On Sat, Nov 06, 2010 at 03:47:54PM +0100, Claudio Jeker wrote: > On Sat, Nov 06, 2010 at 02:13:46PM +0100, Jan Stary wrote: > > For some time now, I have been using the following sysctl's > > mentioned in FAQ 6.6.4, which sped up my network traffic > > considerably: > > > > net.inet.tcp.recvspace > > net.inet.tcp.sendspace > > net.inet.udp.recvspace > > net.inet.udp.sendspace > > > > Now that I have reinstalled with current/amd64, the tcp ones > > seem to have disappeared (while the udp ones are still there). > > > > Am I missing something? > > > > No. The TCP ones are gone, enjoy fast downloads without pushing buttons. > The automatic TCP windowscaling in -current makes the global tcp.recvspace > and tcp.sendspace superfluous.
I've found that receiving traffic from Linux hosts with timestamps turned off has decreased in performance with the new window scaling. Is this because the RTT cannot be determined. Or an oversight? The thing is in general timestamps don't seem to improve things a lot, and take up an extra 12 bytes if you're otherwise not using TCP options. I was doing tcpdumps etc, and found that basically the window size doesn't raise above 16k like the old default. But in general I've been setting TCP window size manually for a long time. I also noticed that now OpenBSD seems to be faster at sending data than Linux to my home ADSL link from a closeish connection. :) Also I was wondering if making the initial cwnd window size be tunable as been taken into consideration. As well as being able to run-time tune the maximum window size above 256k. (or below) I poked around in the source a little. And I noticed that I could tune maximum window size up to 1024k and could change the minimum window size up. But I am at a loss to understand if it's possible to use > 64k window size on hosts without timestamps (because I saw the window size set being advertised directly before it is known whether there was window scaling or not) and whether memory pressure could lead to issues from bigger buffers. ie does something else have to be raised assuming one has sufficient memory and bandwidth/latency. In my own testing I noticed a speed jump from 14 to 31 megabit going from a 256k to 1024k maximum window size. Which to me seems significant. Ben.
