From 0f8975ec4db2c8b5bd111b211292ca9be0feb6b8 Mon Sep 17 00:00:00 2001 From: Pavel Emelyanov Date: Wed, 3 Jul 2013 15:01:20 -0700 Subject: mm: soft-dirty bits for user memory changes tracking The soft-dirty is a bit on a PTE which helps to track which pages a task writes to. In order to do this tracking one should 1. Clear soft-dirty bits from PTEs ("echo 4 > /proc/PID/clear_refs) 2. Wait some time. 3. Read soft-dirty bits (55'th in /proc/PID/pagemap2 entries) To do this tracking, the writable bit is cleared from PTEs when the soft-dirty bit is. Thus, after this, when the task tries to modify a page at some virtual address the #PF occurs and the kernel sets the soft-dirty bit on the respective PTE. Note, that although all the task's address space is marked as r/o after the soft-dirty bits clear, the #PF-s that occur after that are processed fast. This is so, since the pages are still mapped to physical memory, and thus all the kernel does is finds this fact out and puts back writable, dirty and soft-dirty bits on the PTE. Another thing to note, is that when mremap moves PTEs they are marked with soft-dirty as well, since from the user perspective mremap modifies the virtual memory at mremap's new address. Signed-off-by: Pavel Emelyanov Cc: Matt Mackall Cc: Xiao Guangrong Cc: Glauber Costa Cc: Marcelo Tosatti Cc: KOSAKI Motohiro Cc: Stephen Rothwell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/Kconfig | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'mm/Kconfig') diff --git a/mm/Kconfig b/mm/Kconfig index f5e698e30d4a..7e28ecfa8aa4 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -477,3 +477,15 @@ config FRONTSWAP and swap data is stored as normal on the matching swap device. If unsure, say Y to enable frontswap. + +config MEM_SOFT_DIRTY + bool "Track memory changes" + depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY + select PROC_PAGE_MONITOR + help + This option enables memory changes tracking by introducing a + soft-dirty bit on pte-s. This bit it set when someone writes + into a page just as regular dirty bit, but unlike the latter + it can be cleared by hands. + + See Documentation/vm/soft-dirty.txt for more details. -- cgit v1.2.3 From 4e2e2770b1529edc5849c86b29a6febe27e2f083 Mon Sep 17 00:00:00 2001 From: Seth Jennings Date: Wed, 10 Jul 2013 16:04:55 -0700 Subject: zbud: add to mm/ zbud is an special purpose allocator for storing compressed pages. It is designed to store up to two compressed pages per physical page. While this design limits storage density, it has simple and deterministic reclaim properties that make it preferable to a higher density approach when reclaim will be used. zbud works by storing compressed pages, or "zpages", together in pairs in a single memory page called a "zbud page". The first buddy is "left justifed" at the beginning of the zbud page, and the last buddy is "right justified" at the end of the zbud page. The benefit is that if either buddy is freed, the freed buddy space, coalesced with whatever slack space that existed between the buddies, results in the largest possible free region within the zbud page. zbud also provides an attractive lower bound on density. The ratio of zpages to zbud pages can not be less than 1. This ensures that zbud can never "do harm" by using more pages to store zpages than the uncompressed zpages would have used on their own. This implementation is a rewrite of the zbud allocator internally used by zcache in the driver/staging tree. The rewrite was necessary to remove some of the zcache specific elements that were ingrained throughout and provide a generic allocation interface that can later be used by zsmalloc and others. This patch adds zbud to mm/ for later use by zswap. Signed-off-by: Seth Jennings Acked-by: Rik van Riel Cc: Greg Kroah-Hartman Cc: Nitin Gupta Cc: Minchan Kim Cc: Konrad Rzeszutek Wilk Cc: Dan Magenheimer Cc: Robert Jennings Cc: Jenifer Hopper Cc: Mel Gorman Cc: Johannes Weiner Cc: Larry Woodman Cc: Benjamin Herrenschmidt Cc: Dave Hansen Cc: Joe Perches Cc: Joonsoo Kim Cc: Cody P Schafer Cc: Hugh Dickens Cc: Paul Mackerras Cc: Bob Liu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/zbud.h | 22 +++ mm/Kconfig | 10 + mm/Makefile | 1 + mm/zbud.c | 527 +++++++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 560 insertions(+) create mode 100644 include/linux/zbud.h create mode 100644 mm/zbud.c (limited to 'mm/Kconfig') diff --git a/include/linux/zbud.h b/include/linux/zbud.h new file mode 100644 index 000000000000..2571a5cfa5fc --- /dev/null +++ b/include/linux/zbud.h @@ -0,0 +1,22 @@ +#ifndef _ZBUD_H_ +#define _ZBUD_H_ + +#include + +struct zbud_pool; + +struct zbud_ops { + int (*evict)(struct zbud_pool *pool, unsigned long handle); +}; + +struct zbud_pool *zbud_create_pool(gfp_t gfp, struct zbud_ops *ops); +void zbud_destroy_pool(struct zbud_pool *pool); +int zbud_alloc(struct zbud_pool *pool, int size, gfp_t gfp, + unsigned long *handle); +void zbud_free(struct zbud_pool *pool, unsigned long handle); +int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries); +void *zbud_map(struct zbud_pool *pool, unsigned long handle); +void zbud_unmap(struct zbud_pool *pool, unsigned long handle); +u64 zbud_get_pool_size(struct zbud_pool *pool); + +#endif /* _ZBUD_H_ */ diff --git a/mm/Kconfig b/mm/Kconfig index 7e28ecfa8aa4..45503ed5f3aa 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -478,6 +478,16 @@ config FRONTSWAP If unsure, say Y to enable frontswap. +config ZBUD + tristate + default n + help + A special purpose allocator for storing compressed pages. + It is designed to store up to two compressed pages per physical + page. While this design limits storage density, it has simple and + deterministic reclaim properties that make it preferable to a higher + density approach when reclaim will be used. + config MEM_SOFT_DIRTY bool "Track memory changes" depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY diff --git a/mm/Makefile b/mm/Makefile index 72c5acb9345f..95f0197ce3d3 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -58,3 +58,4 @@ obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o obj-$(CONFIG_CLEANCACHE) += cleancache.o obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o +obj-$(CONFIG_ZBUD) += zbud.o diff --git a/mm/zbud.c b/mm/zbud.c new file mode 100644 index 000000000000..9bb4710e3589 --- /dev/null +++ b/mm/zbud.c @@ -0,0 +1,527 @@ +/* + * zbud.c + * + * Copyright (C) 2013, Seth Jennings, IBM + * + * Concepts based on zcache internal zbud allocator by Dan Magenheimer. + * + * zbud is an special purpose allocator for storing compressed pages. Contrary + * to what its name may suggest, zbud is not a buddy allocator, but rather an + * allocator that "buddies" two compressed pages together in a single memory + * page. + * + * While this design limits storage density, it has simple and deterministic + * reclaim properties that make it preferable to a higher density approach when + * reclaim will be used. + * + * zbud works by storing compressed pages, or "zpages", together in pairs in a + * single memory page called a "zbud page". The first buddy is "left + * justifed" at the beginning of the zbud page, and the last buddy is "right + * justified" at the end of the zbud page. The benefit is that if either + * buddy is freed, the freed buddy space, coalesced with whatever slack space + * that existed between the buddies, results in the largest possible free region + * within the zbud page. + * + * zbud also provides an attractive lower bound on density. The ratio of zpages + * to zbud pages can not be less than 1. This ensures that zbud can never "do + * harm" by using more pages to store zpages than the uncompressed zpages would + * have used on their own. + * + * zbud pages are divided into "chunks". The size of the chunks is fixed at + * compile time and determined by NCHUNKS_ORDER below. Dividing zbud pages + * into chunks allows organizing unbuddied zbud pages into a manageable number + * of unbuddied lists according to the number of free chunks available in the + * zbud page. + * + * The zbud API differs from that of conventional allocators in that the + * allocation function, zbud_alloc(), returns an opaque handle to the user, + * not a dereferenceable pointer. The user must map the handle using + * zbud_map() in order to get a usable pointer by which to access the + * allocation data and unmap the handle with zbud_unmap() when operations + * on the allocation data are complete. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include +#include +#include +#include + +/***************** + * Structures +*****************/ +/* + * NCHUNKS_ORDER determines the internal allocation granularity, effectively + * adjusting internal fragmentation. It also determines the number of + * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the + * allocation granularity will be in chunks of size PAGE_SIZE/64, and there + * will be 64 freelists per pool. + */ +#define NCHUNKS_ORDER 6 + +#define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER) +#define CHUNK_SIZE (1 << CHUNK_SHIFT) +#define NCHUNKS (PAGE_SIZE >> CHUNK_SHIFT) +#define ZHDR_SIZE_ALIGNED CHUNK_SIZE + +/** + * struct zbud_pool - stores metadata for each zbud pool + * @lock: protects all pool fields and first|last_chunk fields of any + * zbud page in the pool + * @unbuddied: array of lists tracking zbud pages that only contain one buddy; + * the lists each zbud page is added to depends on the size of + * its free region. + * @buddied: list tracking the zbud pages that contain two buddies; + * these zbud pages are full + * @lru: list tracking the zbud pages in LRU order by most recently + * added buddy. + * @pages_nr: number of zbud pages in the pool. + * @ops: pointer to a structure of user defined operations specified at + * pool creation time. + * + * This structure is allocated at pool creation time and maintains metadata + * pertaining to a particular zbud pool. + */ +struct zbud_pool { + spinlock_t lock; + struct list_head unbuddied[NCHUNKS]; + struct list_head buddied; + struct list_head lru; + u64 pages_nr; + struct zbud_ops *ops; +}; + +/* + * struct zbud_header - zbud page metadata occupying the first chunk of each + * zbud page. + * @buddy: links the zbud page into the unbuddied/buddied lists in the pool + * @lru: links the zbud page into the lru list in the pool + * @first_chunks: the size of the first buddy in chunks, 0 if free + * @last_chunks: the size of the last buddy in chunks, 0 if free + */ +struct zbud_header { + struct list_head buddy; + struct list_head lru; + unsigned int first_chunks; + unsigned int last_chunks; + bool under_reclaim; +}; + +/***************** + * Helpers +*****************/ +/* Just to make the code easier to read */ +enum buddy { + FIRST, + LAST +}; + +/* Converts an allocation size in bytes to size in zbud chunks */ +static int size_to_chunks(int size) +{ + return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT; +} + +#define for_each_unbuddied_list(_iter, _begin) \ + for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++) + +/* Initializes the zbud header of a newly allocated zbud page */ +static struct zbud_header *init_zbud_page(struct page *page) +{ + struct zbud_header *zhdr = page_address(page); + zhdr->first_chunks = 0; + zhdr->last_chunks = 0; + INIT_LIST_HEAD(&zhdr->buddy); + INIT_LIST_HEAD(&zhdr->lru); + zhdr->under_reclaim = 0; + return zhdr; +} + +/* Resets the struct page fields and frees the page */ +static void free_zbud_page(struct zbud_header *zhdr) +{ + __free_page(virt_to_page(zhdr)); +} + +/* + * Encodes the handle of a particular buddy within a zbud page + * Pool lock should be held as this function accesses first|last_chunks + */ +static unsigned long encode_handle(struct zbud_header *zhdr, enum buddy bud) +{ + unsigned long handle; + + /* + * For now, the encoded handle is actually just the pointer to the data + * but this might not always be the case. A little information hiding. + * Add CHUNK_SIZE to the handle if it is the first allocation to jump + * over the zbud header in the first chunk. + */ + handle = (unsigned long)zhdr; + if (bud == FIRST) + /* skip over zbud header */ + handle += ZHDR_SIZE_ALIGNED; + else /* bud == LAST */ + handle += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT); + return handle; +} + +/* Returns the zbud page where a given handle is stored */ +static struct zbud_header *handle_to_zbud_header(unsigned long handle) +{ + return (struct zbud_header *)(handle & PAGE_MASK); +} + +/* Returns the number of free chunks in a zbud page */ +static int num_free_chunks(struct zbud_header *zhdr) +{ + /* + * Rather than branch for different situations, just use the fact that + * free buddies have a length of zero to simplify everything. -1 at the + * end for the zbud header. + */ + return NCHUNKS - zhdr->first_chunks - zhdr->last_chunks - 1; +} + +/***************** + * API Functions +*****************/ +/** + * zbud_create_pool() - create a new zbud pool + * @gfp: gfp flags when allocating the zbud pool structure + * @ops: user-defined operations for the zbud pool + * + * Return: pointer to the new zbud pool or NULL if the metadata allocation + * failed. + */ +struct zbud_pool *zbud_create_pool(gfp_t gfp, struct zbud_ops *ops) +{ + struct zbud_pool *pool; + int i; + + pool = kmalloc(sizeof(struct zbud_pool), gfp); + if (!pool) + return NULL; + spin_lock_init(&pool->lock); + for_each_unbuddied_list(i, 0) + INIT_LIST_HEAD(&pool->unbuddied[i]); + INIT_LIST_HEAD(&pool->buddied); + INIT_LIST_HEAD(&pool->lru); + pool->pages_nr = 0; + pool->ops = ops; + return pool; +} + +/** + * zbud_destroy_pool() - destroys an existing zbud pool + * @pool: the zbud pool to be destroyed + * + * The pool should be emptied before this function is called. + */ +void zbud_destroy_pool(struct zbud_pool *pool) +{ + kfree(pool); +} + +/** + * zbud_alloc() - allocates a region of a given size + * @pool: zbud pool from which to allocate + * @size: size in bytes of the desired allocation + * @gfp: gfp flags used if the pool needs to grow + * @handle: handle of the new allocation + * + * This function will attempt to find a free region in the pool large enough to + * satisfy the allocation request. A search of the unbuddied lists is + * performed first. If no suitable free region is found, then a new page is + * allocated and added to the pool to satisfy the request. + * + * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used + * as zbud pool pages. + * + * Return: 0 if success and handle is set, otherwise -EINVAL is the size or + * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate + * a new page. + */ +int zbud_alloc(struct zbud_pool *pool, int size, gfp_t gfp, + unsigned long *handle) +{ + int chunks, i, freechunks; + struct zbud_header *zhdr = NULL; + enum buddy bud; + struct page *page; + + if (size <= 0 || gfp & __GFP_HIGHMEM) + return -EINVAL; + if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED) + return -ENOSPC; + chunks = size_to_chunks(size); + spin_lock(&pool->lock); + + /* First, try to find an unbuddied zbud page. */ + zhdr = NULL; + for_each_unbuddied_list(i, chunks) { + if (!list_empty(&pool->unbuddied[i])) { + zhdr = list_first_entry(&pool->unbuddied[i], + struct zbud_header, buddy); + list_del(&zhdr->buddy); + if (zhdr->first_chunks == 0) + bud = FIRST; + else + bud = LAST; + goto found; + } + } + + /* Couldn't find unbuddied zbud page, create new one */ + spin_unlock(&pool->lock); + page = alloc_page(gfp); + if (!page) + return -ENOMEM; + spin_lock(&pool->lock); + pool->pages_nr++; + zhdr = init_zbud_page(page); + bud = FIRST; + +found: + if (bud == FIRST) + zhdr->first_chunks = chunks; + else + zhdr->last_chunks = chunks; + + if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0) { + /* Add to unbuddied list */ + freechunks = num_free_chunks(zhdr); + list_add(&zhdr->buddy, &pool->unbuddied[freechunks]); + } else { + /* Add to buddied list */ + list_add(&zhdr->buddy, &pool->buddied); + } + + /* Add/move zbud page to beginning of LRU */ + if (!list_empty(&zhdr->lru)) + list_del(&zhdr->lru); + list_add(&zhdr->lru, &pool->lru); + + *handle = encode_handle(zhdr, bud); + spin_unlock(&pool->lock); + + return 0; +} + +/** + * zbud_free() - frees the allocation associated with the given handle + * @pool: pool in which the allocation resided + * @handle: handle associated with the allocation returned by zbud_alloc() + * + * In the case that the zbud page in which the allocation resides is under + * reclaim, as indicated by the PG_reclaim flag being set, this function + * only sets the first|last_chunks to 0. The page is actually freed + * once both buddies are evicted (see zbud_reclaim_page() below). + */ +void zbud_free(struct zbud_pool *pool, unsigned long handle) +{ + struct zbud_header *zhdr; + int freechunks; + + spin_lock(&pool->lock); + zhdr = handle_to_zbud_header(handle); + + /* If first buddy, handle will be page aligned */ + if ((handle - ZHDR_SIZE_ALIGNED) & ~PAGE_MASK) + zhdr->last_chunks = 0; + else + zhdr->first_chunks = 0; + + if (zhdr->under_reclaim) { + /* zbud page is under reclaim, reclaim will free */ + spin_unlock(&pool->lock); + return; + } + + /* Remove from existing buddy list */ + list_del(&zhdr->buddy); + + if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) { + /* zbud page is empty, free */ + list_del(&zhdr->lru); + free_zbud_page(zhdr); + pool->pages_nr--; + } else { + /* Add to unbuddied list */ + freechunks = num_free_chunks(zhdr); + list_add(&zhdr->buddy, &pool->unbuddied[freechunks]); + } + + spin_unlock(&pool->lock); +} + +#define list_tail_entry(ptr, type, member) \ + list_entry((ptr)->prev, type, member) + +/** + * zbud_reclaim_page() - evicts allocations from a pool page and frees it + * @pool: pool from which a page will attempt to be evicted + * @retires: number of pages on the LRU list for which eviction will + * be attempted before failing + * + * zbud reclaim is different from normal system reclaim in that the reclaim is + * done from the bottom, up. This is because only the bottom layer, zbud, has + * information on how the allocations are organized within each zbud page. This + * has the potential to create interesting locking situations between zbud and + * the user, however. + * + * To avoid these, this is how zbud_reclaim_page() should be called: + + * The user detects a page should be reclaimed and calls zbud_reclaim_page(). + * zbud_reclaim_page() will remove a zbud page from the pool LRU list and call + * the user-defined eviction handler with the pool and handle as arguments. + * + * If the handle can not be evicted, the eviction handler should return + * non-zero. zbud_reclaim_page() will add the zbud page back to the + * appropriate list and try the next zbud page on the LRU up to + * a user defined number of retries. + * + * If the handle is successfully evicted, the eviction handler should + * return 0 _and_ should have called zbud_free() on the handle. zbud_free() + * contains logic to delay freeing the page if the page is under reclaim, + * as indicated by the setting of the PG_reclaim flag on the underlying page. + * + * If all buddies in the zbud page are successfully evicted, then the + * zbud page can be freed. + * + * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are + * no pages to evict or an eviction handler is not registered, -EAGAIN if + * the retry limit was hit. + */ +int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries) +{ + int i, ret, freechunks; + struct zbud_header *zhdr; + unsigned long first_handle = 0, last_handle = 0; + + spin_lock(&pool->lock); + if (!pool->ops || !pool->ops->evict || list_empty(&pool->lru) || + retries == 0) { + spin_unlock(&pool->lock); + return -EINVAL; + } + for (i = 0; i < retries; i++) { + zhdr = list_tail_entry(&pool->lru, struct zbud_header, lru); + list_del(&zhdr->lru); + list_del(&zhdr->buddy); + /* Protect zbud page against free */ + zhdr->under_reclaim = true; + /* + * We need encode the handles before unlocking, since we can + * race with free that will set (first|last)_chunks to 0 + */ + first_handle = 0; + last_handle = 0; + if (zhdr->first_chunks) + first_handle = encode_handle(zhdr, FIRST); + if (zhdr->last_chunks) + last_handle = encode_handle(zhdr, LAST); + spin_unlock(&pool->lock); + + /* Issue the eviction callback(s) */ + if (first_handle) { + ret = pool->ops->evict(pool, first_handle); + if (ret) + goto next; + } + if (last_handle) { + ret = pool->ops->evict(pool, last_handle); + if (ret) + goto next; + } +next: + spin_lock(&pool->lock); + zhdr->under_reclaim = false; + if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) { + /* + * Both buddies are now free, free the zbud page and + * return success. + */ + free_zbud_page(zhdr); + pool->pages_nr--; + spin_unlock(&pool->lock); + return 0; + } else if (zhdr->first_chunks == 0 || + zhdr->last_chunks == 0) { + /* add to unbuddied list */ + freechunks = num_free_chunks(zhdr); + list_add(&zhdr->buddy, &pool->unbuddied[freechunks]); + } else { + /* add to buddied list */ + list_add(&zhdr->buddy, &pool->buddied); + } + + /* add to beginning of LRU */ + list_add(&zhdr->lru, &pool->lru); + } + spin_unlock(&pool->lock); + return -EAGAIN; +} + +/** + * zbud_map() - maps the allocation associated with the given handle + * @pool: pool in which the allocation resides + * @handle: handle associated with the allocation to be mapped + * + * While trivial for zbud, the mapping functions for others allocators + * implementing this allocation API could have more complex information encoded + * in the handle and could create temporary mappings to make the data + * accessible to the user. + * + * Returns: a pointer to the mapped allocation + */ +void *zbud_map(struct zbud_pool *pool, unsigned long handle) +{ + return (void *)(handle); +} + +/** + * zbud_unmap() - maps the allocation associated with the given handle + * @pool: pool in which the allocation resides + * @handle: handle associated with the allocation to be unmapped + */ +void zbud_unmap(struct zbud_pool *pool, unsigned long handle) +{ +} + +/** + * zbud_get_pool_size() - gets the zbud pool size in pages + * @pool: pool whose size is being queried + * + * Returns: size in pages of the given pool. The pool lock need not be + * taken to access pages_nr. + */ +u64 zbud_get_pool_size(struct zbud_pool *pool) +{ + return pool->pages_nr; +} + +static int __init init_zbud(void) +{ + /* Make sure the zbud header will fit in one chunk */ + BUILD_BUG_ON(sizeof(struct zbud_header) > ZHDR_SIZE_ALIGNED); + pr_info("loaded\n"); + return 0; +} + +static void __exit exit_zbud(void) +{ + pr_info("unloaded\n"); +} + +module_init(init_zbud); +module_exit(exit_zbud); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Seth Jennings "); +MODULE_DESCRIPTION("Buddy Allocator for Compressed Pages"); -- cgit v1.2.3 From 2b2811178e85553405b86e3fe78357b9b95889ce Mon Sep 17 00:00:00 2001 From: Seth Jennings Date: Wed, 10 Jul 2013 16:05:03 -0700 Subject: zswap: add to mm/ zswap is a thin backend for frontswap that takes pages that are in the process of being swapped out and attempts to compress them and store them in a RAM-based memory pool. This can result in a significant I/O reduction on the swap device and, in the case where decompressing from RAM is faster than reading from the swap device, can also improve workload performance. It also has support for evicting swap pages that are currently compressed in zswap to the swap device on an LRU(ish) basis. This functionality makes zswap a true cache in that, once the cache is full, the oldest pages can be moved out of zswap to the swap device so newer pages can be compressed and stored in zswap. This patch adds the zswap driver to mm/ Signed-off-by: Seth Jennings Acked-by: Rik van Riel Cc: Greg Kroah-Hartman Cc: Nitin Gupta Cc: Minchan Kim Cc: Konrad Rzeszutek Wilk Cc: Dan Magenheimer Cc: Robert Jennings Cc: Jenifer Hopper Cc: Mel Gorman Cc: Johannes Weiner Cc: Larry Woodman Cc: Benjamin Herrenschmidt Cc: Dave Hansen Cc: Joe Perches Cc: Joonsoo Kim Cc: Cody P Schafer Cc: Hugh Dickens Cc: Paul Mackerras Cc: Fengguang Wu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/Kconfig | 20 ++ mm/Makefile | 1 + mm/zswap.c | 943 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 964 insertions(+) create mode 100644 mm/zswap.c (limited to 'mm/Kconfig') diff --git a/mm/Kconfig b/mm/Kconfig index 45503ed5f3aa..8028dcc6615c 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -488,6 +488,26 @@ config ZBUD deterministic reclaim properties that make it preferable to a higher density approach when reclaim will be used. +config ZSWAP + bool "Compressed cache for swap pages (EXPERIMENTAL)" + depends on FRONTSWAP && CRYPTO=y + select CRYPTO_LZO + select ZBUD + default n + help + A lightweight compressed cache for swap pages. It takes + pages that are in the process of being swapped out and attempts to + compress them into a dynamically allocated RAM-based memory pool. + This can result in a significant I/O reduction on swap device and, + in the case where decompressing from RAM is faster that swap device + reads, can also improve workload performance. + + This is marked experimental because it is a new feature (as of + v3.11) that interacts heavily with memory reclaim. While these + interactions don't cause any known issues on simple memory setups, + they have not be fully explored on the large set of potential + configurations and workloads that exist. + config MEM_SOFT_DIRTY bool "Track memory changes" depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY diff --git a/mm/Makefile b/mm/Makefile index 95f0197ce3d3..f00803386a67 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -32,6 +32,7 @@ obj-$(CONFIG_HAVE_MEMBLOCK) += memblock.o obj-$(CONFIG_BOUNCE) += bounce.o obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o obj-$(CONFIG_FRONTSWAP) += frontswap.o +obj-$(CONFIG_ZSWAP) += zswap.o obj-$(CONFIG_HAS_DMA) += dmapool.o obj-$(CONFIG_HUGETLBFS) += hugetlb.o obj-$(CONFIG_NUMA) += mempolicy.o diff --git a/mm/zswap.c b/mm/zswap.c new file mode 100644 index 000000000000..deda2b671e12 --- /dev/null +++ b/mm/zswap.c @@ -0,0 +1,943 @@ +/* + * zswap.c - zswap driver file + * + * zswap is a backend for frontswap that takes pages that are in the process + * of being swapped out and attempts to compress and store them in a + * RAM-based memory pool. This can result in a significant I/O reduction on + * the swap device and, in the case where decompressing from RAM is faster + * than reading from the swap device, can also improve workload performance. + * + * Copyright (C) 2012 Seth Jennings + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. +*/ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include + +/********************************* +* statistics +**********************************/ +/* Number of memory pages used by the compressed pool */ +static u64 zswap_pool_pages; +/* The number of compressed pages currently stored in zswap */ +static atomic_t zswap_stored_pages = ATOMIC_INIT(0); + +/* + * The statistics below are not protected from concurrent access for + * performance reasons so they may not be a 100% accurate. However, + * they do provide useful information on roughly how many times a + * certain event is occurring. +*/ + +/* Pool limit was hit (see zswap_max_pool_percent) */ +static u64 zswap_pool_limit_hit; +/* Pages written back when pool limit was reached */ +static u64 zswap_written_back_pages; +/* Store failed due to a reclaim failure after pool limit was reached */ +static u64 zswap_reject_reclaim_fail; +/* Compressed page was too big for the allocator to (optimally) store */ +static u64 zswap_reject_compress_poor; +/* Store failed because underlying allocator could not get memory */ +static u64 zswap_reject_alloc_fail; +/* Store failed because the entry metadata could not be allocated (rare) */ +static u64 zswap_reject_kmemcache_fail; +/* Duplicate store was encountered (rare) */ +static u64 zswap_duplicate_entry; + +/********************************* +* tunables +**********************************/ +/* Enable/disable zswap (disabled by default, fixed at boot for now) */ +static bool zswap_enabled __read_mostly; +module_param_named(enabled, zswap_enabled, bool, 0); + +/* Compressor to be used by zswap (fixed at boot for now) */ +#define ZSWAP_COMPRESSOR_DEFAULT "lzo" +static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT; +module_param_named(compressor, zswap_compressor, charp, 0); + +/* The maximum percentage of memory that the compressed pool can occupy */ +static unsigned int zswap_max_pool_percent = 20; +module_param_named(max_pool_percent, + zswap_max_pool_percent, uint, 0644); + +/********************************* +* compression functions +**********************************/ +/* per-cpu compression transforms */ +static struct crypto_comp * __percpu *zswap_comp_pcpu_tfms; + +enum comp_op { + ZSWAP_COMPOP_COMPRESS, + ZSWAP_COMPOP_DECOMPRESS +}; + +static int zswap_comp_op(enum comp_op op, const u8 *src, unsigned int slen, + u8 *dst, unsigned int *dlen) +{ + struct crypto_comp *tfm; + int ret; + + tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, get_cpu()); + switch (op) { + case ZSWAP_COMPOP_COMPRESS: + ret = crypto_comp_compress(tfm, src, slen, dst, dlen); + break; + case ZSWAP_COMPOP_DECOMPRESS: + ret = crypto_comp_decompress(tfm, src, slen, dst, dlen); + break; + default: + ret = -EINVAL; + } + + put_cpu(); + return ret; +} + +static int __init zswap_comp_init(void) +{ + if (!crypto_has_comp(zswap_compressor, 0, 0)) { + pr_info("%s compressor not available\n", zswap_compressor); + /* fall back to default compressor */ + zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT; + if (!crypto_has_comp(zswap_compressor, 0, 0)) + /* can't even load the default compressor */ + return -ENODEV; + } + pr_info("using %s compressor\n", zswap_compressor); + + /* alloc percpu transforms */ + zswap_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *); + if (!zswap_comp_pcpu_tfms) + return -ENOMEM; + return 0; +} + +static void zswap_comp_exit(void) +{ + /* free percpu transforms */ + if (zswap_comp_pcpu_tfms) + free_percpu(zswap_comp_pcpu_tfms); +} + +/********************************* +* data structures +**********************************/ +/* + * struct zswap_entry + * + * This structure contains the metadata for tracking a single compressed + * page within zswap. + * + * rbnode - links the entry into red-black tree for the appropriate swap type + * refcount - the number of outstanding reference to the entry. This is needed + * to protect against premature freeing of the entry by code + * concurent calls to load, invalidate, and writeback. The lock + * for the zswap_tree structure that contains the entry must + * be held while changing the refcount. Since the lock must + * be held, there is no reason to also make refcount atomic. + * offset - the swap offset for the entry. Index into the red-black tree. + * handle - zsmalloc allocation handle that stores the compressed page data + * length - the length in bytes of the compressed page data. Needed during + * decompression + */ +struct zswap_entry { + struct rb_node rbnode; + pgoff_t offset; + int refcount; + unsigned int length; + unsigned long handle; +}; + +struct zswap_header { + swp_entry_t swpentry; +}; + +/* + * The tree lock in the zswap_tree struct protects a few things: + * - the rbtree + * - the refcount field of each entry in the tree + */ +struct zswap_tree { + struct rb_root rbroot; + spinlock_t lock; + struct zbud_pool *pool; +}; + +static struct zswap_tree *zswap_trees[MAX_SWAPFILES]; + +/********************************* +* zswap entry functions +**********************************/ +static struct kmem_cache *zswap_entry_cache; + +static int zswap_entry_cache_create(void) +{ + zswap_entry_cache = KMEM_CACHE(zswap_entry, 0); + return (zswap_entry_cache == NULL); +} + +static void zswap_entry_cache_destory(void) +{ + kmem_cache_destroy(zswap_entry_cache); +} + +static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp) +{ + struct zswap_entry *entry; + entry = kmem_cache_alloc(zswap_entry_cache, gfp); + if (!entry) + return NULL; + entry->refcount = 1; + return entry; +} + +static void zswap_entry_cache_free(struct zswap_entry *entry) +{ + kmem_cache_free(zswap_entry_cache, entry); +} + +/* caller must hold the tree lock */ +static void zswap_entry_get(struct zswap_entry *entry) +{ + entry->refcount++; +} + +/* caller must hold the tree lock */ +static int zswap_entry_put(struct zswap_entry *entry) +{ + entry->refcount--; + return entry->refcount; +} + +/********************************* +* rbtree functions +**********************************/ +static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset) +{ + struct rb_node *node = root->rb_node; + struct zswap_entry *entry; + + while (node) { + entry = rb_entry(node, struct zswap_entry, rbnode); + if (entry->offset > offset) + node = node->rb_left; + else if (entry->offset < offset) + node = node->rb_right; + else + return entry; + } + return NULL; +} + +/* + * In the case that a entry with the same offset is found, a pointer to + * the existing entry is stored in dupentry and the function returns -EEXIST + */ +static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry, + struct zswap_entry **dupentry) +{ + struct rb_node **link = &root->rb_node, *parent = NULL; + struct zswap_entry *myentry; + + while (*link) { + parent = *link; + myentry = rb_entry(parent, struct zswap_entry, rbnode); + if (myentry->offset > entry->offset) + link = &(*link)->rb_left; + else if (myentry->offset < entry->offset) + link = &(*link)->rb_right; + else { + *dupentry = myentry; + return -EEXIST; + } + } + rb_link_node(&entry->rbnode, parent, link); + rb_insert_color(&entry->rbnode, root); + return 0; +} + +/********************************* +* per-cpu code +**********************************/ +static DEFINE_PER_CPU(u8 *, zswap_dstmem); + +static int __zswap_cpu_notifier(unsigned long action, unsigned long cpu) +{ + struct crypto_comp *tfm; + u8 *dst; + + switch (action) { + case CPU_UP_PREPARE: + tfm = crypto_alloc_comp(zswap_compressor, 0, 0); + if (IS_ERR(tfm)) { + pr_err("can't allocate compressor transform\n"); + return NOTIFY_BAD; + } + *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = tfm; + dst = kmalloc(PAGE_SIZE * 2, GFP_KERNEL); + if (!dst) { + pr_err("can't allocate compressor buffer\n"); + crypto_free_comp(tfm); + *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL; + return NOTIFY_BAD; + } + per_cpu(zswap_dstmem, cpu) = dst; + break; + case CPU_DEAD: + case CPU_UP_CANCELED: + tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu); + if (tfm) { + crypto_free_comp(tfm); + *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL; + } + dst = per_cpu(zswap_dstmem, cpu); + kfree(dst); + per_cpu(zswap_dstmem, cpu) = NULL; + break; + default: + break; + } + return NOTIFY_OK; +} + +static int zswap_cpu_notifier(struct notifier_block *nb, + unsigned long action, void *pcpu) +{ + unsigned long cpu = (unsigned long)pcpu; + return __zswap_cpu_notifier(action, cpu); +} + +static struct notifier_block zswap_cpu_notifier_block = { + .notifier_call = zswap_cpu_notifier +}; + +static int zswap_cpu_init(void) +{ + unsigned long cpu; + + get_online_cpus(); + for_each_online_cpu(cpu) + if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK) + goto cleanup; + register_cpu_notifier(&zswap_cpu_notifier_block); + put_online_cpus(); + return 0; + +cleanup: + for_each_online_cpu(cpu) + __zswap_cpu_notifier(CPU_UP_CANCELED, cpu); + put_online_cpus(); + return -ENOMEM; +} + +/********************************* +* helpers +**********************************/ +static bool zswap_is_full(void) +{ + return (totalram_pages * zswap_max_pool_percent / 100 < + zswap_pool_pages); +} + +/* + * Carries out the common pattern of freeing and entry's zsmalloc allocation, + * freeing the entry itself, and decrementing the number of stored pages. + */ +static void zswap_free_entry(struct zswap_tree *tree, struct zswap_entry *entry) +{ + zbud_free(tree->pool, entry->handle); + zswap_entry_cache_free(entry); + atomic_dec(&zswap_stored_pages); + zswap_pool_pages = zbud_get_pool_size(tree->pool); +} + +/********************************* +* writeback code +**********************************/ +/* return enum for zswap_get_swap_cache_page */ +enum zswap_get_swap_ret { + ZSWAP_SWAPCACHE_NEW, + ZSWAP_SWAPCACHE_EXIST, + ZSWAP_SWAPCACHE_NOMEM +}; + +/* + * zswap_get_swap_cache_page + * + * This is an adaption of read_swap_cache_async() + * + * This function tries to find a page with the given swap entry + * in the swapper_space address space (the swap cache). If the page + * is found, it is returned in retpage. Otherwise, a page is allocated, + * added to the swap cache, and returned in retpage. + * + * If success, the swap cache page is returned in retpage + * Returns 0 if page was already in the swap cache, page is not locked + * Returns 1 if the new page needs to be populated, page is locked + * Returns <0 on error + */ +static int zswap_get_swap_cache_page(swp_entry_t entry, + struct page **retpage) +{ + struct page *found_page, *new_page = NULL; + struct address_space *swapper_space = &swapper_spaces[swp_type(entry)]; + int err; + + *retpage = NULL; + do { + /* + * First check the swap cache. Since this is normally + * called after lookup_swap_cache() failed, re-calling + * that would confuse statistics. + */ + found_page = find_get_page(swapper_space, entry.val); + if (found_page) + break; + + /* + * Get a new page to read into from swap. + */ + if (!new_page) { + new_page = alloc_page(GFP_KERNEL); + if (!new_page) + break; /* Out of memory */ + } + + /* + * call radix_tree_preload() while we can wait. + */ + err = radix_tree_preload(GFP_KERNEL); + if (err) + break; + + /* + * Swap entry may have been freed since our caller observed it. + */ + err = swapcache_prepare(entry); + if (err == -EEXIST) { /* seems racy */ + radix_tree_preload_end(); + continue; + } + if (err) { /* swp entry is obsolete ? */ + radix_tree_preload_end(); + break; + } + + /* May fail (-ENOMEM) if radix-tree node allocation failed. */ + __set_page_locked(new_page); + SetPageSwapBacked(new_page); + err = __add_to_swap_cache(new_page, entry); + if (likely(!err)) { + radix_tree_preload_end(); + lru_cache_add_anon(new_page); + *retpage = new_page; + return ZSWAP_SWAPCACHE_NEW; + } + radix_tree_preload_end(); + ClearPageSwapBacked(new_page); + __clear_page_locked(new_page); + /* + * add_to_swap_cache() doesn't return -EEXIST, so we can safely + * clear SWAP_HAS_CACHE flag. + */ + swapcache_free(entry, NULL); + } while (err != -ENOMEM); + + if (new_page) + page_cache_release(new_page); + if (!found_page) + return ZSWAP_SWAPCACHE_NOMEM; + *retpage = found_page; + return ZSWAP_SWAPCACHE_EXIST; +} + +/* + * Attempts to free an entry by adding a page to the swap cache, + * decompressing the entry data into the page, and issuing a + * bio write to write the page back to the swap device. + * + * This can be thought of as a "resumed writeback" of the page + * to the swap device. We are basically resuming the same swap + * writeback path that was intercepted with the frontswap_store() + * in the first place. After the page has been decompressed into + * the swap cache, the compressed version stored by zswap can be + * freed. + */ +static int zswap_writeback_entry(struct zbud_pool *pool, unsigned long handle) +{ + struct zswap_header *zhdr; + swp_entry_t swpentry; + struct zswap_tree *tree; + pgoff_t offset; + struct zswap_entry *entry; + struct page *page; + u8 *src, *dst; + unsigned int dlen; + int ret, refcount; + struct writeback_control wbc = { + .sync_mode = WB_SYNC_NONE, + }; + + /* extract swpentry from data */ + zhdr = zbud_map(pool, handle); + swpentry = zhdr->swpentry; /* here */ + zbud_unmap(pool, handle); + tree = zswap_trees[swp_type(swpentry)]; + offset = swp_offset(swpentry); + BUG_ON(pool != tree->pool); + + /* find and ref zswap entry */ + spin_lock(&tree->lock); + entry = zswap_rb_search(&tree->rbroot, offset); + if (!entry) { + /* entry was invalidated */ + spin_unlock(&tree->lock); + return 0; + } + zswap_entry_get(entry); + spin_unlock(&tree->lock); + BUG_ON(offset != entry->offset); + + /* try to allocate swap cache page */ + switch (zswap_get_swap_cache_page(swpentry, &page)) { + case ZSWAP_SWAPCACHE_NOMEM: /* no memory */ + ret = -ENOMEM; + goto fail; + + case ZSWAP_SWAPCACHE_EXIST: /* page is unlocked */ + /* page is already in the swap cache, ignore for now */ + page_cache_release(page); + ret = -EEXIST; + goto fail; + + case ZSWAP_SWAPCACHE_NEW: /* page is locked */ + /* decompress */ + dlen = PAGE_SIZE; + src = (u8 *)zbud_map(tree->pool, entry->handle) + + sizeof(struct zswap_header); + dst = kmap_atomic(page); + ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, + entry->length, dst, &dlen); + kunmap_atomic(dst); + zbud_unmap(tree->pool, entry->handle); + BUG_ON(ret); + BUG_ON(dlen != PAGE_SIZE); + + /* page is up to date */ + SetPageUptodate(page); + } + + /* start writeback */ + __swap_writepage(page, &wbc, end_swap_bio_write); + page_cache_release(page); + zswap_written_back_pages++; + + spin_lock(&tree->lock); + + /* drop local reference */ + zswap_entry_put(entry); + /* drop the initial reference from entry creation */ + refcount = zswap_entry_put(entry); + + /* + * There are three possible values for refcount here: + * (1) refcount is 1, load is in progress, unlink from rbtree, + * load will free + * (2) refcount is 0, (normal case) entry is valid, + * remove from rbtree and free entry + * (3) refcount is -1, invalidate happened during writeback, + * free entry + */ + if (refcount >= 0) { + /* no invalidate yet, remove from rbtree */ + rb_erase(&entry->rbnode, &tree->rbroot); + } + spin_unlock(&tree->lock); + if (refcount <= 0) { + /* free the entry */ + zswap_free_entry(tree, entry); + return 0; + } + return -EAGAIN; + +fail: + spin_lock(&tree->lock); + zswap_entry_put(entry); + spin_unlock(&tree->lock); + return ret; +} + +/********************************* +* frontswap hooks +**********************************/ +/* attempts to compress and store an single page */ +static int zswap_frontswap_store(unsigned type, pgoff_t offset, + struct page *page) +{ + struct zswap_tree *tree = zswap_trees[type]; + struct zswap_entry *entry, *dupentry; + int ret; + unsigned int dlen = PAGE_SIZE, len; + unsigned long handle; + char *buf; + u8 *src, *dst; + struct zswap_header *zhdr; + + if (!tree) { + ret = -ENODEV; + goto reject; + } + + /* reclaim space if needed */ + if (zswap_is_full()) { + zswap_pool_limit_hit++; + if (zbud_reclaim_page(tree->pool, 8)) { + zswap_reject_reclaim_fail++; + ret = -ENOMEM; + goto reject; + } + } + + /* allocate entry */ + entry = zswap_entry_cache_alloc(GFP_KERNEL); + if (!entry) { + zswap_reject_kmemcache_fail++; + ret = -ENOMEM; + goto reject; + } + + /* compress */ + dst = get_cpu_var(zswap_dstmem); + src = kmap_atomic(page); + ret = zswap_comp_op(ZSWAP_COMPOP_COMPRESS, src, PAGE_SIZE, dst, &dlen); + kunmap_atomic(src); + if (ret) { + ret = -EINVAL; + goto freepage; + } + + /* store */ + len = dlen + sizeof(struct zswap_header); + ret = zbud_alloc(tree->pool, len, __GFP_NORETRY | __GFP_NOWARN, + &handle); + if (ret == -ENOSPC) { + zswap_reject_compress_poor++; + goto freepage; + } + if (ret) { + zswap_reject_alloc_fail++; + goto freepage; + } + zhdr = zbud_map(tree->pool, handle); + zhdr->swpentry = swp_entry(type, offset); + buf = (u8 *)(zhdr + 1); + memcpy(buf, dst, dlen); + zbud_unmap(tree->pool, handle); + put_cpu_var(zswap_dstmem); + + /* populate entry */ + entry->offset = offset; + entry->handle = handle; + entry->length = dlen; + + /* map */ + spin_lock(&tree->lock); + do { + ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry); + if (ret == -EEXIST) { + zswap_duplicate_entry++; + /* remove from rbtree */ + rb_erase(&dupentry->rbnode, &tree->rbroot); + if (!zswap_entry_put(dupentry)) { + /* free */ + zswap_free_entry(tree, dupentry); + } + } + } while (ret == -EEXIST); + spin_unlock(&tree->lock); + + /* update stats */ + atomic_inc(&zswap_stored_pages); + zswap_pool_pages = zbud_get_pool_size(tree->pool); + + return 0; + +freepage: + put_cpu_var(zswap_dstmem); + zswap_entry_cache_free(entry); +reject: + return ret; +} + +/* + * returns 0 if the page was successfully decompressed + * return -1 on entry not found or error +*/ +static int zswap_frontswap_load(unsigned type, pgoff_t offset, + struct page *page) +{ + struct zswap_tree *tree = zswap_trees[type]; + struct zswap_entry *entry; + u8 *src, *dst; + unsigned int dlen; + int refcount, ret; + + /* find */ + spin_lock(&tree->lock); + entry = zswap_rb_search(&tree->rbroot, offset); + if (!entry) { + /* entry was written back */ + spin_unlock(&tree->lock); + return -1; + } + zswap_entry_get(entry); + spin_unlock(&tree->lock); + + /* decompress */ + dlen = PAGE_SIZE; + src = (u8 *)zbud_map(tree->pool, entry->handle) + + sizeof(struct zswap_header); + dst = kmap_atomic(page); + ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length, + dst, &dlen); + kunmap_atomic(dst); + zbud_unmap(tree->pool, entry->handle); + BUG_ON(ret); + + spin_lock(&tree->lock); + refcount = zswap_entry_put(entry); + if (likely(refcount)) { + spin_unlock(&tree->lock); + return 0; + } + spin_unlock(&tree->lock); + + /* + * We don't have to unlink from the rbtree because + * zswap_writeback_entry() or zswap_frontswap_invalidate page() + * has already done this for us if we are the last reference. + */ + /* free */ + + zswap_free_entry(tree, entry); + + return 0; +} + +/* frees an entry in zswap */ +static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset) +{ + struct zswap_tree *tree = zswap_trees[type]; + struct zswap_entry *entry; + int refcount; + + /* find */ + spin_lock(&tree->lock); + entry = zswap_rb_search(&tree->rbroot, offset); + if (!entry) { + /* entry was written back */ + spin_unlock(&tree->lock); + return; + } + + /* remove from rbtree */ + rb_erase(&entry->rbnode, &tree->rbroot); + + /* drop the initial reference from entry creation */ + refcount = zswap_entry_put(entry); + + spin_unlock(&tree->lock); + + if (refcount) { + /* writeback in progress, writeback will free */ + return; + } + + /* free */ + zswap_free_entry(tree, entry); +} + +/* frees all zswap entries for the given swap type */ +static void zswap_frontswap_invalidate_area(unsigned type) +{ + struct zswap_tree *tree = zswap_trees[type]; + struct rb_node *node; + struct zswap_entry *entry; + + if (!tree) + return; + + /* walk the tree and free everything */ + spin_lock(&tree->lock); + /* + * TODO: Even though this code should not be executed because + * the try_to_unuse() in swapoff should have emptied the tree, + * it is very wasteful to rebalance the tree after every + * removal when we are freeing the whole tree. + * + * If post-order traversal code is ever added to the rbtree + * implementation, it should be used here. + */ + while ((node = rb_first(&tree->rbroot))) { + entry = rb_entry(node, struct zswap_entry, rbnode); + rb_erase(&entry->rbnode, &tree->rbroot); + zbud_free(tree->pool, entry->handle); + zswap_entry_cache_free(entry); + atomic_dec(&zswap_stored_pages); + } + tree->rbroot = RB_ROOT; + spin_unlock(&tree->lock); +} + +static struct zbud_ops zswap_zbud_ops = { + .evict = zswap_writeback_entry +}; + +static void zswap_frontswap_init(unsigned type) +{ + struct zswap_tree *tree; + + tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL); + if (!tree) + goto err; + tree->pool = zbud_create_pool(GFP_KERNEL, &zswap_zbud_ops); + if (!tree->pool) + goto freetree; + tree->rbroot = RB_ROOT; + spin_lock_init(&tree->lock); + zswap_trees[type] = tree; + return; + +freetree: + kfree(tree); +err: + pr_err("alloc failed, zswap disabled for swap type %d\n", type); +} + +static struct frontswap_ops zswap_frontswap_ops = { + .store = zswap_frontswap_store, + .load = zswap_frontswap_load, + .invalidate_page = zswap_frontswap_invalidate_page, + .invalidate_area = zswap_frontswap_invalidate_area, + .init = zswap_frontswap_init +}; + +/********************************* +* debugfs functions +**********************************/ +#ifdef CONFIG_DEBUG_FS +#include + +static struct dentry *zswap_debugfs_root; + +static int __init zswap_debugfs_init(void) +{ + if (!debugfs_initialized()) + return -ENODEV; + + zswap_debugfs_root = debugfs_create_dir("zswap", NULL); + if (!zswap_debugfs_root) + return -ENOMEM; + + debugfs_create_u64("pool_limit_hit", S_IRUGO, + zswap_debugfs_root, &zswap_pool_limit_hit); + debugfs_create_u64("reject_reclaim_fail", S_IRUGO, + zswap_debugfs_root, &zswap_reject_reclaim_fail); + debugfs_create_u64("reject_alloc_fail", S_IRUGO, + zswap_debugfs_root, &zswap_reject_alloc_fail); + debugfs_create_u64("reject_kmemcache_fail", S_IRUGO, + zswap_debugfs_root, &zswap_reject_kmemcache_fail); + debugfs_create_u64("reject_compress_poor", S_IRUGO, + zswap_debugfs_root, &zswap_reject_compress_poor); + debugfs_create_u64("written_back_pages", S_IRUGO, + zswap_debugfs_root, &zswap_written_back_pages); + debugfs_create_u64("duplicate_entry", S_IRUGO, + zswap_debugfs_root, &zswap_duplicate_entry); + debugfs_create_u64("pool_pages", S_IRUGO, + zswap_debugfs_root, &zswap_pool_pages); + debugfs_create_atomic_t("stored_pages", S_IRUGO, + zswap_debugfs_root, &zswap_stored_pages); + + return 0; +} + +static void __exit zswap_debugfs_exit(void) +{ + debugfs_remove_recursive(zswap_debugfs_root); +} +#else +static int __init zswap_debugfs_init(void) +{ + return 0; +} + +static void __exit zswap_debugfs_exit(void) { } +#endif + +/********************************* +* module init and exit +**********************************/ +static int __init init_zswap(void) +{ + if (!zswap_enabled) + return 0; + + pr_info("loading zswap\n"); + if (zswap_entry_cache_create()) { + pr_err("entry cache creation failed\n"); + goto error; + } + if (zswap_comp_init()) { + pr_err("compressor initialization failed\n"); + goto compfail; + } + if (zswap_cpu_init()) { + pr_err("per-cpu initialization failed\n"); + goto pcpufail; + } + frontswap_register_ops(&zswap_frontswap_ops); + if (zswap_debugfs_init()) + pr_warn("debugfs initialization failed\n"); + return 0; +pcpufail: + zswap_comp_exit(); +compfail: + zswap_entry_cache_destory(); +error: + return -ENOMEM; +} +/* must be late so crypto has time to come up */ +late_initcall(init_zswap); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Seth Jennings "); +MODULE_DESCRIPTION("Compressed cache for swap pages"); -- cgit v1.2.3