GPU utilization oscillates when cracking a rar3-p hash

[brtlmj]

I am trying to crack a rar3-p (-m 23800) hash using a dictionary:

hashcat.exe -a 0 -O -w 3 -m 23800 hashfile.txt dictionary_file.txt -o results.txt

My GPU is a RX 6600, installed in a x16 slot.

The GPU utilization (as reported by both hashcat itself and AMD tools) jumps between 0% and 99% with a period of 4-ish seconds. Average utilization seems to be close to 60%. Every once in a while I see several seconds with full utilization.

What might be going on here? I understand that rar3-p is considered to be a "slow" hash and a dictionary attack with no amplification is appropriate. Or am I wrong?

Thanks!

[Chick3nman]

Sounds like your dictionary is relatively small and/or your host is having trouble streaming it to the GPU sufficiently. The speed bump is likely because there's a period where the GPU is left without work while it waits for the host to send it the next batch of candidates.

https://hashcat.net/wiki/doku.php?id=fre...full_speed

[brtlmj]

Looks like you are right - I am running out of CPU time. When I killed all other CPU hogs, GPU utilization improved markedly.

Thanks!