Xuan Zhuo wrote:
On Wed, 17 Feb 2021 16:46:04 -0800, John Fastabend [off-list ref] wrote:
quoted
Alexander Lobakin wrote:
quoted
From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
This patch is used to construct skb based on page to save memory copy
overhead.
This function is implemented based on IFF_TX_SKB_NO_LINEAR. Only the
network card priv_flags supports IFF_TX_SKB_NO_LINEAR will use page to
directly construct skb. If this feature is not supported, it is still
necessary to copy data to construct skb.
---------------- Performance Testing ------------
The test environment is Aliyun ECS server.
Test cmd:
xdpsock -i eth0 -t -S -s <msg size>
Test result data:
size 64 512 1024 1500
copy 1916747 1775988 1600203 1440054
page 1974058 1953655 1945463 1904478
percent 3.0% 10.0% 21.58% 32.3%
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
[ alobakin:
- expand subject to make it clearer;
- improve skb->truesize calculation;
- reserve some headroom in skb for drivers;
- tailroom is not needed as skb is non-linear ]
Signed-off-by: Alexander Lobakin <redacted>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
---
[...]
quoted
+ buffer = xsk_buff_raw_get_data(pool, addr);
+ offset = offset_in_page(buffer);
+ addr = buffer - pool->addrs;
+
+ for (copied = 0, i = 0; copied < len; i++) {
+ page = pool->umem->pgs[addr >> PAGE_SHIFT];
Looks like we could walk off the end of pgs[] if len is larger than
the number of pgs? Do we need to guard against a misconfigured socket
causing a panic here? AFAIU len here is read from the user space
descriptor so is under user control. Or maybe I missed a check somewhere.
Thanks,
John
Don't worry about this, the legality of desc has been checked.
xskq_cons_peek_desc -> xskq_cons_read_desc ->
xskq_cons_is_valid_desc -> xp_validate_desc
Ah OK I didn't dig past the cons_read_desc(). In that case LGTM.
Acked-by: John Fastabend <john.fastabend@gmail.com>