Torrent with no peers eats up resources?

[Haravikk]

I posted in a thread a little while ago regarding problems with Transmission slowing down, originally thinking it to be the number of peers. However, no combination of peer values made any difference, I have also since upgraded my router to a much better one (because the previous one was dying), so it's definitely not the number of peers that is the issue, as it can handle hundreds of connections without any noticeable degradation.

However, I've still been having the same problem(s); eventually Transmission will slow down and take my internet connection with it, apparently consuming all of my available bandwidth and/or swamping my router with connections (far more than the number of peers I've set), unfortunately I've no way to diagnose this to be certain. Other symptoms include that it can take several minutes for Transmission to quit on my 8-core Mac Pro, when normally it quits almost instantly.

So I started wracking my brain, when I remembered that I have a few torrents in my list that aren't doing anything. That is; the torrents are still valid, but there are rarely any peers available, so what I was doing was keeping them in my list as they're almost finished, holding on the hope that someone with 100% of the file(s) will come online so I can finish it. It's now long-past the point where it's worth waiting any more.

Today, I had the same slow-down occur, much faster than usual (it normally happens after quite a while, later in the day), and decided to try removing these idle torrents, and my download rate immediately jumped back up, and Safari etc. became more responsive again.

So I'm thinking the culprit in this case may be such torrents, where the tracker is valid but there are no peers, it's as if Transmission is getting itself into some kind of loop that is crushing performance not just for it, but every other application on my computer. It's the Mac OS X version I'm using, though I'm not sure it's an OS X specific bug. I also have encrypted clients required, as otherwise my bittorrent performance is throttled very quickly.

[Waldorf]

The only time T really affects the overall performance is when it needs to verify a file/torrent. Also, If you're writing to an USB or shared disk, and a file is being allocated (because T received a piece) that may also take some cpu. As for the Quit times, that is *normal* since T has to report stats to the tracker, but when a tracker is being slow to respond, this may take up to a min. (same as when T was was first announcing to a tracker when you quit, I guess)

[Haravikk]

Those clearly aren't the only cases though, perhaps they should be, but as I said; the torrents I had with no peers were apparently hogging resources, they shouldn't have been causing any hard-drive activity as nothing was being received, and no verification was being performed. The torrents were just sitting there with no upload-speed, and no download-speed, and no-peers, in the hopes that eventually someone who did have that last 1% would come online.

And yet, after some period of them sitting like this, my network ground to a halt. After having this happen several times, and me identifying Transmission as the culprit (quitting fixed it immediately), then I started wondering why Transmission would do that. So I adjustment peer numbers etc., which not improvement. Then when it happened again I decided to try removing the "idle" torrents and the improvement was instantaneous.

[Haravikk]

I'm still having this problem, forcing me to close Transmission whenever it gets into this resource-hogging state. Pausing torrents which are causing this issue doesn't seem to do anything to help, only removing the torrents completely resolves this.
Transmission is doing /something/ with these torrents but I can't find any way of discovering what, but whatever it is it is creating enough network traffic to saturate my internet connection, forcing me to either start removing torrents so I can continue with the ones I want most, or close Transmission and try again later (usually next-day).

Can a Transmission developer please comment? I'd really like a custom Transmission build with some debug-tools; since this happening to me fairly consistently it would help a lot in tracking down what exactly the problem is. I really don't want to have to switch a different torrent client, as the others for OS X are pretty poor.

[volenin]

I do confirm the same issue - transmission does have adverse effect on the network in the described manner. Using SVN build 7931.

Vlad