[dpdk-dev] [memnic PATCH] pmd: use rte_atomic32_cmpset instead of cmpxchg

[Olivier MATZ]

On Thursday, April 03, 2014 07:34:56 AM Hiroshi Shimamoto wrote:
> From: Hiroshi Shimamoto 
> 
> Because DPDK has its own compare and set function to optimize to
> dedicated processor type, use that rte_atomic32_cmpset() instead of
> cmpxchg macro which is specially introduced for MEMNIC.
> 
> Signed-off-by: Hiroshi Shimamoto 
> ---
>  common/memnic.h  | 12 
>  pmd/pmd_memnic.c | 10 ++
>  2 files changed, 6 insertions(+), 16 deletions(-)

Reviewed-by: Olivier Matz 

[dpdk-dev] [memnic PATCH] pmd: use rte_atomic32_cmpset instead of cmpxchg

[Hiroshi Shimamoto]

From: Hiroshi Shimamoto 

Because DPDK has its own compare and set function to optimize to
dedicated processor type, use that rte_atomic32_cmpset() instead of
cmpxchg macro which is specially introduced for MEMNIC.

Signed-off-by: Hiroshi Shimamoto 
---
 common/memnic.h  | 12 
 pmd/pmd_memnic.c | 10 ++
 2 files changed, 6 insertions(+), 16 deletions(-)

diff --git a/common/memnic.h b/common/memnic.h
index 2187ac1..84e941c 100644
--- a/common/memnic.h
+++ b/common/memnic.h
@@ -120,18 +120,6 @@ struct memnic_area {
 /* for userspace */
 #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))

-static inline uint32_t cmpxchg(uint32_t *dst, uint32_t old, uint32_t new)
-{
-   volatile uint32_t *ptr = (volatile uint32_t *)dst;
-   uint32_t ret;
-
-   asm volatile("lock; cmpxchgl %2, %1"
-: "=a" (ret), "+m" (*ptr)
-: "r" (new), "0" (old)
-: "memory");
-
-   return ret;
-}
 #endif /* __KERNEL__ */

 #endif /* MEMNIC_H */
diff --git a/pmd/pmd_memnic.c b/pmd/pmd_memnic.c
index 4a1c1e4..4abdf26 100644
--- a/pmd/pmd_memnic.c
+++ b/pmd/pmd_memnic.c
@@ -314,7 +314,7 @@ static uint16_t memnic_xmit_pkts(void *tx_queue,
struct memnic_data *data = >nic->down;
struct memnic_packet *p;
uint16_t nr;
-   int idx, old;
+   int idx;
struct rte_eth_stats *st = >stats[rte_lcore_id()];
uint64_t pkts, bytes, errs;

@@ -335,10 +335,12 @@ static uint16_t memnic_xmit_pkts(void *tx_queue,
 retry:
idx = ACCESS_ONCE(adapter->down_idx);
p = >packets[idx];
-   old = cmpxchg(>status, MEMNIC_PKT_ST_FREE, 
MEMNIC_PKT_ST_USED);
-   if (old != MEMNIC_PKT_ST_FREE) {
-   if (old == MEMNIC_PKT_ST_FILLED &&
+   if (unlikely(rte_atomic32_cmpset(>status,
+   MEMNIC_PKT_ST_FREE, MEMNIC_PKT_ST_USED) == 0)) {
+   /* cmpxchg failed */
+   if (p->status == MEMNIC_PKT_ST_FILLED &&
idx == ACCESS_ONCE(adapter->down_idx)) {
+   /* what we're seeing is FILLED means queue full 
*/
errs++;
break;
}
-- 
1.8.4