[dpdk-dev] [PATCH 4/4] lib/librte_vhost: improve vhost perf using rte_memset

[Zhiyong Yang <zhiyong.yang@intel.com>]

Using rte_memset instead of copy_virtio_net_hdr can bring 3%~4%
performance improvements on IA platform from virtio/vhost
non-mergeable loopback testing.

Two key points have been considered:
1. One variable initialization could be saved, which involves memory
store.
2. copy_virtio_net_hdr involves both load (from stack, the virtio_hdr
var) and store (to virtio driver memory), while rte_memset just involves
store.

Signed-off-by: Zhiyong Yang <zhiyong.yang@intel.com>
---
 doc/guides/rel_notes/release_17_02.rst | 11 +++++++++++
 lib/librte_vhost/virtio_net.c          | 18 +++++++++++-------
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/doc/guides/rel_notes/release_17_02.rst b/doc/guides/rel_notes/release_17_02.rst
index 3b65038..eecf857 100644
--- a/doc/guides/rel_notes/release_17_02.rst
+++ b/doc/guides/rel_notes/release_17_02.rst
@@ -38,6 +38,17 @@ New Features
      Also, make sure to start the actual text at the margin.
      =========================================================
 
+* **Introduced rte_memset and related test on IA platform.**
+
+  Performance drop had been caused in some cases on Ivybridge when DPDK code calls glibc
+  function memset. It was necessary to introduce more high efficient function to fix it.
+  The function rte_memset supported three types of instruction sets including sse & avx(128 bits),
+  avx2(256 bits) and avx512(512bits).
+
+  * Added rte_memset support on IA platform.
+  * Added functional autotest support for rte_memset.
+  * Added performance autotest support for rte_memset.
+  * Improved performance to use rte_memset instead of copy_virtio_net_hdr in lib/librte_vhost.
 
 Resolved Issues
 ---------------
diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 595f67c..392b31b 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -37,6 +37,7 @@
 
 #include <rte_mbuf.h>
 #include <rte_memcpy.h>
+#include <rte_memset.h>
 #include <rte_ether.h>
 #include <rte_ip.h>
 #include <rte_virtio_net.h>
@@ -194,7 +195,7 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vring_desc *descs,
 	uint32_t cpy_len;
 	struct vring_desc *desc;
 	uint64_t desc_addr;
-	struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0};
+	struct virtio_net_hdr *virtio_hdr;
 
 	desc = &descs[desc_idx];
 	desc_addr = gpa_to_vva(dev, desc->addr);
@@ -208,8 +209,9 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vring_desc *descs,
 
 	rte_prefetch0((void *)(uintptr_t)desc_addr);
 
-	virtio_enqueue_offload(m, &virtio_hdr.hdr);
-	copy_virtio_net_hdr(dev, desc_addr, virtio_hdr);
+	virtio_hdr = (struct virtio_net_hdr *)(uintptr_t)desc_addr;
+	rte_memset(virtio_hdr, 0, sizeof(*virtio_hdr));
+	virtio_enqueue_offload(m, virtio_hdr);
 	vhost_log_write(dev, desc->addr, dev->vhost_hlen);
 	PRINT_PACKET(dev, (uintptr_t)desc_addr, dev->vhost_hlen, 0);
 
@@ -459,7 +461,6 @@ static inline int __attribute__((always_inline))
 copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct rte_mbuf *m,
 			    struct buf_vector *buf_vec, uint16_t num_buffers)
 {
-	struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0};
 	uint32_t vec_idx = 0;
 	uint64_t desc_addr;
 	uint32_t mbuf_offset, mbuf_avail;
@@ -480,7 +481,6 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct rte_mbuf *m,
 	hdr_phys_addr = buf_vec[vec_idx].buf_addr;
 	rte_prefetch0((void *)(uintptr_t)hdr_addr);
 
-	virtio_hdr.num_buffers = num_buffers;
 	LOG_DEBUG(VHOST_DATA, "(%d) RX: num merge buffers %d\n",
 		dev->vid, num_buffers);
 
@@ -512,8 +512,12 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct rte_mbuf *m,
 		}
 
 		if (hdr_addr) {
-			virtio_enqueue_offload(hdr_mbuf, &virtio_hdr.hdr);
-			copy_virtio_net_hdr(dev, hdr_addr, virtio_hdr);
+			struct virtio_net_hdr_mrg_rxbuf *hdr =
+			(struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)hdr_addr;
+
+			rte_memset(&(hdr->hdr), 0, sizeof(hdr->hdr));
+			hdr->num_buffers = num_buffers;
+			virtio_enqueue_offload(hdr_mbuf, &(hdr->hdr));
 			vhost_log_write(dev, hdr_phys_addr, dev->vhost_hlen);
 			PRINT_PACKET(dev, (uintptr_t)hdr_addr,
 				     dev->vhost_hlen, 0);
-- 
2.7.4