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Date: Mon, 12 Aug 2013 02:06:31 +0100
From: Rafael Waldo Delgado Doblas <lord.rafa@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: Parallella: Litecoin mining
Hello,
2013/8/10 Solar Designer <solar@...nwall.com>
> This is good news, although the target performance is much higher - I'd
> guesstimate 3 kh/s with pure C and 4-5 kh/s with asm code. (We had a
> smaller difference between pure C and asm for Katja's bcrypt code - with
> best asm speed being about 20% higher than best C speed - but for scrypt
> I'd expect a bigger difference due to potential use of IMADD for bit
> rotates, and due to Salsa20 containing relatively more ADDs than XORs,
> as compared to Blowfish.)
>
> OK. At a later time, you could even try 4.5, if you make your code
> really compact. (Of course, supporting a TMTO factor that is not a
> whole number requires slightly different code.)
>
> I think at this time your priority should be to find out why you're not
> getting more than 1.15 kh/s at TMTO factor 6. You could get something
> like 2+ kh/s with pure C code with it, with more optimal code (this is
> just my gut feeling, though).
>
> Is the code based off scrypt's -ref or -nosse? Anyhow, even -nosse
> performed a lot of unnecessary data copying. This is something I
> optimized in escrypt, but only in -sse code. If the problem is indeed
> still present in the code you're using, you could compare escrypt's
> crypto_scrypt-sse.c against the original in scrypt-1.1.6.tgz and
> implement similar optimizations (I mean removing blkxor and blkcpy) for
> whatever code revision you have.
>
>
Ok I working on it right now.
It looks reasonable to me, except that I did not expect you'd have this
> much pre-initialized data (2.5 KB). What is it?
>
Mmm almost 1.4K is "volatile shared_buf_t M[16] SECTION("shared_dram");"
Actually I don’t know why because is not pre-initialized.
The rest is weird because even if only have the main function without
anything more, I got 1128B of pre-initialized data.
> > Why the only information is about text, data and bss sections?.
>
> What else did you expect to see there? Your scratch space that you use
> for scrypt's V? How do you allocate it?
>
There other sections defined in the linker scrypt:
.shared_dram for example.
The scratch space is defined as static memory "char
scratchpad[SCRATCHBUF_SIZE];"
Regards,
Rafael.
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