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Date: Sat, 9 May 2015 22:39:34 +0800
From: Lei Zhang <zhanglei.april@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: Adding OpenMP support to SunMD5
> On May 9, 2015, at 7:31 PM, Solar Designer <solar@...nwall.com> wrote:
>>
>> [lei@...er src]$ ../run/john --test --format=sunmd5
>> Will run 32 OpenMP threads
>> Benchmarking: SunMD5 [MD5 128/128 AVX 4x3]... (32xOMP) DONE
>> Speed for cost 1 (iteration count) of 5000
>> Raw: 4954 c/s real, 162 c/s virtual
>>
>> Hints?
>
> Please try the hints from super's /etc/motd, in particular "export
> GOMP_CPU_AFFINITY=0-31" Does it help?
Yes, it helps!
[lei@...er src]$ GOMP_CPU_AFFINITY=0-31 ../run/john --test --format=sunmd5
Will run 32 OpenMP threads
Benchmarking: SunMD5 [MD5 128/128 AVX 4x3]... (32xOMP) DONE
Speed for cost 1 (iteration count) of 5000
Raw: 7372 c/s real, 231 c/s virtual
I also tested it with my previous version, where threadprivate is used.
[lei@...er src]$ GOMP_CPU_AFFINITY=0-31 ../run/john --test --format=sunmd5
Will run 32 OpenMP threads
Benchmarking: SunMD5 [MD5 128/128 AVX 4x3]... (32xOMP) DONE
Speed for cost 1 (iteration count) of 5000
Raw: 8302 c/s real, 259 c/s virtual
The newer version is still slower.
> Other than that, it is possible that you ran into false sharing. Having
> a gap between the different threads' data structures can be beneficial.
I'm not sure about that. I just multiply the size of the original arrays by the number of threads. There should be no cross-referencing among threads.
Dynamic arrays have slower accessing than static arrays. Could that be the reason of performance degeneration?
Lei
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