Commit e7104a2a authored by Chuck Lever's avatar Chuck Lever Committed by Anna Schumaker

xprtrdma: Cap req_cqinit

Recent work made FRMR registration and invalidation completions
unsignaled. This greatly reduces the adapter interrupt rate.

Every so often, however, a posted send Work Request is allowed to
signal. Otherwise, the provider's Work Queue will wrap and the
workload will hang.

The number of Work Requests that are allowed to remain unsignaled is
determined by the value of req_cqinit. Currently, this is set to the
size of the send Work Queue divided by two, minus 1.

For FRMR, the send Work Queue is the maximum number of concurrent
RPCs (currently 32) times the maximum number of Work Requests an
RPC might use (currently 7, though some adapters may need more).

For mlx4, this is 224 entries. This leaves completion signaling
disabled for 111 send Work Requests.

Some providers hold back dispatching Work Requests until a CQE is
generated.  If completions are disabled, then no CQEs are generated
for quite some time, and that can stall the Work Queue.

I've seen this occur running xfstests generic/113 over NFSv4, where
eventually, posting a FAST_REG_MR Work Request fails with -ENOMEM
because the Work Queue has overflowed. The connection is dropped
and re-established.

Cap the rep_cqinit setting so completions are not left turned off
for too long.

BugLink: https://bugzilla.linux-nfs.org/show_bug.cgi?id=269Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent 92b98361
...@@ -733,7 +733,9 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia, ...@@ -733,7 +733,9 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia,
/* set trigger for requesting send completion */ /* set trigger for requesting send completion */
ep->rep_cqinit = ep->rep_attr.cap.max_send_wr/2 - 1; ep->rep_cqinit = ep->rep_attr.cap.max_send_wr/2 - 1;
if (ep->rep_cqinit <= 2) if (ep->rep_cqinit > RPCRDMA_MAX_UNSIGNALED_SENDS)
ep->rep_cqinit = RPCRDMA_MAX_UNSIGNALED_SENDS;
else if (ep->rep_cqinit <= 2)
ep->rep_cqinit = 0; ep->rep_cqinit = 0;
INIT_CQCOUNT(ep); INIT_CQCOUNT(ep);
ep->rep_ia = ia; ep->rep_ia = ia;
......
...@@ -97,6 +97,12 @@ struct rpcrdma_ep { ...@@ -97,6 +97,12 @@ struct rpcrdma_ep {
struct ib_wc rep_recv_wcs[RPCRDMA_POLLSIZE]; struct ib_wc rep_recv_wcs[RPCRDMA_POLLSIZE];
}; };
/*
* Force a signaled SEND Work Request every so often,
* in case the provider needs to do some housekeeping.
*/
#define RPCRDMA_MAX_UNSIGNALED_SENDS (32)
#define INIT_CQCOUNT(ep) atomic_set(&(ep)->rep_cqcount, (ep)->rep_cqinit) #define INIT_CQCOUNT(ep) atomic_set(&(ep)->rep_cqcount, (ep)->rep_cqinit)
#define DECR_CQCOUNT(ep) atomic_sub_return(1, &(ep)->rep_cqcount) #define DECR_CQCOUNT(ep) atomic_sub_return(1, &(ep)->rep_cqcount)
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment