On 18.03.2016 13:27, Xie, Huawei wrote:

On 3/18/2016 6:23 PM, Ilya Maximets wrote:

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On 18.03.2016 13:08, Xie, Huawei wrote:

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On 2/24/2016 7:47 PM, Ilya Maximets wrote:

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 		 * Wait until it's our turn to add our buffer

@@ -979,7 +979,7 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
 		entry_success++;
 	}
 
-	rte_compiler_barrier();
+	rte_smp_rmb();

smp_rmb()?

There is no such function 'smp_rmb' in DPDK.
But:
.../arch/arm/rte_atomic.h:#define rte_smp_rmb() rte_rmb()
.../arch/ppc_64/rte_atomic.h:#define rte_smp_rmb() rte_compiler_barrier()
.../arch/tile/rte_atomic.h:#define rte_smp_rmb() rte_compiler_barrier()
.../arch/x86/rte_atomic.h:#define rte_smp_rmb() rte_compiler_barrier()

I mean shoudn't be rte_smp_wmb()?

No. Here we need to be sure that copying of data from descriptor to
our local mbuf completed before 'vq->used->idx += entry_success;'.

Read memory barrier will help us with it.

In other places write barriers used because copying performed in
opposite direction.

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 	vq->used->idx += entry_success;
 	vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
 			sizeof(vq->used->idx));
-- 2.5.0