Date: Thu, 5 Jul 2012 09:17:52 +0400 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: About very high memory usage On Thu, Jul 05, 2012 at 11:24:59AM +0800, myrice wrote: > In my xsha512-cuda, I set MIN_KEYS_PER_CRYPT=MAX_KEYS_PER_CRYPT = > 128*1024. So it allocates 128*1024 keys and hashes. [...] > However, when I do ./john -te=xsha512-cuda > ../jtrTestSuite/XSHA512_tst.in . The john uses up to 4.4GB memory on > bull. [...] > Besides, in self test or if I gave a wordlist to john, mean I do > ./john -te=xsha512-cuda ../jtrTestSuite/XSHA512_tst.in > -wo=../jtrTestSuite/pw.dic, it will not take so much memory. > > I just curious about it. Does single or incremental mode uses so much memory? Single crack mode does when you set min_keys_per_crypt this high, which was not expected when I designed this mode in almost its current form in 1998. We have two settings - min_keys_per_crypt and max_keys_per_crypt - precisely to make single crack mode behave better. The "min" should in fact be as low as possible while achieving reasonable performance. It is OK if the performance achieved at that setting is, say, twice worse than at "max". What would your "min" need to be for that? And if we allow for 10x worse c/s rate? BTW, if you load more hashes (or rather, more different salts), memory usage will grow even further, because single crack mode allocates full candidate password buffers (for min_keys_per_crypt passwords) per salt. Alexander
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