On 03/05/2018 09:42 PM, David Miller wrote: > From: John Fastabend <john.fastab...@gmail.com> > Date: Mon, 5 Mar 2018 14:53:08 -0800 > >> I decided to make the default no-copy to mirror the existing >> sendpage() semantics and then to add the flag later. The flag >> support is not in this series simply because I wanted to get the >> base support in first. > > What existing sendpage semantics are you referring to? >
All I meant by this is if an application uses sendfile() call there is no good way to know when/if the kernel side will copy or xmit the data. So a reliable user space application will need to only modify the data if it "knows" there are no outstanding sends in-flight. So if we assume applications follow this then it is OK to avoid the copy. Of course this is not good enough for security, but for monitoring/statistics (my use case 1 it works). By keep existing sendpage semantics I just meant applications should already follow the above.
