On Thu, Jan 28, 2016 at 01:51:02PM +0000, David Laight wrote: > From: Marcelo Ricardo Leitner > > Sent: 27 January 2016 17:07 > > This patchset is merely a RFC for the moment. There are some > > controversial points that I'd like to discuss before actually proposing > > the patches. > > You also need to look at how a 'user' can actually get SCTP to > merge data chunks in the first place. > > With Nagle disabled (and it probably has to be since the data flow > is unlikely to be 'command-response' or 'unidirectional bulk') > it is currently almost impossible to get more than one chunk > into an ethernet frame. > > Support for MSG_MORE would help. > > Given the current implementation you can get almost the required > behaviour by turning nagle off and on repeatedly.
That's pretty much expected, I think. Without Nagle, if bandwidth and cwnd allow, segment will be sent. GSO by itself shouldn't cause a buffering to protect from that. If something causes a bottleneck, tx may get queue up. Like if I do a stress test in my system, generally receiver side is slower than sender, so I end up having tx buffers pretty easily. It mimics bandwidth restrictions. There is also the case of sending large data chunks, where sctp_sendmsg() will segment it into smaller chunks already. But yes, agreed, MSG_MORE is at least a welcomed compliment here, specially for applications generating a train of chunks. Will put that in my ToDo here, thanks. > I did wonder whether the queued data could actually be picked up > be a Heartbeat chunk that is probing a different remote address > (which would be bad news). I don't follow. You mean if a heartbeat may get stuck in queue or if sending of a heartbeat can end up carrying additional data by accident? Marcelo
