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xprtrdma: Use an llist to manage free rpcrdma_reps

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rpcrdma_rep objects are removed from their free list by only a
single thread: the Receive completion handler. Thus that free list
can be converted to an llist, where a single-threaded consumer and
a multi-threaded producer (rpcrdma_buffer_put) can both access the
llist without the need for any serialization.

This eliminates spin lock contention between the Receive completion
handler and rpcrdma_buffer_get, and makes the rep consumer wait-
free.

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
2019-08-19 18:48:43 -04:00
committed by Anna Schumaker
parent 4d6b8890dd
commit b0b227f071
2 changed files with 53 additions and 59 deletions
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6
net/sunrpc/xprtrdma/xprt_rdma.h
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@@ -47,6 +47,7 @@
#include <linux/atomic.h> /* atomic_t, etc */
#include <linux/kref.h> /* struct kref */
#include <linux/workqueue.h> /* struct work_struct */
#include <linux/llist.h>
#include <rdma/rdma_cm.h> /* RDMA connection api */
#include <rdma/ib_verbs.h> /* RDMA verbs api */
@@ -200,7 +201,7 @@ struct rpcrdma_rep {
struct rpc_rqst *rr_rqst;
struct xdr_buf rr_hdrbuf;
struct xdr_stream rr_stream;
struct list_head rr_list;
struct llist_node rr_node;
struct ib_recv_wr rr_recv_wr;
};
@@ -362,7 +363,6 @@ rpcrdma_mr_pop(struct list_head *list)
struct rpcrdma_buffer {
spinlock_t rb_lock;
struct list_head rb_send_bufs;
struct list_head rb_recv_bufs;
struct list_head rb_mrs;
unsigned long rb_sc_head;
@@ -373,6 +373,8 @@ struct rpcrdma_buffer {
struct list_head rb_allreqs;
struct list_head rb_all_mrs;
struct llist_head rb_free_reps;
u32 rb_max_requests;
u32 rb_credits; /* most recent credit grant */