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Re: tor eating CPU time
On Fri, Jan 28, 2005 at 12:56:12PM +0100, Valient Gough wrote:
> I upgraded to 0.0.9.3 last weekend, and it dropped tor's average CPU
> usage by almost half.
> However thing have been slowly getting worse. Saturday stats show about
> 30% CPU average usage, increasing slowly to a little over 40% on Wed,
> then about 50% by Thursday, and about 12 hours ago tor jumped to 100%
> cpu usage and has not taken a rest since then.
> The strange thing is that this doesn't correlate with traffic served.
> Tor traffic has been steadily averaging about 200k/sec, and started
> dropping about 12 hours ago by as much as a factor of 2 (much higher
> variation though). So, CPU time increased, but network traffic decreased...
> Looking through my server monitoring logs, I don't see any correlation
> against network usage or number of open TCP connections. I'm about to
> restart TOR, but before I get into the habbit of periodic restarts, is
> there anything I can do to get information about the problem?
As near as I can tell it, Tor spends most of its time doing SSL handshakes
with other Tors (either clients or servers).
I don't think anybody has given me profiling output lately (gprof,
oprofile, etc) on a really busy server though. If you wanted to give
that a go and let me know where it spends its time _once it gets to 100%
cpu use_, that would be really handy.
For example, I can imagine a couple situations where it would start
doing linear lookups on a list of circuits that has grown really large --
and it would do such a lookup for each cell that it handles. But until
I know what's going on, trying to optimize everything is just going to