[PATCH v1 12/14] xprtrdma: Split rb_lock

Chuck Lever
2015-05-04T17:58:37Z

/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 is always in a different cacheline than rb_lock and the
buffer pointers.

Signed-off-by: Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
---
net/sunrpc/xprtrdma/fmr_ops.c | 1 +
net/sunrpc/xprtrdma/frwr_ops.c | 1 +
net/sunrpc/xprtrdma/verbs.c | 10 ++++------
net/sunrpc/xprtrdma/xprt_rdma.h | 16 +++++++++-------
4 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/net/sunrpc/xprtrdma/fmr_ops.c b/net/sunrpc/xprtrdma/fmr_ops.c
index 5dd77da..52f9ad5 100644
--- 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 3fb609a..edc10ba 100644
--- 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 1f51547..c5830cd 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1179,15 +1179,14 @@ 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__);
@@ -1198,11 +1197,10 @@ 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 5650c23..ae31fc7 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -283,15 +283,17 @@ 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)