + while (total < pages) { > + ret = zs_reclaim_page(pool, 8); > + if (ret < 0) > + break; > + total++; > + } > + > + if (reclaimed) > + *reclaimed = total; > + > + return ret; > +} > + > static void *zs_zpool_map(void *pool, unsigned long handle, > enum zpool_mapmode mm) > { > @@ -487,6 +509,7 @@ static struct zpool_driver zs_zpool_driver = { > .malloc_support_movable = true, > .malloc = zs_zpool_malloc, > .free = zs_zpool_free, > + .shrink = zs_zpool_shrink, > .map = zs_zpool_map, > .unmap = zs_zpool_unmap, > .total_size = zs_zpool_total_size, > @@ -960,6 +983,21 @@ static int trylock_zspage(struct zspage *zspage) > return 0; > } > > +/* > + * Free all the deferred handles whose objects are freed in zs_free. > + */ > +static void free_handles(struct zs_pool *pool, struct zspage *zspage) > +{ > + unsigned long handle = (unsigned long)zspage->deferred_handles; > + > + while (handle) { > + unsigned long nxt_handle = handle_to_obj(handle); > + > + cache_free_handle(pool, handle); > + handle = nxt_handle; > + } > +} > + Shouldn't we have it under CONFIG_ZPOOL? > static void __free_zspage(struct zs_pool *pool, struct size_class *class, > struct zspage *zspage) > { > @@ -974,6 +1012,9 @@ static void __free_zspage(struct zs_pool *pool, struct size_class *class, > VM_BUG_ON(get_zspage_inuse(zspage)); > VM_BUG_ON(fg != ZS_EMPTY); > > + /* Free all deferred handles from zs_free */ > + free_handles(pool, zspage); > + > next = page = get_first_page(zspage); > do { > VM_BUG_ON_PAGE(!PageLocked(page), page); > @@ -1060,6 +1101,8 @@ static void init_zspage(struct size_class *class, struct zspage *zspage) > #ifdef CONFIG_ZPOOL > INIT_LIST_HEAD(&zspage->lru); > #endif > + zspage->under_reclaim = false; > + zspage->deferred_handles = NULL; > > set_freeobj(zspage, 0); > } > @@ -1482,13 +1525,7 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp) > record_obj(handle, obj); > class_stat_inc(class, OBJ_USED, 1); > > -#ifdef CONFIG_ZPOOL > - /* Move the zspage to front of pool's LRU */ > - move_to_front(pool, zspage); > -#endif > - spin_unlock(&pool->lock); > - > - return handle; > + goto out; This chunk should go in "Add a LRU to zs_pool to keep track of zspages in LRU order" > } > > spin_unlock(&pool->lock); > @@ -1512,12 +1549,12 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp) > > /* We completely set up zspage so mark them as movable */ > SetZsPageMovable(pool, zspage); > +out: > #ifdef CONFIG_ZPOOL > /* Move the zspage to front of pool's LRU */ > move_to_front(pool, zspage); > #endif > spin_unlock(&pool->lock); > - Unnecessary change. > return handle; > } > EXPORT_SYMBOL_GPL(zs_malloc); > @@ -1571,12 +1608,24 @@ void zs_free(struct zs_pool *pool, unsigned long handle) > > obj_free(class->size, obj); > class_stat_dec(class, OBJ_USED, 1); > + > + if (zspage->under_reclaim) { > + /* > + * Reclaim needs the handles during writeback. It'll free > + * them along with the zspage when it's done with them. > + * > + * Record current deferred handle at the memory location > + * whose address is given by handle. > + */ > + record_obj(handle, (unsigned long)zspage->deferred_handles); > + zspage->deferred_handles = (unsigned long *)handle; > + spin_unlock(&pool->lock); > + return; > + } > fullness = fix_fullness_group(class, zspage); > - if (fullness != ZS_EMPTY) > - goto out; > + if (fullness == ZS_EMPTY) > + free_zspage(pool, class, zspage); > > - free_zspage(pool, class, zspage); > -out: > spin_unlock(&pool->lock); > cache_free_handle(pool, handle); > } > @@ -1776,7 +1825,7 @@ static enum fullness_group putback_zspage(struct size_class *class, > return fullness; > } > > -#ifdef CONFIG_COMPACTION > +#if defined(CONFIG_ZPOOL) || defined(CONFIG_COMPACTION) > /* > * To prevent zspage destroy during migration, zspage freeing should > * hold locks of all pages in the zspage. > @@ -1818,6 +1867,24 @@ static void lock_zspage(struct zspage *zspage) > } > migrate_read_unlock(zspage); > } > +#endif /* defined(CONFIG_ZPOOL) || defined(CONFIG_COMPACTION) */ > + > +#ifdef CONFIG_ZPOOL > +/* > + * Unlocks all the pages of the zspage. > + * > + * pool->lock must be held before this function is called > + * to prevent the underlying pages from migrating. > + */ > +static void unlock_zspage(struct zspage *zspage) > +{ > + struct page *page = get_first_page(zspage); > + > + do { > + unlock_page(page); > + } while ((page = get_next_page(page)) != NULL); > +} > +#endif /* CONFIG_ZPOOL */ > > static void migrate_lock_init(struct zspage *zspage) > { > @@ -1834,6 +1901,7 @@ static void migrate_read_unlock(struct zspage *zspage) __releases(&zspage->lock) > read_unlock(&zspage->lock); > } > > +#ifdef CONFIG_COMPACTION > static void migrate_write_lock(struct zspage *zspage) > { > write_lock(&zspage->lock); > @@ -2398,6 +2466,103 @@ void zs_destroy_pool(struct zs_pool *pool) > } > EXPORT_SYMBOL_GPL(zs_destroy_pool); > > +#ifdef CONFIG_ZPOOL > +static int zs_reclaim_page(struct zs_pool *pool, unsigned int retries) > +{ > + int i, obj_idx, ret = 0; > + unsigned long handle; > + struct zspage *zspage; > + struct page *page; > + enum fullness_group fullness; > + > + if (retries == 0 || !pool->ops || !pool->ops->evict) > + return -EINVAL; > + > + /* Lock LRU and fullness list */ > + spin_lock(&pool->lock); > + if (list_empty(&pool->lru)) { > + spin_unlock(&pool->lock); > + return -EINVAL; > + } > + > + for (i = 0; i < retries; i++) { > + struct size_class *class; > + > + zspage = list_last_entry(&pool->lru, struct zspage, lru); > + list_del(&zspage->lru); > + > + /* zs_free may free objects, but not the zspage and handles */ > + zspage->under_reclaim = true; > + > + class = zspage_class(pool, zspage); > + fullness = get_fullness_group(class, zspage); > + > + /* Lock out object allocations and object compaction */ > + remove_zspage(class, zspage, fullness); > + > + spin_unlock(&pool->lock); > + > + /* Lock backing pages into place */ > + lock_zspage(zspage); > + > + obj_idx = 0; > + page = zspage->first_page; > + while (1) { > + handle = find_alloced_obj(class, page, &obj_idx); > + if (!handle) { > + page = get_next_page(page); > + if (!page) > + break; > + obj_idx = 0; > + continue; > + } > + > + /* > + * This will write the object and call > + * zs_free. You want to write in the same line. > + * > + * zs_free will free the object, but the > + * under_reclaim flag prevents it from freeing > + * the zspage altogether. This is necessary so > + * that we can continue working with the > + * zspage potentially after the last object > + * has been freed. > + */ > + ret = pool->ops->evict(pool, handle); > + if (ret) > + goto next; > + > + obj_idx++; > + } > + > +next: > + /* For freeing the zspage, or putting it back in the pool and LRU list. */ > + spin_lock(&pool->lock); > + zspage->under_reclaim = false; > + > + if (!get_zspage_inuse(zspage)) { > + /* > + * Fullness went stale as zs_free() won't touch it > + * while the page is removed from the pool. Fix it > + * up for the check in __free_zspage(). > + */ > + zspage->fullness = ZS_EMPTY; > + > + __free_zspage(pool, class, zspage); > + spin_unlock(&pool->lock); > + return 0; > + } > + > + putback_zspage(class, zspage); > + list_add(&zspage->lru, &pool->lru); > + unlock_zspage(zspage); > + } > + > + spin_unlock(&pool->lock); > + return -EAGAIN; > +} > +#endif /* CONFIG_ZPOOL */ > + > static int __init zs_init(void) > { > int ret; > -- > 2.30.2