Transmission causes leopard slow death

[funkahdafi]

will anyone of the developers ever have a word about this here?

[funkahdafi]

I noticed something else. As soon as I download more than one torrent with a lot (a lot) of seeds and download bandwidth, transmission becomes almost unusable. The interface freezes completely and only comes back once in a while for about 1 second, just to freeze again. In these same situations I had previously experienced the beginning of "slow death". Now that I turned off speed limits, I don't see slow death anymore, but the interface problem remains.

I think we have some major issue here.

[NexX]

I've found a solution in two steps (in my case, at least)...

1. Set speed limit to 1MB/S

2. Set Maximum Torrent Download at 1 (1 at a time in a queue)

Hope this helps

[kidmidnight]

The ticket for this is hilarious. the developers have closed it like 5 times now. lol, but nothing has been fixed.

[funkahdafi]

well fortunately utorrent is out there too.

[NexX]

well fortunately utorrent is out there too.

uTorrent doesn't even download anything in my case. It can connect to the tracker, but won't download

[parodyr]

As said in my previous posts, I believe this is a networking stack issue in Leopard, which is only triggered by Transmission's behavior.

If anyone can reproduce this with Tiger, it would destroy my theory, but since I haven't seen this with Tiger, I believe it has something to do with the Leopard's automatic TCP optimization, which in case of Transmission seems to use up huge amount of memory or something.

Looking through some reports on the internet with respect to "freezing", "tcp window size", etc., I found a small reference somewhere (sorry, lost the link) stating that "... too high a window buffer might freeze/kill the network stack, if the kernel settings (NMBCLUSTERS) is not high enough..."

The nmbclusters is set to 32768, which should be high enough for all applications.

I'm not sure, what exactly the problem is, but I "switched off" Leopard's auto-tuning and set low window-sizes as well as window-scale-factor to 1.

Code: Select all

net.inet.tcp.rfc1323=0
net.inet.tcp.recvspace=32768
net.inet.tcp.sendspace=32768
net.inet.tcp.win_scale_factor=1
net.inet.tcp.sockthreshold=0

So far, my Transmission is (finally) running fine (knock-at-wood). I'll see what happens when it hits 800KiBi/s (this was usually the download speed when it started killing Leopard).

I must say, I'm still keeping "unlimited number of downloads" (currently around 70+ downloads).

I'm pretty sure the bug is somewhere in the networking code, but was, until now, not able to fully understand Transmission's networking code, I'm stilly trying to grasp the complex code. Every time, I understand a little more, I'll do some more experiments and report back.

Best
parodyr

[kidmidnight]

awesome man. I can confirm this doesnt happen under tiger. I actually have an old mini running tiger and Transmission and it doesnt happen at all. On my imac it didnt start until i installed leopard. I think you have found the issue.

[NexX]

Thanks for your research, parodyr. Let's hope the Transmission team sees this soon so we can turn your conclusions into bugfixes.

[parodyr]

Just a quick note: So far, my Transmission is running fine with 77 downloads, at somewhere around 700-950 KB/s (Downstream 50 KB/s; sorry, but I have only 16/1 Mbps ADSL+).

No problems whatsoever. I am running Transmission 1.51+ (8164), and I have the feeling that it's really faster than before - at least, it behaves a lot more "fluid" than it ever did.

Will keep you updated.

[Yada]

This could be great news, but as far as I understand it also means the bug is on Apple's end, correct?

[parodyr]

This could be great news, but as far as I understand it also means the bug is on Apple's end, correct?

Basically, it could be a bug on Apple's side, triggered only by Transmission's heavy usage of connections, mbufs, etc - i.e. a bug, which only exists in combination between Transmission and Leopard, since uTorrent (or Vuze) seem not to trigger this behavior. On the other hand, it might also be just a red herring, what I am hunting after here... Let's see. I'll do some more experiments during the next couple of days to trigger this behavior and report back.

On the other hand, if this is really the bug, then we at least could have a workaround with the settings I'm experimenting with.

[John Clay]

For those that are having continued problems, please try the latest nightly build, available here:
http://transmission.xpjets.com/

NOTE: These require 10.5 Leopard

Let us know of any problems, improvements, or explosions.

[Gaffophone]

Well with this version everything is fine for now, thanks !

[NexX]

It didn't fix it for me However, I have noticed that I can boost my speed limit a little higher without the system freezing