xprtrdma: Split rb_lock

/proc/lock_stat showed contention between rpcrdma_buffer_get/put
and the MR allocation functions during I/O intensive workloads.

Now that MRs are no longer allocated in rpcrdma_buffer_get(),
there's no reason the rb_mws list has to be managed using the
same lock as the send/receive buffers. Split that lock. The
new lock does not need to disable interrupts because buffer
get/put is never called in an interrupt context.

struct rpcrdma_buffer is re-arranged to ensure rb_mwlock and rb_mws
are always in a different cacheline than rb_lock and the buffer
pointers.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Tested-By: Devesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/net/sunrpc/xprtrdma/fmr_ops.c b/net/sunrpc/xprtrdma/fmr_ops.c
index 5dd77da..52f9ad5 100644 (file)
--- a/net/sunrpc/xprtrdma/fmr_ops.c
+++ b/net/sunrpc/xprtrdma/fmr_ops.c
@@ -65,6 +65,7 @@ fmr_op_init(struct rpcrdma_xprt *r_xprt)
        struct rpcrdma_mw *r;
        int i, rc;
 
+       spin_lock_init(&buf->rb_mwlock);
        INIT_LIST_HEAD(&buf->rb_mws);
        INIT_LIST_HEAD(&buf->rb_all);
 

diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index 8622792..18b7305 100644 (file)
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -266,6 +266,7 @@ frwr_op_init(struct rpcrdma_xprt *r_xprt)
        struct ib_pd *pd = r_xprt->rx_ia.ri_pd;
        int i;
 
+       spin_lock_init(&buf->rb_mwlock);
        INIT_LIST_HEAD(&buf->rb_mws);
        INIT_LIST_HEAD(&buf->rb_all);
 

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index cc1a526..2340835 100644 (file)
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1173,15 +1173,14 @@ rpcrdma_get_mw(struct rpcrdma_xprt *r_xprt)
 {
        struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
        struct rpcrdma_mw *mw = NULL;
-       unsigned long flags;
 
-       spin_lock_irqsave(&buf->rb_lock, flags);
+       spin_lock(&buf->rb_mwlock);
        if (!list_empty(&buf->rb_mws)) {
                mw = list_first_entry(&buf->rb_mws,
                                      struct rpcrdma_mw, mw_list);
                list_del_init(&mw->mw_list);
        }
-       spin_unlock_irqrestore(&buf->rb_lock, flags);
+       spin_unlock(&buf->rb_mwlock);
 
        if (!mw)
                pr_err("RPC:       %s: no MWs available\n", __func__);
@@ -1192,11 +1191,10 @@ void
 rpcrdma_put_mw(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mw *mw)
 {
        struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
-       unsigned long flags;
 
-       spin_lock_irqsave(&buf->rb_lock, flags);
+       spin_lock(&buf->rb_mwlock);
        list_add_tail(&mw->mw_list, &buf->rb_mws);
-       spin_unlock_irqrestore(&buf->rb_lock, flags);
+       spin_unlock(&buf->rb_mwlock);
 }
 
 static void

diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index 3ecee38..df92884 100644 (file)
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -282,15 +282,17 @@ rpcr_to_rdmar(struct rpc_rqst *rqst)
  * One of these is associated with a transport instance
  */
 struct rpcrdma_buffer {
-       spinlock_t      rb_lock;        /* protects indexes */
-       u32             rb_max_requests;/* client max requests */
-       struct list_head rb_mws;        /* optional memory windows/fmrs/frmrs */
-       struct list_head rb_all;
-       int             rb_send_index;
+       spinlock_t              rb_mwlock;      /* protect rb_mws list */
+       struct list_head        rb_mws;
+       struct list_head        rb_all;
+       char                    *rb_pool;
+
+       spinlock_t              rb_lock;        /* protect buf arrays */
+       u32                     rb_max_requests;
+       int                     rb_send_index;
+       int                     rb_recv_index;
        struct rpcrdma_req      **rb_send_bufs;
-       int             rb_recv_index;
        struct rpcrdma_rep      **rb_recv_bufs;
-       char            *rb_pool;
 };
 #define rdmab_to_ia(b) (&container_of((b), struct rpcrdma_xprt, rx_buf)->rx_ia)