Date: Sat, 29 Feb 2020 16:39:48 +0100 From: Solar Designer <solar@...nwall.com> To: john-users@...ts.openwall.com Subject: Re: PCI express On Sat, Feb 29, 2020 at 10:16:44AM -0500, Powen Cheng wrote: > Do you know or anyone know if tezos2john.py > <https://github.com/magnumripper/JohnTheRipper/blob/bleeding-jumbo/run/tezos2john.py> > this type of cracking, Will the speed of the pci express matter much? This is a slow (non-)hash, and won't be impacted by PCIe bandwidth much. However, our implementation of the tezos-opencl format also makes significant use of CPU, so if you're looking into connecting lots of GPUs e.g. via flexible PCIe extenders to a cheap motherboard/CPU then the CPU will become the bottleneck. IIRC, we already saw this with cloud instances with 8x Tesla V100, where the corresponding fast dual CPUs (IIRC, with a total of 96 logical CPUs) were not quite fast enough to fully use these very fast GPUs. Regardless, one trick to hide the latency (only latency, not low performance) of both CPU computation and PCIe transfer is to run two processes per GPU - that is, use "--fork=N" with N being twice the number of GPUs. This will only work well if the number of logical CPUs much greater than the number of GPUs. Realistically, you won't reasonably use more than a few GPUs per machine with our current tezos-opencl format. As I mention, 8 very fast GPUs is already too many even for the fastest CPUs. Alexander
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.