#33211: proxy-go sometimes gets into a 100+% CPU state
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Reporter: dcf | Owner: (none)
Type: defect | Status: new
Priority: Medium | Milestone:
Component: Circumvention/Snowflake | Version:
Severity: Normal | Keywords:
Actual Points: | Parent ID:
Points: | Reviewer:
Sponsor: |
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proxy-go sometimes works itself into a state where it is still running and
working, but using more than 100% CPU. I have had it happen locally a
couple of times while testing turbotunnel stuff, and it's currently
happening with proxy-go-restartless:
{{{
$ top
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+
COMMAND
13844 snowfla+ 20 0 551292 320692 8844 R 161.1 15.6 129356:18 proxy-
go
}}}
Or looking at single threads:
{{{
$ top -H
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
24628 snowfla+ 20 0 551292 320692 8844 R 39.7 15.6 15219:01 proxy-
go
13844 snowfla+ 20 0 551292 320692 8844 R 35.4 15.6 15431:52 proxy-
go
1637 snowfla+ 20 0 551292 320692 8844 R 34.8 15.6 16057:40 proxy-
go
13848 snowfla+ 20 0 551292 320692 8844 S 27.5 15.6 13669:02 proxy-
go
13846 snowfla+ 20 0 551292 320692 8844 S 22.5 15.6 17021:57 proxy-
go
}}}
I caught it once and attached to the process with GDB, but didn't know
what to make of it. `thread apply all bt` seemed to show all the threads
being somewhere in the Go runtime; the thread that wasn't was not one of
the threads using a lot of CPU. (Matching up the `PID` field from `top -H`
with the `LWP` identifiers in gdb.)
I had the idea to make proxy-go emit profiling output, and then exmine the
call chain that was resulting the in the most CPU using
[https://blog.golang.org/profiling-go-programs profiling tools]. A patch
to do that is attachment:proxy-go-profile.patch. But I haven't been able
to reproduce the high CPU usage yet.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/33211>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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