[PATCH 4/5] vhost: do not use rte_memcpy for virtio_hdr copy
From: Yuanhan Liu <hidden>
Date: 2015-12-03 06:02:48
Subsystem:
library code, the rest · Maintainers:
Andrew Morton, Linus Torvalds
First of all, rte_memcpy() is mostly useful for coping big packets
by leveraging hardware advanced instructions like AVX. But for virtio
net hdr, which is 12 bytes at most, invoking rte_memcpy() will not
introduce any performance boost.
And, to my suprise, rte_memcpy() is huge. Since rte_memcpy() is
inlined, it takes more space every time we call it at a different
place. Replacing the two rte_memcpy() with directly copy saves
nearly 12K bytes of code size!
# without this patch
$ size /path/to/vhost_rxtx.o
text data bss dec hex filename
36171 0 0 36171 8d4b /path/to/vhost_rxtx.o
# with this patch
$ size /path/to/vhost_rxtx.o
text data bss dec hex filename
24179 0 0 24179 5e73 /path/to/vhost_rxtx.o
Signed-off-by: Yuanhan Liu <redacted>
---
lib/librte_vhost/vhost_rxtx.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index 7464b6b..1e0a24e 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c@@ -70,14 +70,17 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq, 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_mrg_rxbuf hdr = {{0, 0, 0, 0, 0, 0}, 0}; desc = &vq->desc[desc_idx]; desc_addr = gpa_to_vva(dev, desc->addr); rte_prefetch0((void *)(uintptr_t)desc_addr); - rte_memcpy((void *)(uintptr_t)desc_addr, - (const void *)&virtio_hdr, vq->vhost_hlen); + if (vq->vhost_hlen == sizeof(struct virtio_net_hdr_mrg_rxbuf)) { + *(struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)desc_addr = hdr; + } else { + *(struct virtio_net_hdr *)(uintptr_t)desc_addr = hdr.hdr; + } PRINT_PACKET(dev, (uintptr_t)desc_addr, vq->vhost_hlen, 0); desc_offset = vq->vhost_hlen;
@@ -340,7 +343,7 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq, uint16_t res_start_idx, uint16_t res_end_idx, struct rte_mbuf *pkt) { - struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0}; + struct virtio_net_hdr_mrg_rxbuf hdr = {{0, 0, 0, 0, 0, 0}, 0}; uint32_t vec_idx = 0; uint16_t cur_idx = res_start_idx; uint64_t desc_addr;
@@ -361,13 +364,16 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq, rte_prefetch0((void *)(uintptr_t)desc_addr); - virtio_hdr.num_buffers = res_end_idx - res_start_idx; + hdr.num_buffers = res_end_idx - res_start_idx; LOG_DEBUG(VHOST_DATA, "(%"PRIu64") RX: Num merge buffers %d\n", dev->device_fh, virtio_hdr.num_buffers); - rte_memcpy((void *)(uintptr_t)desc_addr, - (const void *)&virtio_hdr, vq->vhost_hlen); + if (vq->vhost_hlen == sizeof(struct virtio_net_hdr_mrg_rxbuf)) { + *(struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)desc_addr = hdr; + } else { + *(struct virtio_net_hdr *)(uintptr_t)desc_addr = hdr.hdr; + } PRINT_PACKET(dev, (uintptr_t)desc_addr, vq->vhost_hlen, 0); desc_avail = vq->buf_vec[vec_idx].buf_len - vq->vhost_hlen;
--
1.9.0