[tor-relays] big spike in cpu usage

[N Owen Gunden]

On Sat, Apr 06, 2013 at 09:33:11PM +0600, Roman Mamedov wrote:
> You can check if your host has throttled/limited your total CPU usage.
> 
> I like this completely unscientific quick test that doesn't require
> installing any extra software:
> 
>   dd if=/dev/zero bs=1M count=1024 | md5sum
> 
> Should return 250-400 MB/sec on a modern CPU.
> 
> Check if you get significantly less. E.g. on one host I had about 80-100 MB
> only, despite /proc/cpuinfo and the like all showing normal CPU frequencies,
> so couldn't tell there was any throttling other than from testing.

40 MB/sec :(.

Granted, the VPS was marketed as a storage server. I simply thought to run
tor on there because it mostly sits idle. I believe it is a xen-based VM.

Some more specs: 1G of RAM, cpu is described as 6/6
(SPECint_rate2006/SPECfp_rate2006).

# cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family  : 6
model   : 44
model name  : Intel(R) Xeon(R) CPU           E5606  @ 2.13GHz
stepping  : 2
cpu MHz   : 2133.476
cache size  : 8192 KB
fpu   : yes
fpu_exception : yes
cpuid level : 11
wp    : yes
flags   : fpu de tsc msr pae cx8 sep cmov pat clflush mmx fxsr sse sse2 ss ht syscall nx lm constant_tsc up rep_good aperfmperf pni pclmulqdq ssse3 cx16 sse4_1 sse4_2 popcnt aes hypervisor lahf_lm arat
bogomips  : 4266.95
clflush size  : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:


My issue seems to come and go. For example, right now I'm running with:

  RelayBandwidthRate 120 KB
  RelayBandwidthBurst 240 KB

and using all of 1% CPU.

(as a reminder, the other day I was running at 40KB/80KB and pegging the cpu.)

Does tor traffic generally fluctuate a lot with time of day?