From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id C0F136B0069 for ; Tue, 21 Nov 2017 09:18:18 -0500 (EST) Received: by mail-pf0-f198.google.com with SMTP id 82so11819278pfp.5 for ; Tue, 21 Nov 2017 06:18:18 -0800 (PST) Received: from mailout1.samsung.com (mailout1.samsung.com. [203.254.224.24]) by mx.google.com with ESMTPS id m23si11319786pfg.16.2017.11.21.06.18.16 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 21 Nov 2017 06:18:17 -0800 (PST) Received: from epcas5p1.samsung.com (unknown [182.195.41.39]) by mailout1.samsung.com (KnoxPortal) with ESMTP id 20171121141814epoutp0103abb6d9b51e48a0af444227f8227e6f~5H5mY_mOW1765817658epoutp01W for ; Tue, 21 Nov 2017 14:18:14 +0000 (GMT) Mime-Version: 1.0 Subject: [PATCH v2] zswap: Same-filled pages handling Reply-To: srividya.dr@samsung.com From: Srividya Desireddy In-Reply-To: <20171120154648.6c2f96804c4c1668bd8d572a@linux-foundation.org> Message-ID: <20171121141812epcms5p4d6dac642cedef6c811fdc67fca490804@epcms5p4> Date: Tue, 21 Nov 2017 14:18:12 +0000 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" References: <20171120154648.6c2f96804c4c1668bd8d572a@linux-foundation.org> <20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p1> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , "sjenning@redhat.com" , "ddstreet@ieee.org" , "linux-mm@kvack.org" , "willy@infradead.org" , "linux-kernel@vger.kernel.org" , "nefelim4ag@gmail.com" , "penberg@kernel.org" Cc: Dinakar Reddy Pathireddy , SHARAN ALLUR , RAJIB BASU , JUHUN KIM , "srividya.desireddy@gmail.com" , Srividya Desireddy , "Sangamanatha ." From: Srividya Desireddy Date: Sat, 18 Nov 2017 18:29:16 +0530 Subject: [PATCH v2] zswap: Same-filled pages handling Changes since v1 : Added memset_l instead of for loop. Zswap is a cache which compresses the pages that are being swapped out and stores them into a dynamically allocated RAM-based memory pool. Experiments have shown that around 10-20% of pages stored in zswap are same-filled pages (i.e. contents of the page are all same), but these pages are handled as normal pages by compressing and allocating memory in the pool. This patch adds a check in zswap_frontswap_store() to identify same-filled page before compression of the page. If the page is a same-filled page, set zswap_entry.length to zero, save the same-filled value and skip the compression of the page and alloction of memory in zpool. In zswap_frontswap_load(), check if value of zswap_entry.length is zero corresponding to the page to be loaded. If zswap_entry.length is zero, fill the page with same-filled value. This saves the decompression time during load. On a ARM Quad Core 32-bit device with 1.5GB RAM by launching and relaunching different applications, out of ~64000 pages stored in zswap, ~11000 pages were same-value filled pages (including zero-filled pages) and ~9000 pages were zero-filled pages. An average of 17% of pages(including zero-filled pages) in zswap are same-value filled pages and 14% pages are zero-filled pages. An average of 3% of pages are same-filled non-zero pages. The below table shows the execution time profiling with the patch. Baseline With patch % Improvement ----------------------------------------------------------------- *Zswap Store Time 26.5ms 18ms 32% (of same value pages) *Zswap Load Time (of same value pages) 25.5ms 13ms 49% ----------------------------------------------------------------- On Ubuntu PC with 2GB RAM, while executing kernel build and other test scripts and running multimedia applications, out of 360000 pages stored in zswap 78000(~22%) of pages were found to be same-value filled pages (including zero-filled pages) and 64000(~17%) are zero-filled pages. So an average of %5 of pages are same-filled non-zero pages. The below table shows the execution time profiling with the patch. Baseline With patch % Improvement ----------------------------------------------------------------- *Zswap Store Time 91ms 74ms 19% (of same value pages) *Zswap Load Time 50ms 7.5ms 85% (of same value pages) ----------------------------------------------------------------- *The execution times may vary with test device used. Signed-off-by: Srividya Desireddy --- mm/zswap.c | 71 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 66 insertions(+), 5 deletions(-) diff --git a/mm/zswap.c b/mm/zswap.c index d39581a..1133b4ce 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -49,6 +49,8 @@ static u64 zswap_pool_total_size; /* The number of compressed pages currently stored in zswap */ static atomic_t zswap_stored_pages = ATOMIC_INIT(0); +/* The number of same-value filled pages currently stored in zswap */ +static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0); /* * The statistics below are not protected from concurrent access for @@ -116,6 +118,11 @@ module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644); static unsigned int zswap_max_pool_percent = 20; module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644); +/* Enable/disable handling same-value filled pages (enabled by default) */ +static bool zswap_same_filled_pages_enabled = true; +module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled, + bool, 0644); + /********************************* * data structures **********************************/ @@ -145,9 +152,10 @@ struct zswap_pool { * be held while changing the refcount. Since the lock must * be held, there is no reason to also make refcount atomic. * length - the length in bytes of the compressed page data. Needed during - * decompression + * decompression. For a same value filled page length is 0. * pool - the zswap_pool the entry's data is in * handle - zpool allocation handle that stores the compressed page data + * value - value of the same-value filled pages which have same content */ struct zswap_entry { struct rb_node rbnode; @@ -155,7 +163,10 @@ struct zswap_entry { int refcount; unsigned int length; struct zswap_pool *pool; - unsigned long handle; + union { + unsigned long handle; + unsigned long value; + }; }; struct zswap_header { @@ -320,8 +331,12 @@ static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry) */ static void zswap_free_entry(struct zswap_entry *entry) { - zpool_free(entry->pool->zpool, entry->handle); - zswap_pool_put(entry->pool); + if (!entry->length) + atomic_dec(&zswap_same_filled_pages); + else { + zpool_free(entry->pool->zpool, entry->handle); + zswap_pool_put(entry->pool); + } zswap_entry_cache_free(entry); atomic_dec(&zswap_stored_pages); zswap_update_total_size(); @@ -953,6 +968,28 @@ static int zswap_shrink(void) return ret; } +static int zswap_is_page_same_filled(void *ptr, unsigned long *value) +{ + unsigned int pos; + unsigned long *page; + + page = (unsigned long *)ptr; + for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) { + if (page[pos] != page[0]) + return 0; + } + *value = page[0]; + return 1; +} + +static void zswap_fill_page(void *ptr, unsigned long value) +{ + unsigned long *page; + + page = (unsigned long *)ptr; + memset_l(page, value, PAGE_SIZE / sizeof(unsigned long)); +} + /********************************* * frontswap hooks **********************************/ @@ -965,7 +1002,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset, struct crypto_comp *tfm; int ret; unsigned int dlen = PAGE_SIZE, len; - unsigned long handle; + unsigned long handle, value; char *buf; u8 *src, *dst; struct zswap_header *zhdr; @@ -993,6 +1030,19 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset, goto reject; } + if (zswap_same_filled_pages_enabled) { + src = kmap_atomic(page); + if (zswap_is_page_same_filled(src, &value)) { + kunmap_atomic(src); + entry->offset = offset; + entry->length = 0; + entry->value = value; + atomic_inc(&zswap_same_filled_pages); + goto insert_entry; + } + kunmap_atomic(src); + } + /* if entry is successfully added, it keeps the reference */ entry->pool = zswap_pool_current_get(); if (!entry->pool) { @@ -1037,6 +1087,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset, entry->handle = handle; entry->length = dlen; +insert_entry: /* map */ spin_lock(&tree->lock); do { @@ -1089,6 +1140,13 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset, } spin_unlock(&tree->lock); + if (!entry->length) { + dst = kmap_atomic(page); + zswap_fill_page(dst, entry->value); + kunmap_atomic(dst); + goto freeentry; + } + /* decompress */ dlen = PAGE_SIZE; src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle, @@ -1101,6 +1159,7 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset, zpool_unmap_handle(entry->pool->zpool, entry->handle); BUG_ON(ret); +freeentry: spin_lock(&tree->lock); zswap_entry_put(tree, entry); spin_unlock(&tree->lock); @@ -1209,6 +1268,8 @@ static int __init zswap_debugfs_init(void) zswap_debugfs_root, &zswap_pool_total_size); debugfs_create_atomic_t("stored_pages", S_IRUGO, zswap_debugfs_root, &zswap_stored_pages); + debugfs_create_atomic_t("same_filled_pages", 0444, + zswap_debugfs_root, &zswap_same_filled_pages); return 0; } -- 2.7.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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