diff options
Diffstat (limited to 'mm/zswap.c')
| -rw-r--r-- | mm/zswap.c | 71 |
1 files changed, 66 insertions, 5 deletions
diff --git a/mm/zswap.c b/mm/zswap.c index d39581a076c3..1133b4ceb72e 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; } |