xprtrdma: Limit work done by completion handler
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>
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@ -165,8 +165,9 @@ static int
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rpcrdma_sendcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
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rpcrdma_sendcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
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{
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{
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struct ib_wc *wcs;
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struct ib_wc *wcs;
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int count, rc;
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int budget, count, rc;
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budget = RPCRDMA_WC_BUDGET / RPCRDMA_POLLSIZE;
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do {
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do {
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wcs = ep->rep_send_wcs;
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wcs = ep->rep_send_wcs;
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@ -177,7 +178,7 @@ rpcrdma_sendcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
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count = rc;
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count = rc;
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while (count-- > 0)
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while (count-- > 0)
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rpcrdma_sendcq_process_wc(wcs++);
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rpcrdma_sendcq_process_wc(wcs++);
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} while (rc == RPCRDMA_POLLSIZE);
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} while (rc == RPCRDMA_POLLSIZE && --budget);
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return 0;
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return 0;
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}
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}
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@ -254,8 +255,9 @@ static int
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rpcrdma_recvcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
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rpcrdma_recvcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
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{
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{
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struct ib_wc *wcs;
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struct ib_wc *wcs;
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int count, rc;
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int budget, count, rc;
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budget = RPCRDMA_WC_BUDGET / RPCRDMA_POLLSIZE;
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do {
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do {
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wcs = ep->rep_recv_wcs;
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wcs = ep->rep_recv_wcs;
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@ -266,7 +268,7 @@ rpcrdma_recvcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
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count = rc;
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count = rc;
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while (count-- > 0)
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while (count-- > 0)
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rpcrdma_recvcq_process_wc(wcs++);
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rpcrdma_recvcq_process_wc(wcs++);
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} while (rc == RPCRDMA_POLLSIZE);
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} while (rc == RPCRDMA_POLLSIZE && --budget);
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return 0;
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return 0;
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}
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}
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@ -74,6 +74,7 @@ struct rpcrdma_ia {
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* RDMA Endpoint -- one per transport instance
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* RDMA Endpoint -- one per transport instance
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*/
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*/
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#define RPCRDMA_WC_BUDGET (128)
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#define RPCRDMA_POLLSIZE (16)
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#define RPCRDMA_POLLSIZE (16)
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struct rpcrdma_ep {
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struct rpcrdma_ep {
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