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xprtrdma: Reduce the doorbell rate (Receive) 

Post RECV WRs in batches to reduce the hardware doorbell rate per
transport. This helps the RPC-over-RDMA client scale better in
number of transports.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Chuck Lever 2019-02-11 11:23:54 -05:00 committed by Anna Schumaker
parent d4550bbee6
commit e340c2d6ef
2 changed files with 12 additions and 0 deletions
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2
net/sunrpc/xprtrdma/verbs.c
View File

@ -1480,6 +1480,8 @@ rpcrdma_post_recvs(struct rpcrdma_xprt *r_xprt, bool temp)
if (ep->rep_receive_count > needed)
goto out;
needed -= ep->rep_receive_count;
if (!temp)
needed += RPCRDMA_MAX_RECV_BATCH;
count = 0;
wr = NULL;

10
net/sunrpc/xprtrdma/xprt_rdma.h
View File

@ -205,6 +205,16 @@ struct rpcrdma_rep {
struct ib_recv_wr rr_recv_wr;
};
/* To reduce the rate at which a transport invokes ib_post_recv
* (and thus the hardware doorbell rate), xprtrdma posts Receive
* WRs in batches.
*
* Setting this to zero disables Receive post batching.
*/
enum {
RPCRDMA_MAX_RECV_BATCH = 7,
};
/* struct rpcrdma_sendctx - DMA mapped SGEs to unmap after Send completes
*/
struct rpcrdma_req;