Re:Boosting upload speed and improving Windows' TCP stack
by toast0 on Wednesday May 19, 2021 @01:13PM
(#27211513)
On further reflection, I just want to emphasize how much of an improvement RSS/PCBGROUP and the couple of minor tweaks made for this use case; with unmodified FreeBSD 12 and HAProxy and the load we had, there was basically zero conncurrency available, you could run as many processes (or threads) as you wanted, and the capacity would be the same, and it was sad, I think we could only get about 100k clients on a box before it would run out of steam.
With everything tweaked, we got to 2M clients per server, and actually it was hard to find the limit, because I wasn't able to direct enough traffic to the machines under test.
The software and configuration changes weren't big, but it was a huge impact. On the other hand, if RSS and PCBGROUP weren't in the kernel, I don't think I would have been able to add something similar, and we would have had to something wild and crazy (or try Linux and see if it would do the job). Now, I really did want to write a raw packet tcp proxy in userspace, but I knew it would be a lot easier to manage and quicker to get working with something off the shelf.
Of course, maybe there's a better solution to the root bottleneck, which was always opening a new outgoing tcp connection; even with all the tweaks, that was still the bottleneck, but fixing that needs someone more skilled than me, and I guess it's a pretty niche use case to be opening so many outgoing sockets. Accepting tons of sockets is way more common and way more optimized.
With everything tweaked, we got to 2M clients per server, and actually it was hard to find the limit, because I wasn't able to direct enough traffic to the machines under test.
The software and configuration changes weren't big, but it was a huge impact. On the other hand, if RSS and PCBGROUP weren't in the kernel, I don't think I would have been able to add something similar, and we would have had to something wild and crazy (or try Linux and see if it would do the job). Now, I really did want to write a raw packet tcp proxy in userspace, but I knew it would be a lot easier to manage and quicker to get working with something off the shelf.
Of course, maybe there's a better solution to the root bottleneck, which was always opening a new outgoing tcp connection; even with all the tweaks, that was still the bottleneck, but fixing that needs someone more skilled than me, and I guess it's a pretty niche use case to be opening so many outgoing sockets. Accepting tons of sockets is way more common and way more optimized.