xprtrdma: Move credit update to RPC reply handler
Reduce work in the receive CQ handler, which can be run at hardware
interrupt level, by moving the RPC/RDMA credit update logic to the
RPC reply handler.
This has some additional benefits: More header sanity checking is
done before trusting the incoming credit value, and the receive CQ
handler no longer touches the RPC/RDMA header (the CPU stalls while
waiting for the header contents to be brought into the cache).
This further extends work begun by commit e7ce710a8802 ("xprtrdma:
Avoid deadlock when credit window is reset").
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 1000f63..71a071a 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -49,6 +49,7 @@
#include <linux/interrupt.h>
#include <linux/slab.h>
+#include <linux/prefetch.h>
#include <asm/bitops.h>
#include "xprt_rdma.h"
@@ -298,17 +299,7 @@
rep->rr_len = wc->byte_len;
ib_dma_sync_single_for_cpu(rdmab_to_ia(rep->rr_buffer)->ri_id->device,
rep->rr_iov.addr, rep->rr_len, DMA_FROM_DEVICE);
-
- if (rep->rr_len >= 16) {
- struct rpcrdma_msg *p = (struct rpcrdma_msg *)rep->rr_base;
- unsigned int credits = ntohl(p->rm_credit);
-
- if (credits == 0)
- credits = 1; /* don't deadlock */
- else if (credits > rep->rr_buffer->rb_max_requests)
- credits = rep->rr_buffer->rb_max_requests;
- atomic_set(&rep->rr_buffer->rb_credits, credits);
- }
+ prefetch(rep->rr_base);
out_schedule:
list_add_tail(&rep->rr_list, sched_list);
@@ -480,7 +471,6 @@
case RDMA_CM_EVENT_DEVICE_REMOVAL:
connstate = -ENODEV;
connected:
- atomic_set(&rpcx_to_rdmax(ep->rep_xprt)->rx_buf.rb_credits, 1);
dprintk("RPC: %s: %sconnected\n",
__func__, connstate > 0 ? "" : "dis");
ep->rep_connected = connstate;
@@ -1186,7 +1176,6 @@
buf->rb_max_requests = cdata->max_requests;
spin_lock_init(&buf->rb_lock);
- atomic_set(&buf->rb_credits, 1);
/* Need to allocate:
* 1. arrays for send and recv pointers