On Mon, Oct 01, 2018 at 10:41:55AM -0400, Trond Myklebust wrote:
> 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;
Unless I've missed something subtle--I'll move this chunk into the next
patch.--b.
> 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
