When I start rtorrent with ~20 torrents and an effective traffic of a few 100KB/s, after a short while the machine falls off the net. When I do ping then, I see ping: sendto: No buffer space available And what you do see in dmesg? 20 torrents anad ~20 TCP connections each, all with data, uses a vast number of mbuf clusters. If in -current the limit is high enough not to deny allocating those clusters, then it seems likely you are running low on kernel memory in general and perhaps hitting some untested error case. I would enable DIAGNOSTIC if you haven't already.
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