#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"
#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;
static struct kmem_cache *drc_slab;
-static unsigned int num_drc_entries;
+
+/* 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;
+
/*
- * Calculate the hash index from an XID.
+ * 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
*/
-static inline u32 request_hash(u32 xid)
-{
- u32 h = xid;
- h ^= (xid >> 24);
- return h & (HASHSIZE-1);
-}
+
+/* total number of entries */
+static unsigned int num_drc_entries;
+
+/* cache misses due only to checksum comparison failures */
+static unsigned int payload_misses;
+
+/* amount of memory (in bytes) currently consumed by the DRC */
+static unsigned int drc_mem_usage;
+
+/* longest hash chain seen */
+static unsigned int longest_chain;
+
+/* size of cache when we saw the longest hash chain */
+static unsigned int longest_chain_cachesize;
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,
struct shrink_control *sc);
-struct shrinker nfsd_reply_cache_shrinker = {
+static struct shrinker nfsd_reply_cache_shrinker = {
.shrink = nfsd_reply_cache_shrink,
.seeks = 1,
};
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)
{
static void
nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
{
- if (rp->c_type == RC_REPLBUFF)
+ if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base) {
+ drc_mem_usage -= rp->c_replvec.iov_len;
kfree(rp->c_replvec.iov_base);
+ }
if (!hlist_unhashed(&rp->c_hash))
hlist_del(&rp->c_hash);
list_del(&rp->c_lru);
--num_drc_entries;
+ drc_mem_usage -= sizeof(*rp);
kmem_cache_free(drc_slab, 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),
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;
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
return csum;
}
+static bool
+nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
+{
+ /* Check RPC header info first */
+ if (rqstp->rq_xid != rp->c_xid || rqstp->rq_proc != rp->c_proc ||
+ rqstp->rq_prot != rp->c_prot || rqstp->rq_vers != rp->c_vers ||
+ rqstp->rq_arg.len != rp->c_len ||
+ !rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) ||
+ rpc_get_port(svc_addr(rqstp)) != rpc_get_port((struct sockaddr *)&rp->c_addr))
+ return false;
+
+ /* compare checksum of NFS data */
+ if (csum != rp->c_csum) {
+ ++payload_misses;
+ return false;
+ }
+
+ return true;
+}
+
/*
* Search the request hash for an entry that matches the given rqstp.
* Must be called with cache_lock held. Returns the found entry or
static struct svc_cacherep *
nfsd_cache_search(struct svc_rqst *rqstp, __wsum csum)
{
- struct svc_cacherep *rp;
+ struct svc_cacherep *rp, *ret = NULL;
struct hlist_head *rh;
- __be32 xid = rqstp->rq_xid;
- u32 proto = rqstp->rq_prot,
- vers = rqstp->rq_vers,
- proc = rqstp->rq_proc;
+ unsigned int entries = 0;
- rh = &cache_hash[request_hash(xid)];
+ rh = &cache_hash[hash_32(rqstp->rq_xid, maskbits)];
hlist_for_each_entry(rp, rh, c_hash) {
- if (xid == rp->c_xid && proc == rp->c_proc &&
- proto == rp->c_prot && vers == rp->c_vers &&
- rqstp->rq_arg.len == rp->c_len && csum == rp->c_csum &&
- rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) &&
- rpc_get_port(svc_addr(rqstp)) == rpc_get_port((struct sockaddr *)&rp->c_addr))
- return rp;
+ ++entries;
+ if (nfsd_cache_match(rqstp, csum, rp)) {
+ ret = rp;
+ break;
+ }
}
- return NULL;
+
+ /* tally hash chain length stats */
+ if (entries > longest_chain) {
+ longest_chain = entries;
+ longest_chain_cachesize = num_drc_entries;
+ } else if (entries == longest_chain) {
+ /* prefer to keep the smallest cachesize possible here */
+ longest_chain_cachesize = min(longest_chain_cachesize,
+ num_drc_entries);
+ }
+
+ return ret;
}
/*
__wsum csum;
unsigned long age;
int type = rqstp->rq_cachetype;
- int rtn;
+ int rtn = RC_DOIT;
rqstp->rq_cacherep = NULL;
if (type == RC_NOCACHE) {
nfsdstats.rcnocache++;
- return RC_DOIT;
+ return rtn;
}
csum = nfsd_cache_csum(rqstp);
+ /*
+ * Since the common case is a cache miss followed by an insert,
+ * preallocate an entry. First, try to reuse the first entry on the LRU
+ * if it works, then go ahead and prune the LRU list.
+ */
spin_lock(&cache_lock);
- rtn = RC_DOIT;
-
- rp = nfsd_cache_search(rqstp, csum);
- if (rp)
- goto found_entry;
-
- /* Try to use the first entry on the LRU */
if (!list_empty(&lru_head)) {
rp = list_first_entry(&lru_head, struct svc_cacherep, c_lru);
if (nfsd_cache_entry_expired(rp) ||
num_drc_entries >= max_drc_entries) {
lru_put_end(rp);
prune_cache_entries();
- goto setup_entry;
+ goto search_cache;
}
}
- /* Drop the lock and allocate a new entry */
+ /* No expired ones available, allocate a new one. */
spin_unlock(&cache_lock);
rp = nfsd_reply_cache_alloc();
- if (!rp) {
- dprintk("nfsd: unable to allocate DRC entry!\n");
- return RC_DOIT;
- }
spin_lock(&cache_lock);
- ++num_drc_entries;
+ if (likely(rp)) {
+ ++num_drc_entries;
+ drc_mem_usage += sizeof(*rp);
+ }
- /*
- * Must search again just in case someone inserted one
- * after we dropped the lock above.
- */
+search_cache:
found = nfsd_cache_search(rqstp, csum);
if (found) {
- nfsd_reply_cache_free_locked(rp);
+ if (likely(rp))
+ nfsd_reply_cache_free_locked(rp);
rp = found;
goto found_entry;
}
+ if (!rp) {
+ dprintk("nfsd: unable to allocate DRC entry!\n");
+ goto out;
+ }
+
/*
* We're keeping the one we just allocated. Are we now over the
* limit? Prune one off the tip of the LRU in trade for the one we
nfsd_reply_cache_free_locked(list_first_entry(&lru_head,
struct svc_cacherep, c_lru));
-setup_entry:
nfsdstats.rcmisses++;
rqstp->rq_cacherep = rp;
rp->c_state = RC_INPROG;
/* release any buffer */
if (rp->c_type == RC_REPLBUFF) {
+ drc_mem_usage -= rp->c_replvec.iov_len;
kfree(rp->c_replvec.iov_base);
rp->c_replvec.iov_base = NULL;
}
struct svc_cacherep *rp = rqstp->rq_cacherep;
struct kvec *resv = &rqstp->rq_res.head[0], *cachv;
int len;
+ size_t bufsize = 0;
if (!rp)
return;
break;
case RC_REPLBUFF:
cachv = &rp->c_replvec;
- cachv->iov_base = kmalloc(len << 2, GFP_KERNEL);
+ bufsize = len << 2;
+ cachv->iov_base = kmalloc(bufsize, GFP_KERNEL);
if (!cachv->iov_base) {
nfsd_reply_cache_free(rp);
return;
}
- cachv->iov_len = len << 2;
- memcpy(cachv->iov_base, statp, len << 2);
+ cachv->iov_len = bufsize;
+ memcpy(cachv->iov_base, statp, bufsize);
break;
case RC_NOCACHE:
nfsd_reply_cache_free(rp);
return;
}
spin_lock(&cache_lock);
+ drc_mem_usage += bufsize;
lru_put_end(rp);
rp->c_secure = rqstp->rq_secure;
rp->c_type = cachetype;
vec->iov_len += data->iov_len;
return 1;
}
+
+/*
+ * Note that fields may be added, removed or reordered in the future. Programs
+ * scraping this file for info should test the labels to ensure they're
+ * getting the correct field.
+ */
+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", 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);
+ seq_printf(m, "not cached: %u\n", nfsdstats.rcnocache);
+ seq_printf(m, "payload misses: %u\n", payload_misses);
+ seq_printf(m, "longest chain len: %u\n", longest_chain);
+ seq_printf(m, "cachesize at longest: %u\n", longest_chain_cachesize);
+ spin_unlock(&cache_lock);
+ return 0;
+}
+
+int nfsd_reply_cache_stats_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, nfsd_reply_cache_stats_show, NULL);
+}
projects / ~andy / linux / blobdiff