Simplify the duplicate replay cache by initialising the preallocated
cache entry, so that we can use it as a key for the cache lookup.
Note that the 99.999% case we want to optimise for is still the one
where the lookup fails, and we have to add this entry to the cache,
so preinitialising should not cause a performance penalty.
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
---
fs/nfsd/cache.h | 6 +--
fs/nfsd/nfscache.c | 94 ++++++++++++++++++++++------------------------
2 files changed, 47 insertions(+), 53 deletions(-)
diff --git a/fs/nfsd/cache.h b/fs/nfsd/cache.h
index b7559c6f2b97..bd77d5f6fe53 100644
--- a/fs/nfsd/cache.h
+++ b/fs/nfsd/cache.h
@@ -24,13 +24,13 @@ struct svc_cacherep {
unsigned char c_state, /* unused, inprog, done */
c_type, /* status, buffer */
c_secure : 1; /* req came from port < 1024 */
- struct sockaddr_in6 c_addr;
__be32 c_xid;
- u32 c_prot;
+ __wsum c_csum;
u32 c_proc;
+ u32 c_prot;
u32 c_vers;
unsigned int c_len;
- __wsum c_csum;
+ struct sockaddr_in6 c_addr;
unsigned long c_timestamp;
union {
struct kvec u_vec;
diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index cef4686f87ef..527ce4c65765 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -121,7 +121,7 @@ nfsd_cache_hash(__be32 xid)
}
static struct svc_cacherep *
-nfsd_reply_cache_alloc(void)
+nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum)
{
struct svc_cacherep *rp;
@@ -130,6 +130,16 @@ nfsd_reply_cache_alloc(void)
rp->c_state = RC_UNUSED;
rp->c_type = RC_NOCACHE;
INIT_LIST_HEAD(&rp->c_lru);
+
+ rp->c_xid = rqstp->rq_xid;
+ rp->c_proc = rqstp->rq_proc;
+ memset(&rp->c_addr, 0, sizeof(rp->c_addr));
+ rpc_copy_addr((struct sockaddr *)&rp->c_addr, svc_addr(rqstp));
+ rpc_set_port((struct sockaddr *)&rp->c_addr, rpc_get_port(svc_addr(rqstp)));
+ rp->c_prot = rqstp->rq_prot;
+ rp->c_vers = rqstp->rq_vers;
+ rp->c_len = rqstp->rq_arg.len;
+ rp->c_csum = csum;
}
return rp;
}
@@ -141,9 +151,11 @@ nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
drc_mem_usage -= rp->c_replvec.iov_len;
kfree(rp->c_replvec.iov_base);
}
- list_del(&rp->c_lru);
- atomic_dec(&num_drc_entries);
- drc_mem_usage -= sizeof(*rp);
+ if (rp->c_state != RC_UNUSED) {
+ list_del(&rp->c_lru);
+ atomic_dec(&num_drc_entries);
+ drc_mem_usage -= sizeof(*rp);
+ }
kmem_cache_free(drc_slab, rp);
}
@@ -319,24 +331,23 @@ nfsd_cache_csum(struct svc_rqst *rqstp)
}
static bool
-nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
+nfsd_cache_match(const struct svc_cacherep *key, const struct svc_cacherep *rp)
{
/* Check RPC XID first */
- if (rqstp->rq_xid != rp->c_xid)
+ if (key->c_xid != rp->c_xid)
return false;
/* compare checksum of NFS data */
- if (csum != rp->c_csum) {
+ if (key->c_csum != rp->c_csum) {
++payload_misses;
return false;
}
/* Other discriminators */
- if (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))
+ if (key->c_proc != rp->c_proc ||
+ key->c_prot != rp->c_prot ||
+ key->c_vers != rp->c_vers ||
+ key->c_len != rp->c_len ||
+ memcmp(&key->c_addr, &rp->c_addr, sizeof(key->c_addr)) != 0)
return false;
return true;
@@ -345,19 +356,18 @@ nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
/*
* Search the request hash for an entry that matches the given rqstp.
* Must be called with cache_lock held. Returns the found entry or
- * NULL on failure.
+ * inserts an empty key on failure.
*/
static struct svc_cacherep *
-nfsd_cache_search(struct nfsd_drc_bucket *b, struct svc_rqst *rqstp,
- __wsum csum)
+nfsd_cache_insert(struct nfsd_drc_bucket *b, struct svc_cacherep *key)
{
- struct svc_cacherep *rp, *ret = NULL;
+ struct svc_cacherep *rp, *ret = key;
struct list_head *rh = &b->lru_head;
unsigned int entries = 0;
list_for_each_entry(rp, rh, c_lru) {
++entries;
- if (nfsd_cache_match(rqstp, csum, rp)) {
+ if (nfsd_cache_match(key, rp)) {
ret = rp;
break;
}
@@ -374,6 +384,7 @@ nfsd_cache_search(struct nfsd_drc_bucket *b, struct svc_rqst *rqstp,
atomic_read(&num_drc_entries));
}
+ lru_put_end(b, ret);
return ret;
}
@@ -389,9 +400,6 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
{
struct svc_cacherep *rp, *found;
__be32 xid = rqstp->rq_xid;
- u32 proto = rqstp->rq_prot,
- vers = rqstp->rq_vers,
- proc = rqstp->rq_proc;
__wsum csum;
u32 hash = nfsd_cache_hash(xid);
struct nfsd_drc_bucket *b = &drc_hashtbl[hash];
@@ -410,52 +418,38 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
* Since the common case is a cache miss followed by an insert,
* preallocate an entry.
*/
- rp = nfsd_reply_cache_alloc();
- spin_lock(&b->cache_lock);
- if (likely(rp)) {
- atomic_inc(&num_drc_entries);
- drc_mem_usage += sizeof(*rp);
+ rp = nfsd_reply_cache_alloc(rqstp, csum);
+ if (!rp) {
+ dprintk("nfsd: unable to allocate DRC entry!\n");
+ return rtn;
}
- /* go ahead and prune the cache */
- prune_bucket(b);
-
- found = nfsd_cache_search(b, rqstp, csum);
- if (found) {
- if (likely(rp))
- nfsd_reply_cache_free_locked(rp);
+ spin_lock(&b->cache_lock);
+ found = nfsd_cache_insert(b, rp);
+ if (found != rp) {
+ nfsd_reply_cache_free_locked(rp);
rp = found;
goto found_entry;
}
- if (!rp) {
- dprintk("nfsd: unable to allocate DRC entry!\n");
- goto out;
- }
-
nfsdstats.rcmisses++;
rqstp->rq_cacherep = rp;
rp->c_state = RC_INPROG;
- rp->c_xid = xid;
- rp->c_proc = proc;
- rpc_copy_addr((struct sockaddr *)&rp->c_addr, svc_addr(rqstp));
- rpc_set_port((struct sockaddr *)&rp->c_addr, rpc_get_port(svc_addr(rqstp)));
- rp->c_prot = proto;
- rp->c_vers = vers;
- rp->c_len = rqstp->rq_arg.len;
- rp->c_csum = csum;
- lru_put_end(b, rp);
+ atomic_inc(&num_drc_entries);
+ drc_mem_usage += sizeof(*rp);
+
+ /* go ahead and prune the cache */
+ prune_bucket(b);
out:
spin_unlock(&b->cache_lock);
return rtn;
found_entry:
- nfsdstats.rchits++;
/* We found a matching entry which is either in progress or done. */
- lru_put_end(b, rp);
-
+ nfsdstats.rchits++;
rtn = RC_DROPIT;
+
/* Request being processed */
if (rp->c_state == RC_INPROG)
goto out;
--
2.17.1
