Yeah, the real nice thing is TCP_NOTSENT_LOWAT added in linux-3.12
On Wed, 2015-04-22 at 12:28 -0700, Dave Taht wrote: > SO_SNDLOWAT or something similar to it with a name I cannot recall, > can be useful. > > On Wed, Apr 22, 2015 at 12:10 PM, Hal Murray <[email protected]> wrote: > > > >> As I understand it (I thought) SO_SNDBUF and SO_RCVBUF are socket buffers > >> for the application layer, they do not change the TCP window size either > >> send or receive. Which is perhaps why they aren't used much. They don't do > >> much good in iperf that's for sure! Might be wrong, but I agree with the > >> premise - auto-tuning should work. > > > > I sure expect them to do the obvious thing. > > > > man 7 socket says: > > > > SO_SNDBUF > > Sets or gets the maximum socket send buffer in bytes. > > > > It doesn't actually say that turns into the TCP window size. > > > > On Linux, there is a factor of 2 for overhead and whatever. > > > > man tcp says: > > TCP uses the extra space for administrative purposes and inter- > > nal kernel structures, and the /proc file values reflect the > > larger > > sizes compared to the actual TCP windows. > > > > So it looks like the number you feed it turns into the window size. > > > > A few quick tests with netperf confirm that it is doing something close to > > what I expect but I haven't fired up tcpdump to verify that the window size > > is what I asked for. netperf does print out values that are 2x what I asked > > for. > > > > Yuck. (That's Yuck at Linux, not netperf.) > > > > > > -- > > These are my opinions. I hate spam. > > > > > > > > _______________________________________________ > > Bloat mailing list > > [email protected] > > https://lists.bufferbloat.net/listinfo/bloat > > > _______________________________________________ Bloat mailing list [email protected] https://lists.bufferbloat.net/listinfo/bloat
