Date: Wed, 16 Sep 2015 05:57:21 +0300 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: larger bitmaps and hash tables On Wed, Sep 16, 2015 at 05:28:17AM +0300, Solar Designer wrote: > With SHR=1: > > real 0m52.976s > user 3m39.218s > sys 0m16.227s Another doubling of bitmap size while keeping the hash table size same: #define PASSWORD_HASH_SIZE_6 0x20000000 #define PASSWORD_HASH_SHR 2 real 0m50.480s user 3m19.678s sys 0m17.056s And one more: #define PASSWORD_HASH_SIZE_6 0x40000000 #define PASSWORD_HASH_SHR 3 real 0m50.080s user 3m9.933s sys 0m18.377s And one more: #define PASSWORD_HASH_SIZE_6 0x80000000 #define PASSWORD_HASH_SHR 4 real 0m50.453s user 3m7.901s sys 0m20.535s Somehow a regression, and system time increase. Maybe the page table entries became too large to fit in a cache. (And we were having mostly TLB misses anyway.) Maybe use of "huge pages" for the bitmap and the hash table would help. BTW, the actual cracking takes just 21 to 23 seconds (varies across the 8 processes), meaning that the loading is 27 seconds. We should be able to optimize the loading somewhat. To make these experiments easier, I adjusted the *_6() hash functions to use (PASSWORD_HASH_SIZE_6 - 1) for the mask. Perhaps we should make this standard practice. Alexander
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