path: root/fs/nfs/nfs4_fs.h
diff options
authorChuck Lever <chuck.lever@oracle.com>2011-12-06 16:13:48 -0500
committerTrond Myklebust <Trond.Myklebust@netapp.com>2012-01-05 11:59:18 -0500
commit0aaaf5c424c7ffd6b0c4253251356558b16ef3a2 (patch)
tree8ef0eebc41a8e247d52280fd79d36934a71fcb00 /fs/nfs/nfs4_fs.h
parent414adf14cd3b52e411f79d941a15d0fd4af427fc (diff)
NFS: Cache state owners after files are closed
Servers have a finite amount of memory to store NFSv4 open and lock owners. Moreover, servers may have a difficult time determining when they can reap their state owner table, thanks to gray areas in the NFSv4 protocol specification. Thus clients should be careful to reuse state owners when possible. Currently Linux is not too careful. When a user has closed all her files on one mount point, the state owner's reference count goes to zero, and it is released. The next OPEN allocates a new one. A workload that serially opens and closes files can run through a large number of open owners this way. When a state owner's reference count goes to zero, slap it onto a free list for that nfs_server, with an expiry time. Garbage collect before looking for a state owner. This makes state owners for active users available for re-use. Now that there can be unused state owners remaining at umount time, purge the state owner free list when a server is destroyed. Also be sure not to reclaim unused state owners during state recovery. This change has benefits for the client as well. For some workloads, this approach drops the number of OPEN_CONFIRM calls from the same as the number of OPEN calls, down to just one. This reduces wire traffic and thus open(2) latency. Before this patch, untarring a kernel source tarball shows the OPEN_CONFIRM call counter steadily increasing through the test. With the patch, the OPEN_CONFIRM count remains at 1 throughout the entire untar. As long as the expiry time is kept short, I don't think garbage collection should be terribly expensive, although it does bounce the clp->cl_lock around a bit. [ At some point we should rationalize the use of the nfs_server ->destroy method. ] Signed-off-by: Chuck Lever <chuck.lever@oracle.com> [Trond: Fixed a garbage collection race and a few efficiency issues] Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'fs/nfs/nfs4_fs.h')
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 693ae22f8731..4d7d0aedc101 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -94,6 +94,8 @@ struct nfs_unique_id {
struct nfs4_state_owner {
struct nfs_unique_id so_owner_id;
struct nfs_server *so_server;
+ struct list_head so_lru;
+ unsigned long so_expires;
struct rb_node so_server_node;
struct rpc_cred *so_cred; /* Associated cred */
@@ -319,6 +321,7 @@ static inline void nfs4_schedule_session_recovery(struct nfs4_session *session)
extern struct nfs4_state_owner * nfs4_get_state_owner(struct nfs_server *, struct rpc_cred *);
extern void nfs4_put_state_owner(struct nfs4_state_owner *);
+extern void nfs4_purge_state_owners(struct nfs_server *);
extern struct nfs4_state * nfs4_get_open_state(struct inode *, struct nfs4_state_owner *);
extern void nfs4_put_open_state(struct nfs4_state *);
extern void nfs4_close_state(struct nfs4_state *, fmode_t);