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xprtrdma: Limit work done by completion handler

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Sagi Grimberg <sagig@dev.mellanox.co.il> points out that a steady
stream of CQ events could starve other work because of the boundless
loop pooling in rpcrdma_{send,recv}_poll().

Instead of a (potentially infinite) while loop, return after
collecting a budgeted number of completions.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Acked-by: Sagi Grimberg <sagig@dev.mellanox.co.il>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Chuck Lever 2014-05-28 10:33:51 -04:00 committed by Anna Schumaker
parent 1c00dd0776
commit 8301a2c047
2 changed files with 7 additions and 4 deletions
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10
net/sunrpc/xprtrdma/verbs.c
View File

@ -165,8 +165,9 @@ static int
rpcrdma_sendcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
{
struct ib_wc *wcs;
int count, rc;
int budget, count, rc;
budget = RPCRDMA_WC_BUDGET / RPCRDMA_POLLSIZE;
do {
wcs = ep->rep_send_wcs;
@ -177,7 +178,7 @@ rpcrdma_sendcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
count = rc;
while (count-- > 0)
rpcrdma_sendcq_process_wc(wcs++);
} while (rc == RPCRDMA_POLLSIZE);
} while (rc == RPCRDMA_POLLSIZE && --budget);
return 0;
}
@ -254,8 +255,9 @@ static int
rpcrdma_recvcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
{
struct ib_wc *wcs;
int count, rc;
int budget, count, rc;
budget = RPCRDMA_WC_BUDGET / RPCRDMA_POLLSIZE;
do {
wcs = ep->rep_recv_wcs;
@ -266,7 +268,7 @@ rpcrdma_recvcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
count = rc;
while (count-- > 0)
rpcrdma_recvcq_process_wc(wcs++);
} while (rc == RPCRDMA_POLLSIZE);
} while (rc == RPCRDMA_POLLSIZE && --budget);
return 0;
}

1
net/sunrpc/xprtrdma/xprt_rdma.h
View File

@ -74,6 +74,7 @@ struct rpcrdma_ia {
* RDMA Endpoint -- one per transport instance
*/
#define RPCRDMA_WC_BUDGET (128)
#define RPCRDMA_POLLSIZE (16)
struct rpcrdma_ep {