Date: Mon, 14 Nov 2016 22:31:12 +0100 From: magnum <john.magnum@...hmail.com> To: john-users@...ts.openwall.com Subject: Re: Loading high number of hashes on GPU On 2016-11-14 21:48, Solar Designer wrote: > On Mon, Nov 14, 2016 at 06:18:25PM +0100, Patrick Proniewski wrote: >> Speaking about memory limit on GPU, is there any ? > > It varies by format, specific GPU, etc. > >> I've seen benches of hashcat on badass GPU using only 2GB of the 8GB VRAM available. I have not yet had the opportunity to use JtR on GPU and I wonder if the limit is the same. > > Not necessarily the same. A potentially relevant limit is what clinfo > lists as "Max memory allocation", but it varies across GPUs (can be a > different fraction of total GPU memory) and might not apply to a given > JtR format. (And we could work on making it not apply where it > currently does.) Perhaps stating the obvious but please note the difference: the "Max memory allocation" is a limit for any *single* allocation out of possibly many. It seems it's a de-facto standard to set it to a quarter of total memory (I haven't seen any GPU deviating from that). But you can do several allocs (eg. a hash buffer, a key buffer and a result buffer) for a total of up to 8 GB in Patrick's case and all of our formats will/may do so. I would think that goes for Hashcat too. However, if a *single buffer* (eg. our key buffer) would need more than the max. alloc figure, we'd need some potentially complex workaround and we don't do any such thing in current code. > magnum - I also just noticed it does try to remove duplicates. Hmm. > Anyway, that's not john-users material anymore (but is john-dev or > GitHub issue material). It? Do you mean Sayantan's bt code or what? magnum
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