On 2019/4/8 下午5:44, Stefan Hajnoczi wrote:
On Mon, Apr 08, 2019 at 02:43:28PM +0800, Jason Wang wrote:
Another thing that may help is to implement sendpage(), which will greatly
improve the performance.
I can't find documentation for ->sendpage(). Is the idea that you get a
struct page for the payload and can do zero-copy tx?
Yes.
(And can userspace
still write to the page, invalidating checksums in the header?)
Stefan
Userspace can still write to the page, but for correctness (e.g in the
case of SPLICE_F_GIFT describe by vmsplice(2)), it should not do this.
For vmsplice, it may hard to detect the time to reuse the page. Maybe we
MSG_ZEROCOPY[1] is better.
Anyway, sendpage() could be still useful for sendfile() or splice().
Thanks
[1] https://netdevconf.org/2.1/papers/netdev.pdf
