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Date: Thu, 25 Jun 2015 16:02:04 +0530
From: Govindarajulu Varadarajan <_govind@....com>
To: davem@...emloft.net, netdev@...r.kernel.org
Cc: ssujith@...co.com, benve@...co.com,
Govindarajulu Varadarajan <_govind@....com>
Subject: [PATCH net-next v2] enic: use atomic_t instead of spin_lock in busy poll
We use spinlock to access a single flag. We can avoid spin_locks by using
atomic variable and atomic_cmpxchg(). Use atomic_cmpxchg to set the flag
for idle to poll. And a simple atomic_set to unlock (set idle from poll).
In napi poll, if gro is enabled, we call napi_gro_receive() to deliver the
packets. Before we call napi_complete(), i.e while re-polling, if low
latency busy poll is called, we use netif_receive_skb() to deliver the packets.
At this point if there are some skb's held in GRO, busy poll could deliver the
packets out of order. So we call napi_gro_flush() to flush skbs before we
move the napi poll to idle.
Signed-off-by: Govindarajulu Varadarajan <_govind@....com>
---
v2: Add more details about why gro flush is required while unlocking napi poll.
drivers/net/ethernet/cisco/enic/enic_main.c | 4 +-
drivers/net/ethernet/cisco/enic/vnic_rq.h | 91 +++++++++--------------------
2 files changed, 29 insertions(+), 66 deletions(-)
diff --git a/drivers/net/ethernet/cisco/enic/enic_main.c b/drivers/net/ethernet/cisco/enic/enic_main.c
index eadae1b..da2004e 100644
--- a/drivers/net/ethernet/cisco/enic/enic_main.c
+++ b/drivers/net/ethernet/cisco/enic/enic_main.c
@@ -1208,7 +1208,7 @@ static int enic_poll(struct napi_struct *napi, int budget)
napi_complete(napi);
vnic_intr_unmask(&enic->intr[intr]);
}
- enic_poll_unlock_napi(&enic->rq[cq_rq]);
+ enic_poll_unlock_napi(&enic->rq[cq_rq], napi);
return rq_work_done;
}
@@ -1414,7 +1414,7 @@ static int enic_poll_msix_rq(struct napi_struct *napi, int budget)
*/
enic_calc_int_moderation(enic, &enic->rq[rq]);
- enic_poll_unlock_napi(&enic->rq[rq]);
+ enic_poll_unlock_napi(&enic->rq[rq], napi);
if (work_done < work_to_do) {
/* Some work done, but not enough to stay in polling,
diff --git a/drivers/net/ethernet/cisco/enic/vnic_rq.h b/drivers/net/ethernet/cisco/enic/vnic_rq.h
index 8111d52..b9c82f1 100644
--- a/drivers/net/ethernet/cisco/enic/vnic_rq.h
+++ b/drivers/net/ethernet/cisco/enic/vnic_rq.h
@@ -21,6 +21,7 @@
#define _VNIC_RQ_H_
#include <linux/pci.h>
+#include <linux/netdevice.h>
#include "vnic_dev.h"
#include "vnic_cq.h"
@@ -75,6 +76,12 @@ struct vnic_rq_buf {
uint64_t wr_id;
};
+enum enic_poll_state {
+ ENIC_POLL_STATE_IDLE,
+ ENIC_POLL_STATE_NAPI,
+ ENIC_POLL_STATE_POLL
+};
+
struct vnic_rq {
unsigned int index;
struct vnic_dev *vdev;
@@ -86,19 +93,7 @@ struct vnic_rq {
void *os_buf_head;
unsigned int pkts_outstanding;
#ifdef CONFIG_NET_RX_BUSY_POLL
-#define ENIC_POLL_STATE_IDLE 0
-#define ENIC_POLL_STATE_NAPI (1 << 0) /* NAPI owns this poll */
-#define ENIC_POLL_STATE_POLL (1 << 1) /* poll owns this poll */
-#define ENIC_POLL_STATE_NAPI_YIELD (1 << 2) /* NAPI yielded this poll */
-#define ENIC_POLL_STATE_POLL_YIELD (1 << 3) /* poll yielded this poll */
-#define ENIC_POLL_YIELD (ENIC_POLL_STATE_NAPI_YIELD | \
- ENIC_POLL_STATE_POLL_YIELD)
-#define ENIC_POLL_LOCKED (ENIC_POLL_STATE_NAPI | \
- ENIC_POLL_STATE_POLL)
-#define ENIC_POLL_USER_PEND (ENIC_POLL_STATE_POLL | \
- ENIC_POLL_STATE_POLL_YIELD)
- unsigned int bpoll_state;
- spinlock_t bpoll_lock;
+ atomic_t bpoll_state;
#endif /* CONFIG_NET_RX_BUSY_POLL */
};
@@ -215,76 +210,43 @@ static inline int vnic_rq_fill(struct vnic_rq *rq,
#ifdef CONFIG_NET_RX_BUSY_POLL
static inline void enic_busy_poll_init_lock(struct vnic_rq *rq)
{
- spin_lock_init(&rq->bpoll_lock);
- rq->bpoll_state = ENIC_POLL_STATE_IDLE;
+ atomic_set(&rq->bpoll_state, ENIC_POLL_STATE_IDLE);
}
static inline bool enic_poll_lock_napi(struct vnic_rq *rq)
{
- bool rc = true;
-
- spin_lock(&rq->bpoll_lock);
- if (rq->bpoll_state & ENIC_POLL_LOCKED) {
- WARN_ON(rq->bpoll_state & ENIC_POLL_STATE_NAPI);
- rq->bpoll_state |= ENIC_POLL_STATE_NAPI_YIELD;
- rc = false;
- } else {
- rq->bpoll_state = ENIC_POLL_STATE_NAPI;
- }
- spin_unlock(&rq->bpoll_lock);
+ int rc = atomic_cmpxchg(&rq->bpoll_state, ENIC_POLL_STATE_IDLE,
+ ENIC_POLL_STATE_NAPI);
- return rc;
+ return (rc == ENIC_POLL_STATE_IDLE);
}
-static inline bool enic_poll_unlock_napi(struct vnic_rq *rq)
+static inline void enic_poll_unlock_napi(struct vnic_rq *rq,
+ struct napi_struct *napi)
{
- bool rc = false;
-
- spin_lock(&rq->bpoll_lock);
- WARN_ON(rq->bpoll_state &
- (ENIC_POLL_STATE_POLL | ENIC_POLL_STATE_NAPI_YIELD));
- if (rq->bpoll_state & ENIC_POLL_STATE_POLL_YIELD)
- rc = true;
- rq->bpoll_state = ENIC_POLL_STATE_IDLE;
- spin_unlock(&rq->bpoll_lock);
-
- return rc;
+ WARN_ON(atomic_read(&rq->bpoll_state) != ENIC_POLL_STATE_NAPI);
+ napi_gro_flush(napi, false);
+ atomic_set(&rq->bpoll_state, ENIC_POLL_STATE_IDLE);
}
static inline bool enic_poll_lock_poll(struct vnic_rq *rq)
{
- bool rc = true;
-
- spin_lock_bh(&rq->bpoll_lock);
- if (rq->bpoll_state & ENIC_POLL_LOCKED) {
- rq->bpoll_state |= ENIC_POLL_STATE_POLL_YIELD;
- rc = false;
- } else {
- rq->bpoll_state |= ENIC_POLL_STATE_POLL;
- }
- spin_unlock_bh(&rq->bpoll_lock);
+ int rc = atomic_cmpxchg(&rq->bpoll_state, ENIC_POLL_STATE_IDLE,
+ ENIC_POLL_STATE_POLL);
- return rc;
+ return (rc == ENIC_POLL_STATE_IDLE);
}
-static inline bool enic_poll_unlock_poll(struct vnic_rq *rq)
-{
- bool rc = false;
- spin_lock_bh(&rq->bpoll_lock);
- WARN_ON(rq->bpoll_state & ENIC_POLL_STATE_NAPI);
- if (rq->bpoll_state & ENIC_POLL_STATE_POLL_YIELD)
- rc = true;
- rq->bpoll_state = ENIC_POLL_STATE_IDLE;
- spin_unlock_bh(&rq->bpoll_lock);
-
- return rc;
+static inline void enic_poll_unlock_poll(struct vnic_rq *rq)
+{
+ WARN_ON(atomic_read(&rq->bpoll_state) != ENIC_POLL_STATE_POLL);
+ atomic_set(&rq->bpoll_state, ENIC_POLL_STATE_IDLE);
}
static inline bool enic_poll_busy_polling(struct vnic_rq *rq)
{
- WARN_ON(!(rq->bpoll_state & ENIC_POLL_LOCKED));
- return rq->bpoll_state & ENIC_POLL_USER_PEND;
+ return atomic_read(&rq->bpoll_state) & ENIC_POLL_STATE_POLL;
}
#else
@@ -298,7 +260,8 @@ static inline bool enic_poll_lock_napi(struct vnic_rq *rq)
return true;
}
-static inline bool enic_poll_unlock_napi(struct vnic_rq *rq)
+static inline bool enic_poll_unlock_napi(struct vnic_rq *rq,
+ struct napi_struct *napi)
{
return false;
}
--
2.4.4
--
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