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Date: Thu, 1 Aug 2013 00:33:18 +0200
From: Katja Malvoni <kmalvoni@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: Parallella: bcrypt
On Thu, Aug 1, 2013 at 12:22 AM, Solar Designer <solar@...nwall.com> wrote:
> > I'm using two
> > structs but both are still in the same struct called shared_buffer. And I
> > have an interesting situation - I have a code which isn't reliable
> > (sometimes fails self test), but when it works I get very weird speed:
> > 497619 c/s (it's not constant but it's 49xxxx, both real and virtual). I
> am
> > testing bcrypt-parallella format, I only changed how data is transferred
> > and how result is read (separated structs for input and output, I still
> > haven't implemented savings when salt or keys aren't changed). I don't
> > understand this speed. If I measure time with transfers it's around 0.05
> > ms. But with unoptimized bcrypt, speed of computing the hash without
> > transfers was around 16.5 ms. If I read whole outputs struct and than use
> > memcpy to have result in parallella_BF_out speed is 1204 c/s. Code which
> > gives this very high speed is committed.
>
> I guess this line:
>
> buff.out.core_done[corenum] = 0;
>
> is not executing or does not take effect (as far as the host is aware)
> soon enough. You appear to have a race condition here, and it appears
> to be triggered 100% of the time now. I guess you need to be resetting
> core_done[corenum] to 0 from the host, not from Epiphany.
>
Actually, that line works, that's why if I do second read after while loop
code works. But I made a stupid mistake - when changing how data is
transferred I changed variable used as condition in polling while loop and
I wasn't resetting it to zero. And it was passing self test because old
data remained in shared dram.
Speed is 1204 c/s.
Katja
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