Testing has shown that the pool->sp_lock can be a bottleneck on a busy
server. Every time data is received on a socket, the server must take
that lock in order to dequeue a thread from the sp_threads list.
Address this problem by eliminating the sp_threads list (which contains
threads that are currently idle) and replacing it with a RQ_BUSY flag in
svc_rqst. This allows us to walk the sp_all_threads list under the
rcu_read_lock and find a suitable thread for the xprt by doing a
test_and_set_bit.
Note that we do still have a potential atomicity problem however with
this approach. We don't want svc_xprt_do_enqueue to set the
rqst->rq_xprt pointer unless a test_and_set_bit of RQ_BUSY returned
zero (which indicates that the thread was idle). But, by the time we
check that, the bit could be flipped by a waking thread.
To address this, we acquire a new per-rqst spinlock (rq_lock) and take
that before doing the test_and_set_bit. If that returns false, then we
can set rq_xprt and drop the spinlock. Then, when the thread wakes up,
it must set the bit under the same spinlock and can trust that if it was
already set then the rq_xprt is also properly set.
With this scheme, the case where we have an idle thread no longer needs
to take the highly contended pool->sp_lock at all, and that removes the
bottleneck.
That still leaves one issue: What of the case where we walk the whole
sp_all_threads list and don't find an idle thread? Because the search is
lockess, it's possible for the queueing to race with a thread that is
going to sleep. To address that, we queue the xprt and then search again.
If we find an idle thread at that point, we can't attach the xprt to it
directly since that might race with a different thread waking up and
finding it. All we can do is wake the idle thread back up and let it
attempt to find the now-queued xprt.
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Tested-by: Chris Worley <chris.worley@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
In a later patch, we'll be removing some spinlocking around the socket
and thread queueing code in order to fix some contention problems. At
that point, the stats counters will no longer be protected by the
sp_lock.
Change the counters to atomic_long_t fields, except for the
"sockets_queued" counter which will still be manipulated under a
spinlock.
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Tested-by: Chris Worley <chris.worley@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
In a later patch, we'll want to be able to handle this flag without
holding the sp_lock. Change this field to an unsigned long flags
field, and declare a new flag in it that can be managed with atomic
bitops.
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
There are a couple of holes in the svc_rqst field on x86_64. Move the
rq_cachetype to a different location to eliminate both of them.
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
In a later patch, we're going to need some atomic bit flags. Since that
field will need to be an unsigned long, we mitigate that space
consumption by migrating some other bitflags to the new field. Start
with the rq_secure flag.
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Mainly what I need is 860a0d9e51 "sunrpc: add some tracepoints in
svc_rqst handling functions", which subsequent server rpc patches from
jlayton depend on. I'm merging this later tag on the assumption that's
more likely to be a tested and stable point.
All it does is indicate whether a xprt has already been deleted from
a list or not, which is unnecessary since we use list_del_init and it's
always set and checked under the sv_lock anyway.
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Add a new directory heirarchy under the debugfs sunrpc/ directory:
sunrpc/
rpc_xprt/
<xprt id>/
Within that directory, we can put files that give info about the
xprts. We do have the (minor) problem that there is no succinct,
unique identifier for rpc_xprts. So we generate them synthetically
with a static atomic_t counter.
For now, this directory just holds an "info" file, but we may add
other files to it in the future.
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
It's possible to get a dump of the RPC task queue by writing a value to
/proc/sys/sunrpc/rpc_debug. If you write any value to that file, you get
a dump of the RPC client task list into the log buffer. This is a rather
inconvenient interface however, and makes it hard to get immediate info
about the task queue.
Add a new directory hierarchy under debugfs:
sunrpc/
rpc_clnt/
<clientid>/
Within each clientid directory we create a new "tasks" file that will
dump info similar to what shows up in the log buffer, but with a few
small differences -- we avoid printing raw kernel addresses in favor of
symbolic names and the XID is also displayed.
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Pull pull additional NFS client changes for 3.19 from Anna Schumaker:
"NFS: Generic client side changes from Chuck
These patches fixes for iostats and SETCLIENTID in addition to cleaning
up the nfs4_init_callback() function.
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>"
* tag 'nfs-cel-for-3.19' of git://git.linux-nfs.org/projects/anna/nfs-rdma:
NFS: Clean up nfs4_init_callback()
NFS: SETCLIENTID XDR buffer sizes are incorrect
SUNRPC: serialize iostats updates
Occasionally mountstats reports a negative retransmission rate.
Ensure that two RPCs completing concurrently don't confuse the sums
in the transport's op_metrics array.
Since pNFS filelayout can invoke rpc_count_iostats() on another
transport from xprt_release(), we can't rely on simply holding the
transport_lock in xprt_release(). There's nothing for it but hard
serialization. One spin lock per RPC operation should make this as
painless as it can be.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Add tracepoints inside the main loop on xs_tcp_data_recv that allow
us to keep an eye on what's happening during each phase of it.
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Pull nfsd updates from Bruce Fields:
"Highlights:
- support the NFSv4.2 SEEK operation (allowing clients to support
SEEK_HOLE/SEEK_DATA), thanks to Anna.
- end the grace period early in a number of cases, mitigating a
long-standing annoyance, thanks to Jeff
- improve SMP scalability, thanks to Trond"
* 'for-3.18' of git://linux-nfs.org/~bfields/linux: (55 commits)
nfsd: eliminate "to_delegation" define
NFSD: Implement SEEK
NFSD: Add generic v4.2 infrastructure
svcrdma: advertise the correct max payload
nfsd: introduce nfsd4_callback_ops
nfsd: split nfsd4_callback initialization and use
nfsd: introduce a generic nfsd4_cb
nfsd: remove nfsd4_callback.cb_op
nfsd: do not clear rpc_resp in nfsd4_cb_done_sequence
nfsd: fix nfsd4_cb_recall_done error handling
nfsd4: clarify how grace period ends
nfsd4: stop grace_time update at end of grace period
nfsd: skip subsequent UMH "create" operations after the first one for v4.0 clients
nfsd: set and test NFSD4_CLIENT_STABLE bit to reduce nfsdcltrack upcalls
nfsd: serialize nfsdcltrack upcalls for a particular client
nfsd: pass extra info in env vars to upcalls to allow for early grace period end
nfsd: add a v4_end_grace file to /proc/fs/nfsd
lockd: add a /proc/fs/lockd/nlm_end_grace file
nfsd: reject reclaim request when client has already sent RECLAIM_COMPLETE
nfsd: remove redundant boot_time parm from grace_done client tracking op
...
When aborting a connection to preserve source ports, don't wake the task in
xs_error_report. This allows tasks with RPC_TASK_SOFTCONN to succeed if the
connection needs to be re-established since it preserves the task's status
instead of setting it to the status of the aborting kernel_connect().
This may also avoid a potential conflict on the socket's lock.
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Cc: stable@vger.kernel.org # 3.14+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
We're always _only_ waking up tasks from within the sp_threads list, so
we know that they are enqueued and alive. The rq_wait waitqueue is just
a distraction with extra atomic semantics.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Pull NFS client updates from Trond Myklebust:
"Highlights include:
- stable fix for a bug in nfs3_list_one_acl()
- speed up NFS path walks by supporting LOOKUP_RCU
- more read/write code cleanups
- pNFS fixes for layout return on close
- fixes for the RCU handling in the rpcsec_gss code
- more NFS/RDMA fixes"
* tag 'nfs-for-3.17-1' of git://git.linux-nfs.org/projects/trondmy/linux-nfs: (79 commits)
nfs: reject changes to resvport and sharecache during remount
NFS: Avoid infinite loop when RELEASE_LOCKOWNER getting expired error
SUNRPC: remove all refcounting of groupinfo from rpcauth_lookupcred
NFS: fix two problems in lookup_revalidate in RCU-walk
NFS: allow lockless access to access_cache
NFS: teach nfs_lookup_verify_inode to handle LOOKUP_RCU
NFS: teach nfs_neg_need_reval to understand LOOKUP_RCU
NFS: support RCU_WALK in nfs_permission()
sunrpc/auth: allow lockless (rcu) lookup of credential cache.
NFS: prepare for RCU-walk support but pushing tests later in code.
NFS: nfs4_lookup_revalidate: only evaluate parent if it will be used.
NFS: add checks for returned value of try_module_get()
nfs: clear_request_commit while holding i_lock
pnfs: add pnfs_put_lseg_async
pnfs: find swapped pages on pnfs commit lists too
nfs: fix comment and add warn_on for PG_INODE_REF
nfs: check wait_on_bit_lock err in page_group_lock
sunrpc: remove "ec" argument from encrypt_v2 operation
sunrpc: clean up sparse endianness warnings in gss_krb5_wrap.c
sunrpc: clean up sparse endianness warnings in gss_krb5_seal.c
...
Pull nfsd updates from Bruce Fields:
"This includes a major rewrite of the NFSv4 state code, which has
always depended on a single mutex. As an example, open creates are no
longer serialized, fixing a performance regression on NFSv3->NFSv4
upgrades. Thanks to Jeff, Trond, and Benny, and to Christoph for
review.
Also some RDMA fixes from Chuck Lever and Steve Wise, and
miscellaneous fixes from Kinglong Mee and others"
* 'for-3.17' of git://linux-nfs.org/~bfields/linux: (167 commits)
svcrdma: remove rdma_create_qp() failure recovery logic
nfsd: add some comments to the nfsd4 object definitions
nfsd: remove the client_mutex and the nfs4_lock/unlock_state wrappers
nfsd: remove nfs4_lock_state: nfs4_state_shutdown_net
nfsd: remove nfs4_lock_state: nfs4_laundromat
nfsd: Remove nfs4_lock_state(): reclaim_complete()
nfsd: Remove nfs4_lock_state(): setclientid, setclientid_confirm, renew
nfsd: Remove nfs4_lock_state(): exchange_id, create/destroy_session()
nfsd: Remove nfs4_lock_state(): nfsd4_open and nfsd4_open_confirm
nfsd: Remove nfs4_lock_state(): nfsd4_delegreturn()
nfsd: Remove nfs4_lock_state(): nfsd4_open_downgrade + nfsd4_close
nfsd: Remove nfs4_lock_state(): nfsd4_lock/locku/lockt()
nfsd: Remove nfs4_lock_state(): nfsd4_release_lockowner
nfsd: Remove nfs4_lock_state(): nfsd4_test_stateid/nfsd4_free_stateid
nfsd: Remove nfs4_lock_state(): nfs4_preprocess_stateid_op()
nfsd: remove old fault injection infrastructure
nfsd: add more granular locking to *_delegations fault injectors
nfsd: add more granular locking to forget_openowners fault injector
nfsd: add more granular locking to forget_locks fault injector
nfsd: add a list_head arg to nfsd_foreach_client_lock
...
The new flag RPCAUTH_LOOKUP_RCU to credential lookup avoids locking,
does not take a reference on the returned credential, and returns
-ECHILD if a simple lookup was not possible.
The returned value can only be used within an rcu_read_lock protected
region.
The main user of this is the new rpc_lookup_cred_nonblock() which
returns a pointer to the current credential which is only rcu-safe (no
ref-count held), and might return -ECHILD if allocation was required.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
