From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f53.google.com (mail-pa0-f53.google.com [209.85.220.53]) by kanga.kvack.org (Postfix) with ESMTP id 480B32802A5 for ; Mon, 6 Jul 2015 08:19:21 -0400 (EDT) Received: by pactm7 with SMTP id tm7so94865916pac.2 for ; Mon, 06 Jul 2015 05:19:21 -0700 (PDT) Received: from mail-pd0-x236.google.com (mail-pd0-x236.google.com. [2607:f8b0:400e:c02::236]) by mx.google.com with ESMTPS id qp7si28838029pac.120.2015.07.06.05.19.20 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 06 Jul 2015 05:19:20 -0700 (PDT) Received: by pdbci14 with SMTP id ci14so105265930pdb.2 for ; Mon, 06 Jul 2015 05:19:19 -0700 (PDT) From: Sergey Senozhatsky Subject: [PATCH v5 7/7] zsmalloc: register a shrinker to trigger auto-compaction Date: Mon, 6 Jul 2015 21:17:50 +0900 Message-Id: <1436185070-1940-8-git-send-email-sergey.senozhatsky@gmail.com> In-Reply-To: <1436185070-1940-1-git-send-email-sergey.senozhatsky@gmail.com> References: <1436185070-1940-1-git-send-email-sergey.senozhatsky@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sergey@kvack.org, "Senozhatsky Perform automatic pool compaction by a shrinker when system is getting tight on memory. User-space has a very little knowledge regarding zsmalloc fragmentation and basically has no mechanism to tell whether compaction will result in any memory gain. Another issue is that user space is not always aware of the fact that system is getting tight on memory. Which leads to very uncomfortable scenarios when user space may start issuing compaction 'randomly' or from crontab (for example). Fragmentation is not always necessarily bad, allocated and unused objects, after all, may be filled with the data later, w/o the need of allocating a new zspage. On the other hand, we obviously don't want to waste memory when the system needs it. Compaction now has a relatively quick pool scan so we are able to estimate the number of pages that will be freed easily, which makes it possible to call this function from a shrinker->count_objects() callback. We also abort compaction as soon as we detect that we can't free any pages any more, preventing wasteful objects migrations. Minchan Kim proposed to use the shrinker (the original patch was too aggressive and was attempting to perform compaction for every ALMOST_EMPTY zspage). Signed-off-by: Sergey Senozhatsky Suggested-by: Minchan Kim --- mm/zsmalloc.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 73 insertions(+), 1 deletion(-) diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index a761733..e557c16 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -247,7 +247,9 @@ struct zs_pool { atomic_long_t pages_allocated; /* How many pages were migrated (freed) */ unsigned long num_migrated; - + /* Compact classes */ + struct shrinker shrinker; + bool shrinker_enabled; #ifdef CONFIG_ZSMALLOC_STAT struct dentry *stat_dentry; #endif @@ -1787,6 +1789,69 @@ unsigned long zs_compact(struct zs_pool *pool) } EXPORT_SYMBOL_GPL(zs_compact); +static unsigned long zs_shrinker_scan(struct shrinker *shrinker, + struct shrink_control *sc) +{ + unsigned long pages_freed; + struct zs_pool *pool = container_of(shrinker, struct zs_pool, + shrinker); + + pages_freed = pool->num_migrated; + /* + * Compact classes and calculate compaction delta. + * Can run concurrently with a manually triggered + * (by user) compaction. + */ + pages_freed = zs_compact(pool) - pages_freed; + + return pages_freed ? pages_freed : SHRINK_STOP; +} + +static unsigned long zs_shrinker_count(struct shrinker *shrinker, + struct shrink_control *sc) +{ + int i; + struct size_class *class; + unsigned long pages_to_free = 0; + struct zs_pool *pool = container_of(shrinker, struct zs_pool, + shrinker); + + if (!pool->shrinker_enabled) + return 0; + + for (i = zs_size_classes - 1; i >= 0; i--) { + class = pool->size_class[i]; + if (!class) + continue; + if (class->index != i) + continue; + + spin_lock(&class->lock); + pages_to_free += zs_can_compact(class); + spin_unlock(&class->lock); + } + + return pages_to_free; +} + +static void zs_unregister_shrinker(struct zs_pool *pool) +{ + if (pool->shrinker_enabled) { + unregister_shrinker(&pool->shrinker); + pool->shrinker_enabled = false; + } +} + +static int zs_register_shrinker(struct zs_pool *pool) +{ + pool->shrinker.scan_objects = zs_shrinker_scan; + pool->shrinker.count_objects = zs_shrinker_count; + pool->shrinker.batch = 0; + pool->shrinker.seeks = DEFAULT_SEEKS; + + return register_shrinker(&pool->shrinker); +} + /** * zs_create_pool - Creates an allocation pool to work from. * @flags: allocation flags used to allocate pool metadata @@ -1872,6 +1937,12 @@ struct zs_pool *zs_create_pool(char *name, gfp_t flags) if (zs_pool_stat_create(name, pool)) goto err; + /* + * Not critical, we still can use the pool + * and user can trigger compaction manually. + */ + if (zs_register_shrinker(pool) == 0) + pool->shrinker_enabled = true; return pool; err: @@ -1884,6 +1955,7 @@ void zs_destroy_pool(struct zs_pool *pool) { int i; + zs_unregister_shrinker(pool); zs_pool_stat_destroy(pool); for (i = 0; i < zs_size_classes; i++) { -- 2.5.0.rc0.3.g912bd49 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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