diff options
| -rw-r--r-- | fs/nfsd/nfscache.c | 44 |
1 files changed, 29 insertions, 15 deletions
diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c index 17cb0d6b9944..eb2587745a64 100644 --- a/fs/nfsd/nfscache.c +++ b/fs/nfsd/nfscache.c @@ -11,6 +11,8 @@ #include <linux/slab.h> #include <linux/sunrpc/addr.h> #include <linux/highmem.h> +#include <linux/log2.h> +#include <linux/hash.h> #include <net/checksum.h> #include "nfsd.h" @@ -18,7 +20,12 @@ #define NFSDDBG_FACILITY NFSDDBG_REPCACHE -#define HASHSIZE 64 +/* + * We use this value to determine the number of hash buckets from the max + * cache size, the idea being that when the cache is at its maximum number + * of entries, then this should be the average number of entries per bucket. + */ +#define TARGET_BUCKET_SIZE 64 static struct hlist_head * cache_hash; static struct list_head lru_head; @@ -27,6 +34,9 @@ static struct kmem_cache *drc_slab; /* max number of entries allowed in the cache */ static unsigned int max_drc_entries; +/* number of significant bits in the hash value */ +static unsigned int maskbits; + /* * Stats and other tracking of on the duplicate reply cache. All of these and * the "rc" fields in nfsdstats are protected by the cache_lock @@ -47,16 +57,6 @@ static unsigned int longest_chain; /* size of cache when we saw the longest hash chain */ static unsigned int longest_chain_cachesize; -/* - * Calculate the hash index from an XID. - */ -static inline u32 request_hash(u32 xid) -{ - u32 h = xid; - h ^= (xid >> 24); - return h & (HASHSIZE-1); -} - static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec); static void cache_cleaner_func(struct work_struct *unused); static int nfsd_reply_cache_shrink(struct shrinker *shrink, @@ -103,6 +103,16 @@ nfsd_cache_size_limit(void) return min_t(unsigned int, limit, 256*1024); } +/* + * Compute the number of hash buckets we need. Divide the max cachesize by + * the "target" max bucket size, and round up to next power of two. + */ +static unsigned int +nfsd_hashsize(unsigned int limit) +{ + return roundup_pow_of_two(limit / TARGET_BUCKET_SIZE); +} + static struct svc_cacherep * nfsd_reply_cache_alloc(void) { @@ -143,9 +153,13 @@ nfsd_reply_cache_free(struct svc_cacherep *rp) int nfsd_reply_cache_init(void) { + unsigned int hashsize; + INIT_LIST_HEAD(&lru_head); max_drc_entries = nfsd_cache_size_limit(); num_drc_entries = 0; + hashsize = nfsd_hashsize(max_drc_entries); + maskbits = ilog2(hashsize); register_shrinker(&nfsd_reply_cache_shrinker); drc_slab = kmem_cache_create("nfsd_drc", sizeof(struct svc_cacherep), @@ -153,7 +167,7 @@ int nfsd_reply_cache_init(void) if (!drc_slab) goto out_nomem; - cache_hash = kcalloc(HASHSIZE, sizeof(struct hlist_head), GFP_KERNEL); + cache_hash = kcalloc(hashsize, sizeof(struct hlist_head), GFP_KERNEL); if (!cache_hash) goto out_nomem; @@ -204,7 +218,7 @@ static void hash_refile(struct svc_cacherep *rp) { hlist_del_init(&rp->c_hash); - hlist_add_head(&rp->c_hash, cache_hash + request_hash(rp->c_xid)); + hlist_add_head(&rp->c_hash, cache_hash + hash_32(rp->c_xid, maskbits)); } static inline bool @@ -329,7 +343,7 @@ nfsd_cache_search(struct svc_rqst *rqstp, __wsum csum) struct hlist_head *rh; unsigned int entries = 0; - rh = &cache_hash[request_hash(rqstp->rq_xid)]; + rh = &cache_hash[hash_32(rqstp->rq_xid, maskbits)]; hlist_for_each_entry(rp, rh, c_hash) { ++entries; if (nfsd_cache_match(rqstp, csum, rp)) { @@ -588,7 +602,7 @@ static int nfsd_reply_cache_stats_show(struct seq_file *m, void *v) spin_lock(&cache_lock); seq_printf(m, "max entries: %u\n", max_drc_entries); seq_printf(m, "num entries: %u\n", num_drc_entries); - seq_printf(m, "hash buckets: %u\n", HASHSIZE); + seq_printf(m, "hash buckets: %u\n", 1 << maskbits); seq_printf(m, "mem usage: %u\n", drc_mem_usage); seq_printf(m, "cache hits: %u\n", nfsdstats.rchits); seq_printf(m, "cache misses: %u\n", nfsdstats.rcmisses); |