[Tor-BSD] Recognizing Randomness Exhaustion

[Pete Wright]

On 1/1/15 9:23 PM, Libertas wrote:
> However, we're now finding that a profusion of gettimeofday() syscalls
> may be the issue. It was independently discovered by the operator of
> IPredator, the highest-bandwidth Tor relay:
>
> 	https://ipredator.se/guide/torserver#performance
>
> My 800 KB/s exit node had up to 7,000 gettimeofday() calls a second,
> along with hundreds of clock_gettime() calls.

i am seeing quite a few clock_gettime requests on a freebsd-10.1 system:

pete at tor-tracks:~ % sudo dtrace -n 'syscall::clock_gettime:entry { 
@[execname] = count(); }'
dtrace: description 'syscall::clock_gettime:entry ' matched 1 probe
^C
   syslogd                                                           1
   sendmail                                                          3
   ntpd                                                              7
   sshd                                                              8
   dtrace                                                           26
   tor                                                           25274

dtruss shows similar numbers:
pete at tor-tracks:~ % sudo dtruss -n tor -c -t clock_gettime
<snip>
CALL                                        COUNT
close                                           1
sendto                                          2
recvfrom                                        4
getpid                                         18
kevent                                        135
write                                         154
read                                          412
gettimeofday                                  447
clock_gettime                                2837



>
> Because IPredator runs Linux, he used vsyscalls to speed things up.
> We'll probably need to find something more creative, like using our time
> caching more.
>
> We're working on it with this ticket:
>
> 	https://trac.torproject.org/projects/tor/ticket/14056
>

thanks for the link i'll keep an eye on that ticket.

cheers,
-pete


-- 
Pete Wright
pete at nomadlogic.org
twitter => @nomadlogicLA