| Message ID | 20210407054949.98211-1-xuanzhuo@linux.alibaba.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next] virtio-net: page_to_skb() use build_skb when there's sufficient tailroom | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for net-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | success | CCed 6 of 6 maintainers |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 87 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
On 4/7/21 7:49 AM, Xuan Zhuo wrote: > In page_to_skb(), if we have enough tailroom to save skb_shared_info, we > can use build_skb to create skb directly. No need to alloc for > additional space. And it can save a 'frags slot', which is very friendly > to GRO. > > Here, if the payload of the received package is too small (less than > GOOD_COPY_LEN), we still choose to copy it directly to the space got by > napi_alloc_skb. So we can reuse these pages. > > Testing Machine: > The four queues of the network card are bound to the cpu1. > > Test command: > for ((i=0;i<5;++i)); do sockperf tp --ip 192.168.122.64 -m 1000 -t 150& done > > The size of the udp package is 1000, so in the case of this patch, there > will always be enough tailroom to use build_skb. The sent udp packet > will be discarded because there is no port to receive it. The irqsoftd > of the machine is 100%, we observe the received quantity displayed by > sar -n DEV 1: > > no build_skb: 956864.00 rxpck/s > build_skb: 1158465.00 rxpck/s > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > Suggested-by: Jason Wang <jasowang@redhat.com> > --- This will generate merge conflicts. Please wait that commit 0f6925b3e8da ("virtio_net: Do not pull payload in skb->head") has reached net-next. Also are we sure pages are always writable, and not shared ?
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index bb4ea9dbc16b..5071a8a8f57a 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -383,17 +383,11 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, { struct sk_buff *skb; struct virtio_net_hdr_mrg_rxbuf *hdr; - unsigned int copy, hdr_len, hdr_padded_len; - char *p; + unsigned int copy, hdr_len, hdr_padded_len, tailroom, shinfo_size; + char *p, *hdr_p; p = page_address(page) + offset; - - /* copy small packet so we can reuse these pages for small data */ - skb = napi_alloc_skb(&rq->napi, GOOD_COPY_LEN); - if (unlikely(!skb)) - return NULL; - - hdr = skb_vnet_hdr(skb); + hdr_p = p; hdr_len = vi->hdr_len; if (vi->mergeable_rx_bufs) @@ -401,24 +395,33 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, else hdr_padded_len = sizeof(struct padded_vnet_hdr); - /* hdr_valid means no XDP, so we can copy the vnet header */ - if (hdr_valid) - memcpy(hdr, p, hdr_len); + tailroom = truesize - len; len -= hdr_len; offset += hdr_padded_len; p += hdr_padded_len; + shinfo_size = SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); + + if (len > GOOD_COPY_LEN && tailroom >= shinfo_size) { + skb = build_skb(p, truesize); + if (unlikely(!skb)) + return NULL; + + skb_put(skb, len); + goto ok; + } + + /* copy small packet so we can reuse these pages for small data */ + skb = napi_alloc_skb(&rq->napi, GOOD_COPY_LEN); + if (unlikely(!skb)) + return NULL; + copy = len; if (copy > skb_tailroom(skb)) copy = skb_tailroom(skb); skb_put_data(skb, p, copy); - if (metasize) { - __skb_pull(skb, metasize); - skb_metadata_set(skb, metasize); - } - len -= copy; offset += copy; @@ -427,7 +430,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, skb_add_rx_frag(skb, 0, page, offset, len, truesize); else put_page(page); - return skb; + goto ok; } /* @@ -454,6 +457,18 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, if (page) give_pages(rq, page); +ok: + /* hdr_valid means no XDP, so we can copy the vnet header */ + if (hdr_valid) { + hdr = skb_vnet_hdr(skb); + memcpy(hdr, hdr_p, hdr_len); + } + + if (metasize) { + __skb_pull(skb, metasize); + skb_metadata_set(skb, metasize); + } + return skb; }
In page_to_skb(), if we have enough tailroom to save skb_shared_info, we can use build_skb to create skb directly. No need to alloc for additional space. And it can save a 'frags slot', which is very friendly to GRO. Here, if the payload of the received package is too small (less than GOOD_COPY_LEN), we still choose to copy it directly to the space got by napi_alloc_skb. So we can reuse these pages. Testing Machine: The four queues of the network card are bound to the cpu1. Test command: for ((i=0;i<5;++i)); do sockperf tp --ip 192.168.122.64 -m 1000 -t 150& done The size of the udp package is 1000, so in the case of this patch, there will always be enough tailroom to use build_skb. The sent udp packet will be discarded because there is no port to receive it. The irqsoftd of the machine is 100%, we observe the received quantity displayed by sar -n DEV 1: no build_skb: 956864.00 rxpck/s build_skb: 1158465.00 rxpck/s Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> Suggested-by: Jason Wang <jasowang@redhat.com> --- drivers/net/virtio_net.c | 51 ++++++++++++++++++++++++++-------------- 1 file changed, 33 insertions(+), 18 deletions(-)