diff options
Diffstat (limited to 'drivers/staging/zcache/zcache-main.c')
| -rw-r--r-- | drivers/staging/zcache/zcache-main.c | 2003 |
1 files changed, 2003 insertions, 0 deletions
diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c new file mode 100644 index 00000000000..855a5bb56a4 --- /dev/null +++ b/drivers/staging/zcache/zcache-main.c @@ -0,0 +1,2003 @@ +/* + * zcache.c + * + * Copyright (c) 2010,2011, Dan Magenheimer, Oracle Corp. + * Copyright (c) 2010,2011, Nitin Gupta + * + * Zcache provides an in-kernel "host implementation" for transcendent memory + * and, thus indirectly, for cleancache and frontswap. Zcache includes two + * page-accessible memory [1] interfaces, both utilizing lzo1x compression: + * 1) "compression buddies" ("zbud") is used for ephemeral pages + * 2) xvmalloc is used for persistent pages. + * Xvmalloc (based on the TLSF allocator) has very low fragmentation + * so maximizes space efficiency, while zbud allows pairs (and potentially, + * in the future, more than a pair of) compressed pages to be closely linked + * so that reclaiming can be done via the kernel's physical-page-oriented + * "shrinker" interface. + * + * [1] For a definition of page-accessible memory (aka PAM), see: + * http://marc.info/?l=linux-mm&m=127811271605009 + */ + +#include <linux/module.h> +#include <linux/cpu.h> +#include <linux/highmem.h> +#include <linux/list.h> +#include <linux/lzo.h> +#include <linux/slab.h> +#include <linux/spinlock.h> +#include <linux/types.h> +#include <linux/atomic.h> +#include <linux/math64.h> +#include "tmem.h" + +#include "../zram/xvmalloc.h" /* if built in drivers/staging */ + +#if (!defined(CONFIG_CLEANCACHE) && !defined(CONFIG_FRONTSWAP)) +#error "zcache is useless without CONFIG_CLEANCACHE or CONFIG_FRONTSWAP" +#endif +#ifdef CONFIG_CLEANCACHE +#include <linux/cleancache.h> +#endif +#ifdef CONFIG_FRONTSWAP +#include <linux/frontswap.h> +#endif + +#if 0 +/* this is more aggressive but may cause other problems? */ +#define ZCACHE_GFP_MASK (GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN) +#else +#define ZCACHE_GFP_MASK \ + (__GFP_FS | __GFP_NORETRY | __GFP_NOWARN | __GFP_NOMEMALLOC) +#endif + +#define MAX_POOLS_PER_CLIENT 16 + +#define MAX_CLIENTS 16 +#define LOCAL_CLIENT ((uint16_t)-1) + +MODULE_LICENSE("GPL"); + +struct zcache_client { + struct tmem_pool *tmem_pools[MAX_POOLS_PER_CLIENT]; + struct xv_pool *xvpool; + bool allocated; + atomic_t refcount; +}; + +static struct zcache_client zcache_host; +static struct zcache_client zcache_clients[MAX_CLIENTS]; + +static inline uint16_t get_client_id_from_client(struct zcache_client *cli) +{ + BUG_ON(cli == NULL); + if (cli == &zcache_host) + return LOCAL_CLIENT; + return cli - &zcache_clients[0]; +} + +static inline bool is_local_client(struct zcache_client *cli) +{ + return cli == &zcache_host; +} + +/********** + * Compression buddies ("zbud") provides for packing two (or, possibly + * in the future, more) compressed ephemeral pages into a single "raw" + * (physical) page and tracking them with data structures so that + * the raw pages can be easily reclaimed. + * + * A zbud page ("zbpg") is an aligned page containing a list_head, + * a lock, and two "zbud headers". The remainder of the physical + * page is divided up into aligned 64-byte "chunks" which contain + * the compressed data for zero, one, or two zbuds. Each zbpg + * resides on: (1) an "unused list" if it has no zbuds; (2) a + * "buddied" list if it is fully populated with two zbuds; or + * (3) one of PAGE_SIZE/64 "unbuddied" lists indexed by how many chunks + * the one unbuddied zbud uses. The data inside a zbpg cannot be + * read or written unless the zbpg's lock is held. + */ + +#define ZBH_SENTINEL 0x43214321 +#define ZBPG_SENTINEL 0xdeadbeef + +#define ZBUD_MAX_BUDS 2 + +struct zbud_hdr { + uint16_t client_id; + uint16_t pool_id; + struct tmem_oid oid; + uint32_t index; + uint16_t size; /* compressed size in bytes, zero means unused */ + DECL_SENTINEL +}; + +struct zbud_page { + struct list_head bud_list; + spinlock_t lock; + struct zbud_hdr buddy[ZBUD_MAX_BUDS]; + DECL_SENTINEL + /* followed by NUM_CHUNK aligned CHUNK_SIZE-byte chunks */ +}; + +#define CHUNK_SHIFT 6 +#define CHUNK_SIZE (1 << CHUNK_SHIFT) +#define CHUNK_MASK (~(CHUNK_SIZE-1)) +#define NCHUNKS (((PAGE_SIZE - sizeof(struct zbud_page)) & \ + CHUNK_MASK) >> CHUNK_SHIFT) +#define MAX_CHUNK (NCHUNKS-1) + +static struct { + struct list_head list; + unsigned count; +} zbud_unbuddied[NCHUNKS]; +/* list N contains pages with N chunks USED and NCHUNKS-N unused */ +/* element 0 is never used but optimizing that isn't worth it */ +static unsigned long zbud_cumul_chunk_counts[NCHUNKS]; + +struct list_head zbud_buddied_list; +static unsigned long zcache_zbud_buddied_count; + +/* protects the buddied list and all unbuddied lists */ +static DEFINE_SPINLOCK(zbud_budlists_spinlock); + +static LIST_HEAD(zbpg_unused_list); +static unsigned long zcache_zbpg_unused_list_count; + +/* protects the unused page list */ +static DEFINE_SPINLOCK(zbpg_unused_list_spinlock); + +static atomic_t zcache_zbud_curr_raw_pages; +static atomic_t zcache_zbud_curr_zpages; +static unsigned long zcache_zbud_curr_zbytes; +static unsigned long zcache_zbud_cumul_zpages; +static unsigned long zcache_zbud_cumul_zbytes; +static unsigned long zcache_compress_poor; +static unsigned long zcache_mean_compress_poor; + +/* forward references */ +static void *zcache_get_free_page(void); +static void zcache_free_page(void *p); + +/* + * zbud helper functions + */ + +static inline unsigned zbud_max_buddy_size(void) +{ + return MAX_CHUNK << CHUNK_SHIFT; +} + +static inline unsigned zbud_size_to_chunks(unsigned size) +{ + BUG_ON(size == 0 || size > zbud_max_buddy_size()); + return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT; +} + +static inline int zbud_budnum(struct zbud_hdr *zh) +{ + unsigned offset = (unsigned long)zh & (PAGE_SIZE - 1); + struct zbud_page *zbpg = NULL; + unsigned budnum = -1U; + int i; + + for (i = 0; i < ZBUD_MAX_BUDS; i++) + if (offset == offsetof(typeof(*zbpg), buddy[i])) { + budnum = i; + break; + } + BUG_ON(budnum == -1U); + return budnum; +} + +static char *zbud_data(struct zbud_hdr *zh, unsigned size) +{ + struct zbud_page *zbpg; + char *p; + unsigned budnum; + + ASSERT_SENTINEL(zh, ZBH); + budnum = zbud_budnum(zh); + BUG_ON(size == 0 || size > zbud_max_buddy_size()); + zbpg = container_of(zh, struct zbud_page, buddy[budnum]); + ASSERT_SPINLOCK(&zbpg->lock); + p = (char *)zbpg; + if (budnum == 0) + p += ((sizeof(struct zbud_page) + CHUNK_SIZE - 1) & + CHUNK_MASK); + else if (budnum == 1) + p += PAGE_SIZE - ((size + CHUNK_SIZE - 1) & CHUNK_MASK); + return p; +} + +/* + * zbud raw page management + */ + +static struct zbud_page *zbud_alloc_raw_page(void) +{ + struct zbud_page *zbpg = NULL; + struct zbud_hdr *zh0, *zh1; + bool recycled = 0; + + /* if any pages on the zbpg list, use one */ + spin_lock(&zbpg_unused_list_spinlock); + if (!list_empty(&zbpg_unused_list)) { + zbpg = list_first_entry(&zbpg_unused_list, + struct zbud_page, bud_list); + list_del_init(&zbpg->bud_list); + zcache_zbpg_unused_list_count--; + recycled = 1; + } + spin_unlock(&zbpg_unused_list_spinlock); + if (zbpg == NULL) + /* none on zbpg list, try to get a kernel page */ + zbpg = zcache_get_free_page(); + if (likely(zbpg != NULL)) { + INIT_LIST_HEAD(&zbpg->bud_list); + zh0 = &zbpg->buddy[0]; zh1 = &zbpg->buddy[1]; + spin_lock_init(&zbpg->lock); + if (recycled) { + ASSERT_INVERTED_SENTINEL(zbpg, ZBPG); + SET_SENTINEL(zbpg, ZBPG); + BUG_ON(zh0->size != 0 || tmem_oid_valid(&zh0->oid)); + BUG_ON(zh1->size != 0 || tmem_oid_valid(&zh1->oid)); + } else { + atomic_inc(&zcache_zbud_curr_raw_pages); + INIT_LIST_HEAD(&zbpg->bud_list); + SET_SENTINEL(zbpg, ZBPG); + zh0->size = 0; zh1->size = 0; + tmem_oid_set_invalid(&zh0->oid); + tmem_oid_set_invalid(&zh1->oid); + } + } + return zbpg; +} + +static void zbud_free_raw_page(struct zbud_page *zbpg) +{ + struct zbud_hdr *zh0 = &zbpg->buddy[0], *zh1 = &zbpg->buddy[1]; + + ASSERT_SENTINEL(zbpg, ZBPG); + BUG_ON(!list_empty(&zbpg->bud_list)); + ASSERT_SPINLOCK(&zbpg->lock); + BUG_ON(zh0->size != 0 || tmem_oid_valid(&zh0->oid)); + BUG_ON(zh1->size != 0 || tmem_oid_valid(&zh1->oid)); + INVERT_SENTINEL(zbpg, ZBPG); + spin_unlock(&zbpg->lock); + spin_lock(&zbpg_unused_list_spinlock); + list_add(&zbpg->bud_list, &zbpg_unused_list); + zcache_zbpg_unused_list_count++; + spin_unlock(&zbpg_unused_list_spinlock); +} + +/* + * core zbud handling routines + */ + +static unsigned zbud_free(struct zbud_hdr *zh) +{ + unsigned size; + + ASSERT_SENTINEL(zh, ZBH); + BUG_ON(!tmem_oid_valid(&zh->oid)); + size = zh->size; + BUG_ON(zh->size == 0 || zh->size > zbud_max_buddy_size()); + zh->size = 0; + tmem_oid_set_invalid(&zh->oid); + INVERT_SENTINEL(zh, ZBH); + zcache_zbud_curr_zbytes -= size; + atomic_dec(&zcache_zbud_curr_zpages); + return size; +} + +static void zbud_free_and_delist(struct zbud_hdr *zh) +{ + unsigned chunks; + struct zbud_hdr *zh_other; + unsigned budnum = zbud_budnum(zh), size; + struct zbud_page *zbpg = + container_of(zh, struct zbud_page, buddy[budnum]); + + spin_lock(&zbpg->lock); + if (list_empty(&zbpg->bud_list)) { + /* ignore zombie page... see zbud_evict_pages() */ + spin_unlock(&zbpg->lock); + return; + } + size = zbud_free(zh); + ASSERT_SPINLOCK(&zbpg->lock); + zh_other = &zbpg->buddy[(budnum == 0) ? 1 : 0]; + if (zh_other->size == 0) { /* was unbuddied: unlist and free */ + chunks = zbud_size_to_chunks(size) ; + spin_lock(&zbud_budlists_spinlock); + BUG_ON(list_empty(&zbud_unbuddied[chunks].list)); + list_del_init(&zbpg->bud_list); + zbud_unbuddied[chunks].count--; + spin_unlock(&zbud_budlists_spinlock); + zbud_free_raw_page(zbpg); + } else { /* was buddied: move remaining buddy to unbuddied list */ + chunks = zbud_size_to_chunks(zh_other->size) ; + spin_lock(&zbud_budlists_spinlock); + list_del_init(&zbpg->bud_list); + zcache_zbud_buddied_count--; + list_add_tail(&zbpg->bud_list, &zbud_unbuddied[chunks].list); + zbud_unbuddied[chunks].count++; + spin_unlock(&zbud_budlists_spinlock); + spin_unlock(&zbpg->lock); + } +} + +static struct zbud_hdr *zbud_create(uint16_t client_id, uint16_t pool_id, + struct tmem_oid *oid, + uint32_t index, struct page *page, + void *cdata, unsigned size) +{ + struct zbud_hdr *zh0, *zh1, *zh = NULL; + struct zbud_page *zbpg = NULL, *ztmp; + unsigned nchunks; + char *to; + int i, found_good_buddy = 0; + + nchunks = zbud_size_to_chunks(size) ; + for (i = MAX_CHUNK - nchunks + 1; i > 0; i--) { + spin_lock(&zbud_budlists_spinlock); + if (!list_empty(&zbud_unbuddied[i].list)) { + list_for_each_entry_safe(zbpg, ztmp, + &zbud_unbuddied[i].list, bud_list) { + if (spin_trylock(&zbpg->lock)) { + found_good_buddy = i; + goto found_unbuddied; + } + } + } + spin_unlock(&zbud_budlists_spinlock); + } + /* didn't find a good buddy, try allocating a new page */ + zbpg = zbud_alloc_raw_page(); + if (unlikely(zbpg == NULL)) + goto out; + /* ok, have a page, now compress the data before taking locks */ + spin_lock(&zbpg->lock); + spin_lock(&zbud_budlists_spinlock); + list_add_tail(&zbpg->bud_list, &zbud_unbuddied[nchunks].list); + zbud_unbuddied[nchunks].count++; + zh = &zbpg->buddy[0]; + goto init_zh; + +found_unbuddied: + ASSERT_SPINLOCK(&zbpg->lock); + zh0 = &zbpg->buddy[0]; zh1 = &zbpg->buddy[1]; + BUG_ON(!((zh0->size == 0) ^ (zh1->size == 0))); + if (zh0->size != 0) { /* buddy0 in use, buddy1 is vacant */ + ASSERT_SENTINEL(zh0, ZBH); + zh = zh1; + } else if (zh1->size != 0) { /* buddy1 in use, buddy0 is vacant */ + ASSERT_SENTINEL(zh1, ZBH); + zh = zh0; + } else + BUG(); + list_del_init(&zbpg->bud_list); + zbud_unbuddied[found_good_buddy].count--; + list_add_tail(&zbpg->bud_list, &zbud_buddied_list); + zcache_zbud_buddied_count++; + +init_zh: + SET_SENTINEL(zh, ZBH); + zh->size = size; + zh->index = index; + zh->oid = *oid; + zh->pool_id = pool_id; + zh->client_id = client_id; + /* can wait to copy the data until the list locks are dropped */ + spin_unlock(&zbud_budlists_spinlock); + + to = zbud_data(zh, size); + memcpy(to, cdata, size); + spin_unlock(&zbpg->lock); + zbud_cumul_chunk_counts[nchunks]++; + atomic_inc(&zcache_zbud_curr_zpages); + zcache_zbud_cumul_zpages++; + zcache_zbud_curr_zbytes += size; + zcache_zbud_cumul_zbytes += size; +out: + return zh; +} + +static int zbud_decompress(struct page *page, struct zbud_hdr *zh) +{ + struct zbud_page *zbpg; + unsigned budnum = zbud_budnum(zh); + size_t out_len = PAGE_SIZE; + char *to_va, *from_va; + unsigned size; + int ret = 0; + + zbpg = container_of(zh, struct zbud_page, buddy[budnum]); + spin_lock(&zbpg->lock); + if (list_empty(&zbpg->bud_list)) { + /* ignore zombie page... see zbud_evict_pages() */ + ret = -EINVAL; + goto out; + } + ASSERT_SENTINEL(zh, ZBH); + BUG_ON(zh->size == 0 || zh->size > zbud_max_buddy_size()); + to_va = kmap_atomic(page, KM_USER0); + size = zh->size; + from_va = zbud_data(zh, size); + ret = lzo1x_decompress_safe(from_va, size, to_va, &out_len); + BUG_ON(ret != LZO_E_OK); + BUG_ON(out_len != PAGE_SIZE); + kunmap_atomic(to_va, KM_USER0); +out: + spin_unlock(&zbpg->lock); + return ret; +} + +/* + * The following routines handle shrinking of ephemeral pages by evicting + * pages "least valuable" first. + */ + +static unsigned long zcache_evicted_raw_pages; +static unsigned long zcache_evicted_buddied_pages; +static unsigned long zcache_evicted_unbuddied_pages; + +static struct tmem_pool *zcache_get_pool_by_id(uint16_t cli_id, + uint16_t poolid); +static void zcache_put_pool(struct tmem_pool *pool); + +/* + * Flush and free all zbuds in a zbpg, then free the pageframe + */ +static void zbud_evict_zbpg(struct zbud_page *zbpg) +{ + struct zbud_hdr *zh; + int i, j; + uint32_t pool_id[ZBUD_MAX_BUDS], client_id[ZBUD_MAX_BUDS]; + uint32_t index[ZBUD_MAX_BUDS]; + struct tmem_oid oid[ZBUD_MAX_BUDS]; + struct tmem_pool *pool; + + ASSERT_SPINLOCK(&zbpg->lock); + BUG_ON(!list_empty(&zbpg->bud_list)); + for (i = 0, j = 0; i < ZBUD_MAX_BUDS; i++) { + zh = &zbpg->buddy[i]; + if (zh->size) { + client_id[j] = zh->client_id; + pool_id[j] = zh->pool_id; + oid[j] = zh->oid; + index[j] = zh->index; + j++; + zbud_free(zh); + } + } + spin_unlock(&zbpg->lock); + for (i = 0; i < j; i++) { + pool = zcache_get_pool_by_id(client_id[i], pool_id[i]); + if (pool != NULL) { + tmem_flush_page(pool, &oid[i], index[i]); + zcache_put_pool(pool); + } + } + ASSERT_SENTINEL(zbpg, ZBPG); + spin_lock(&zbpg->lock); + zbud_free_raw_page(zbpg); +} + +/* + * Free nr pages. This code is funky because we want to hold the locks + * protecting various lists for as short a time as possible, and in some + * circumstances the list may change asynchronously when the list lock is + * not held. In some cases we also trylock not only to avoid waiting on a + * page in use by another cpu, but also to avoid potential deadlock due to + * lock inversion. + */ +static void zbud_evict_pages(int nr) +{ + struct zbud_page *zbpg; + int i; + + /* first try freeing any pages on unused list */ +retry_unused_list: + spin_lock_bh(&zbpg_unused_list_spinlock); + if (!list_empty(&zbpg_unused_list)) { + /* can't walk list here, since it may change when unlocked */ + zbpg = list_first_entry(&zbpg_unused_list, + struct zbud_page, bud_list); + list_del_init(&zbpg->bud_list); + zcache_zbpg_unused_list_count--; + atomic_dec(&zcache_zbud_curr_raw_pages); + spin_unlock_bh(&zbpg_unused_list_spinlock); + zcache_free_page(zbpg); + zcache_evicted_raw_pages++; + if (--nr <= 0) + goto out; + goto retry_unused_list; + } + spin_unlock_bh(&zbpg_unused_list_spinlock); + + /* now try freeing unbuddied pages, starting with least space avail */ + for (i = 0; i < MAX_CHUNK; i++) { +retry_unbud_list_i: + spin_lock_bh(&zbud_budlists_spinlock); + if (list_empty(&zbud_unbuddied[i].list)) { + spin_unlock_bh(&zbud_budlists_spinlock); + continue; + } + list_for_each_entry(zbpg, &zbud_unbuddied[i].list, bud_list) { + if (unlikely(!spin_trylock(&zbpg->lock))) + continue; + list_del_init(&zbpg->bud_list); + zbud_unbuddied[i].count--; + spin_unlock(&zbud_budlists_spinlock); + zcache_evicted_unbuddied_pages++; + /* want budlists unlocked when doing zbpg eviction */ + zbud_evict_zbpg(zbpg); + local_bh_enable(); + if (--nr <= 0) + goto out; + goto retry_unbud_list_i; + } + spin_unlock_bh(&zbud_budlists_spinlock); + } + + /* as a last resort, free buddied pages */ +retry_bud_list: + spin_lock_bh(&zbud_budlists_spinlock); + if (list_empty(&zbud_buddied_list)) { + spin_unlock_bh(&zbud_budlists_spinlock); + goto out; + } + list_for_each_entry(zbpg, &zbud_buddied_list, bud_list) { + if (unlikely(!spin_trylock(&zbpg->lock))) + continue; + list_del_init(&zbpg->bud_list); + zcache_zbud_buddied_count--; + spin_unlock(&zbud_budlists_spinlock); + zcache_evicted_buddied_pages++; + /* want budlists unlocked when doing zbpg eviction */ + zbud_evict_zbpg(zbpg); + local_bh_enable(); + if (--nr <= 0) + goto out; + goto retry_bud_list; + } + spin_unlock_bh(&zbud_budlists_spinlock); +out: + return; +} + +static void zbud_init(void) +{ + int i; + + INIT_LIST_HEAD(&zbud_buddied_list); + zcache_zbud_buddied_count = 0; + for (i = 0; i < NCHUNKS; i++) { + INIT_LIST_HEAD(&zbud_unbuddied[i].list); + zbud_unbuddied[i].count = 0; + } +} + +#ifdef CONFIG_SYSFS +/* + * These sysfs routines show a nice distribution of how many zbpg's are + * currently (and have ever been placed) in each unbuddied list. It's fun + * to watch but can probably go away before final merge. + */ +static int zbud_show_unbuddied_list_counts(char *buf) +{ + int i; + char *p = buf; + + for (i = 0; i < NCHUNKS; i++) + p += sprintf(p, "%u ", zbud_unbuddied[i].count); + return p - buf; +} + +static int zbud_show_cumul_chunk_counts(char *buf) +{ + unsigned long i, chunks = 0, total_chunks = 0, sum_total_chunks = 0; + unsigned long total_chunks_lte_21 = 0, total_chunks_lte_32 = 0; + unsigned long total_chunks_lte_42 = 0; + char *p = buf; + + for (i = 0; i < NCHUNKS; i++) { + p += sprintf(p, "%lu ", zbud_cumul_chunk_counts[i]); + chunks += zbud_cumul_chunk_counts[i]; + total_chunks += zbud_cumul_chunk_counts[i]; + sum_total_chunks += i * zbud_cumul_chunk_counts[i]; + if (i == 21) + total_chunks_lte_21 = total_chunks; + if (i == 32) + total_chunks_lte_32 = total_chunks; + if (i == 42) + total_chunks_lte_42 = total_chunks; + } + p += sprintf(p, "<=21:%lu <=32:%lu <=42:%lu, mean:%lu\n", + total_chunks_lte_21, total_chunks_lte_32, total_chunks_lte_42, + chunks == 0 ? 0 : sum_total_chunks / chunks); + return p - buf; +} +#endif + +/********** + * This "zv" PAM implementation combines the TLSF-based xvMalloc + * with lzo1x compression to maximize the amount of data that can + * be packed into a physical page. + * + * Zv represents a PAM page with the index and object (plus a "size" value + * necessary for decompression) immediately preceding the compressed data. + */ + +#define ZVH_SENTINEL 0x43214321 + +struct zv_hdr { + uint32_t pool_id; + struct tmem_oid oid; + uint32_t index; + DECL_SENTINEL +}; + +/* rudimentary policy limits */ +/* total number of persistent pages may not exceed this percentage */ +static unsigned int zv_page_count_policy_percent = 75; +/* + * byte count defining poor compression; pages with greater zsize will be + * rejected + */ +static unsigned int zv_max_zsize = (PAGE_SIZE / 8) * 7; +/* + * byte count defining poor *mean* compression; pages with greater zsize + * will be rejected until sufficient better-compressed pages are accepted + * driving the man below this threshold + */ +static unsigned int zv_max_mean_zsize = (PAGE_SIZE / 8) * 5; + +static unsigned long zv_curr_dist_counts[NCHUNKS]; +static unsigned long zv_cumul_dist_counts[NCHUNKS]; + +static struct zv_hdr *zv_create(struct xv_pool *xvpool, uint32_t pool_id, + struct tmem_oid *oid, uint32_t index, + void *cdata, unsigned clen) +{ + struct page *page; + struct zv_hdr *zv = NULL; + uint32_t offset; + int alloc_size = clen + sizeof(struct zv_hdr); + int chunks = (alloc_size + (CHUNK_SIZE - 1)) >> CHUNK_SHIFT; + int ret; + + BUG_ON(!irqs_disabled()); + BUG_ON(chunks >= NCHUNKS); + ret = xv_malloc(xvpool, alloc_size, + &page, &offset, ZCACHE_GFP_MASK); + if (unlikely(ret)) + goto out; + zv_curr_dist_counts[chunks]++; + zv_cumul_dist_counts[chunks]++; + zv = kmap_atomic(page, KM_USER0) + offset; + zv->index = index; + zv->oid = *oid; + zv->pool_id = pool_id; + SET_SENTINEL(zv, ZVH); + memcpy((char *)zv + sizeof(struct zv_hdr), cdata, clen); + kunmap_atomic(zv, KM_USER0); +out: + return zv; +} + +static void zv_free(struct xv_pool *xvpool, struct zv_hdr *zv) +{ + unsigned long flags; + struct page *page; + uint32_t offset; + uint16_t size = xv_get_object_size(zv); + int chunks = (size + (CHUNK_SIZE - 1)) >> CHUNK_SHIFT; + + ASSERT_SENTINEL(zv, ZVH); + BUG_ON(chunks >= NCHUNKS); + zv_curr_dist_counts[chunks]--; + size -= sizeof(*zv); + BUG_ON(size == 0); + INVERT_SENTINEL(zv, ZVH); + page = virt_to_page(zv); + offset = (unsigned long)zv & ~PAGE_MASK; + local_irq_save(flags); + xv_free(xvpool, page, offset); + local_irq_restore(flags); +} + +static void zv_decompress(struct page *page, struct zv_hdr *zv) +{ + size_t clen = PAGE_SIZE; + char *to_va; + unsigned size; + int ret; + + ASSERT_SENTINEL(zv, ZVH); + size = xv_get_object_size(zv) - sizeof(*zv); + BUG_ON(size == 0); + to_va = kmap_atomic(page, KM_USER0); + ret = lzo1x_decompress_safe((char *)zv + sizeof(*zv), + size, to_va, &clen); + kunmap_atomic(to_va, KM_USER0); + BUG_ON(ret != LZO_E_OK); + BUG_ON(clen != PAGE_SIZE); +} + +#ifdef CONFIG_SYSFS +/* + * show a distribution of compression stats for zv pages. + */ + +static int zv_curr_dist_counts_show(char *buf) +{ + unsigned long i, n, chunks = 0, sum_total_chunks = 0; + char *p = buf; + + for (i = 0; i < NCHUNKS; i++) { + n = zv_curr_dist_counts[i]; + p += sprintf(p, "%lu ", n); + chunks += n; + sum_total_chunks += i * n; + } + p += sprintf(p, "mean:%lu\n", + chunks == 0 ? 0 : sum_total_chunks / chunks); + return p - buf; +} + +static int zv_cumul_dist_counts_show(char *buf) +{ + unsigned long i, n, chunks = 0, sum_total_chunks = 0; + char *p = buf; + + for (i = 0; i < NCHUNKS; i++) { + n = zv_cumul_dist_counts[i]; + p += sprintf(p, "%lu ", n); + chunks += n; + sum_total_chunks += i * n; + } + p += sprintf(p, "mean:%lu\n", + chunks == 0 ? 0 : sum_total_chunks / chunks); + return p - buf; +} + +/* + * setting zv_max_zsize via sysfs causes all persistent (e.g. swap) + * pages that don't compress to less than this value (including metadata + * overhead) to be rejected. We don't allow the value to get too close + * to PAGE_SIZE. + */ +static ssize_t zv_max_zsize_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) +{ + return sprintf(buf, "%u\n", zv_max_zsize); +} + +static ssize_t zv_max_zsize_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + unsigned long val; + int err; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + err = strict_strtoul(buf, 10, &val); + if (err || (val == 0) || (val > (PAGE_SIZE / 8) * 7)) + return -EINVAL; + zv_max_zsize = val; + return count; +} + +/* + * setting zv_max_mean_zsize via sysfs causes all persistent (e.g. swap) + * pages that don't compress to less than this value (including metadata + * overhead) to be rejected UNLESS the mean compression is also smaller + * than this value. In other words, we are load-balancing-by-zsize the + * accepted pages. Again, we don't allow the value to get too close + * to PAGE_SIZE. + */ +static ssize_t zv_max_mean_zsize_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) +{ + return sprintf(buf, "%u\n", zv_max_mean_zsize); +} + +static ssize_t zv_max_mean_zsize_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + unsigned long val; + int err; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + err = strict_strtoul(buf, 10, &val); + if (err || (val == 0) || (val > (PAGE_SIZE / 8) * 7)) + return -EINVAL; + zv_max_mean_zsize = val; + return count; +} + +/* + * setting zv_page_count_policy_percent via sysfs sets an upper bound of + * persistent (e.g. swap) pages that will be retained according to: + * (zv_page_count_policy_percent * totalram_pages) / 100) + * when that limit is reached, further puts will be rejected (until + * some pages have been flushed). Note that, due to compression, + * this number may exceed 100; it defaults to 75 and we set an + * arbitary limit of 150. A poor choice will almost certainly result + * in OOM's, so this value should only be changed prudently. + */ +static ssize_t zv_page_count_policy_percent_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) +{ + return sprintf(buf, "%u\n", zv_page_count_policy_percent); +} + +static ssize_t zv_page_count_policy_percent_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + unsigned long val; + int err; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + err = strict_strtoul(buf, 10, &val); + if (err || (val == 0) || (val > 150)) + return -EINVAL; + zv_page_count_policy_percent = val; + return count; +} + +static struct kobj_attribute zcache_zv_max_zsize_attr = { + .attr = { .name = "zv_max_zsize", .mode = 0644 }, + .show = zv_max_zsize_show, + .store = zv_max_zsize_store, +}; + +static struct kobj_attribute zcache_zv_max_mean_zsize_attr = { + .attr = { .name = "zv_max_mean_zsize", .mode = 0644 }, + .show = zv_max_mean_zsize_show, + .store = zv_max_mean_zsize_store, +}; + +static struct kobj_attribute zcache_zv_page_count_policy_percent_attr = { + .attr = { .name = "zv_page_count_policy_percent", + .mode = 0644 }, + .show = zv_page_count_policy_percent_show, + .store = zv_page_count_policy_percent_store, +}; +#endif + +/* + * zcache core code starts here + */ + +/* useful stats not collected by cleancache or frontswap */ +static unsigned long zcache_flush_total; +static unsigned long zcache_flush_found; +static unsigned long zcache_flobj_total; +static unsigned long zcache_flobj_found; +static unsigned long zcache_failed_eph_puts; +static unsigned long zcache_failed_pers_puts; + +/* + * Tmem operations assume the poolid implies the invoking client. + * Zcache only has one client (the kernel itself): LOCAL_CLIENT. + * RAMster has each client numbered by cluster node, and a KVM version + * of zcache would have one client per guest and each client might + * have a poolid==N. + */ +static struct tmem_pool *zcache_get_pool_by_id(uint16_t cli_id, uint16_t poolid) +{ + struct tmem_pool *pool = NULL; + struct zcache_client *cli = NULL; + + if (cli_id == LOCAL_CLIENT) + cli = &zcache_host; + else { + if (cli_id >= MAX_CLIENTS) + goto out; + cli = &zcache_clients[cli_id]; + if (cli == NULL) + goto out; + atomic_inc(&cli->refcount); + } + if (poolid < MAX_POOLS_PER_CLIENT) { + pool = cli->tmem_pools[poolid]; + if (pool != NULL) + atomic_inc(&pool->refcount); + } +out: + return pool; +} + +static void zcache_put_pool(struct tmem_pool *pool) +{ + struct zcache_client *cli = NULL; + + if (pool == NULL) + BUG(); + cli = pool->client; + atomic_dec(&pool->refcount); + atomic_dec(&cli->refcount); +} + +int zcache_new_client(uint16_t cli_id) +{ + struct zcache_client *cli = NULL; + int ret = -1; + + if (cli_id == LOCAL_CLIENT) + cli = &zcache_host; + else if ((unsigned int)cli_id < MAX_CLIENTS) + cli = &zcache_clients[cli_id]; + if (cli == NULL) + goto out; + if (cli->allocated) + goto out; + cli->allocated = 1; +#ifdef CONFIG_FRONTSWAP + cli->xvpool = xv_create_pool(); + if (cli->xvpool == NULL) + goto out; +#endif + ret = 0; +out: + return ret; +} + +/* counters for debugging */ +static unsigned long zcache_failed_get_free_pages; +static unsigned long zcache_failed_alloc; +static unsigned long zcache_put_to_flush; +static unsigned long zcache_aborted_preload; +static unsigned long zcache_aborted_shrink; + +/* + * Ensure that memory allocation requests in zcache don't result + * in direct reclaim requests via the shrinker, which would cause + * an infinite loop. Maybe a GFP flag would be better? + */ +static DEFINE_SPINLOCK(zcache_direct_reclaim_lock); + +/* + * for now, used named slabs so can easily track usage; later can + * either just use kmalloc, or perhaps add a slab-like allocator + * to more carefully manage total memory utilization + */ +static struct kmem_cache *zcache_objnode_cache; +static struct kmem_cache *zcache_obj_cache; +static atomic_t zcache_curr_obj_count = ATOMIC_INIT(0); +static unsigned long zcache_curr_obj_count_max; +static atomic_t zcache_curr_objnode_count = ATOMIC_INIT(0); +static unsigned long zcache_curr_objnode_count_max; + +/* + * to avoid memory allocation recursion (e.g. due to direct reclaim), we + * preload all necessary data structures so the hostops callbacks never + * actually do a malloc + */ +struct zcache_preload { + void *page; + struct tmem_obj *obj; + int nr; + struct tmem_objnode *objnodes[OBJNODE_TREE_MAX_PATH]; +}; +static DEFINE_PER_CPU(struct zcache_preload, zcache_preloads) = { 0, }; + +static int zcache_do_preload(struct tmem_pool *pool) +{ + struct zcache_preload *kp; + struct tmem_objnode *objnode; + struct tmem_obj *obj; + void *page; + int ret = -ENOMEM; + + if (unlikely(zcache_objnode_cache == NULL)) + goto out; + if (unlikely(zcache_obj_cache == NULL)) + goto out; + if (!spin_trylock(&zcache_direct_reclaim_lock)) { + zcache_aborted_preload++; + goto out; + } + preempt_disable(); + kp = &__get_cpu_var(zcache_preloads); + while (kp->nr < ARRAY_SIZE(kp->objnodes)) { + preempt_enable_no_resched(); + objnode = kmem_cache_alloc(zcache_objnode_cache, + ZCACHE_GFP_MASK); + if (unlikely(objnode == NULL)) { + zcache_failed_alloc++; + goto unlock_out; + } + preempt_disable(); + kp = &__get_cpu_var(zcache_preloads); + if (kp->nr < ARRAY_SIZE(kp->objnodes)) + kp->objnodes[kp->nr++] = objnode; + else + kmem_cache_free(zcache_objnode_cache, objnode); + } + preempt_enable_no_resched(); + obj = kmem_cache_alloc(zcache_obj_cache, ZCACHE_GFP_MASK); + if (unlikely(obj == NULL)) { + zcache_failed_alloc++; + goto unlock_out; + } + page = (void *)__get_free_page(ZCACHE_GFP_MASK); + if (unlikely(page == NULL)) { + zcache_failed_get_free_pages++; + kmem_cache_free(zcache_obj_cache, obj); + goto unlock_out; + } + preempt_disable(); + kp = &__get_cpu_var(zcache_preloads); + if (kp->obj == NULL) + kp->obj = obj; + else + kmem_cache_free(zcache_obj_cache, obj); + if (kp->page == NULL) + kp->page = page; + else + free_page((unsigned long)page); + ret = 0; +unlock_out: + spin_unlock(&zcache_direct_reclaim_lock); +out: + return ret; +} + +static void *zcache_get_free_page(void) +{ + struct zcache_preload *kp; + void *page; + + kp = &__get_cpu_var(zcache_preloads); + page = kp->page; + BUG_ON(page == NULL); + kp->page = NULL; + return page; +} + +static void zcache_free_page(void *p) +{ + free_page((unsigned long)p); +} + +/* + * zcache implementation for tmem host ops + */ + +static struct tmem_objnode *zcache_objnode_alloc(struct tmem_pool *pool) +{ + struct tmem_objnode *objnode = NULL; + unsigned long count; + struct zcache_preload *kp; + + kp = &__get_cpu_var(zcache_preloads); + if (kp->nr <= 0) + goto out; + objnode = kp->objnodes[kp->nr - 1]; + BUG_ON(objnode == NULL); + kp->objnodes[kp->nr - 1] = NULL; + kp->nr--; + count = atomic_inc_return(&zcache_curr_objnode_count); + if (count > zcache_curr_objnode_count_max) + zcache_curr_objnode_count_max = count; +out: + return objnode; +} + +static void zcache_objnode_free(struct tmem_objnode *objnode, + struct tmem_pool *pool) +{ + atomic_dec(&zcache_curr_objnode_count); + BUG_ON(atomic_read(&zcache_curr_objnode_count) < 0); + kmem_cache_free(zcache_objnode_cache, objnode); +} + +static struct tmem_obj *zcache_obj_alloc(struct tmem_pool *pool) +{ + struct tmem_obj *obj = NULL; + unsigned long count; + struct zcache_preload *kp; + + kp = &__get_cpu_var(zcache_preloads); + obj = kp->obj; + BUG_ON(obj == NULL); + kp->obj = NULL; + count = atomic_inc_return(&zcache_curr_obj_count); + if (count > zcache_curr_obj_count_max) + zcache_curr_obj_count_max = count; + return obj; +} + +static void zcache_obj_free(struct tmem_obj *obj, struct tmem_pool *pool) +{ + atomic_dec(&zcache_curr_obj_count); + BUG_ON(atomic_read(&zcache_curr_obj_count) < 0); + kmem_cache_free(zcache_obj_cache, obj); +} + +static struct tmem_hostops zcache_hostops = { + .obj_alloc = zcache_obj_alloc, + .obj_free = zcache_obj_free, + .objnode_alloc = zcache_objnode_alloc, + .objnode_free = zcache_objnode_free, +}; + +/* + * zcache implementations for PAM page descriptor ops + */ + +static atomic_t zcache_curr_eph_pampd_count = ATOMIC_INIT(0); +static unsigned long zcache_curr_eph_pampd_count_max; +static atomic_t zcache_curr_pers_pampd_count = ATOMIC_INIT(0); +static unsigned long zcache_curr_pers_pampd_count_max; + +/* forward reference */ +static int zcache_compress(struct page *from, void **out_va, size_t *out_len); + +static void *zcache_pampd_create(char *data, size_t size, bool raw, int eph, + struct tmem_pool *pool, struct tmem_oid *oid, + uint32_t index) +{ + void *pampd = NULL, *cdata; + size_t clen; + int ret; + unsigned long count; + struct page *page = virt_to_page(data); + struct zcache_client *cli = pool->client; 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