From: Linus Torvalds <torvalds@linux-foundation.org>
To: Steven Noonan <steven@uplinklabs.net>
Cc: "Giuseppe Scrivano" <gscrivano@gnu.org>,
"Pádraig Brady" <P@draigbrady.com>,
Bug-coreutils@gnu.org, "Git Mailing List" <git@vger.kernel.org>
Subject: Re: Linus' sha1 is much faster!
Date: Mon, 17 Aug 2009 09:22:56 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.2.01.0908170852320.3162@localhost.localdomain> (raw)
In-Reply-To: <f488382f0908170844h649126efxb27f87d7b319961b@mail.gmail.com>
On Mon, 17 Aug 2009, Steven Noonan wrote:
>
> Interesting. I compared Linus' implementation to the public domain one
> by Steve Reid[1]
You _really_ need to talk about what kind of environment you have.
There are three major issues:
- Netburst vs non-netburst
- 32-bit vs 64-bit
- compiler version
Steve Reid's code looks great, but the way it is coded, gcc makes a mess
of it, which is exactly what my SHA1 tries to avoid.
[ In contrast, gcc does very well on just about _any_ straightforward
unrolled SHA1 C code if the target architecture is something like PPC or
ia64 that has enough registers to keep it all in registers.
I haven't really tested other compilers - a less aggressive compiler
would actually do _better_ on SHA1, because the problem with gcc is that
it turns the whole temporary 16-entry word array into register accesses,
and tries to do register allocation on that _array_.
That is wonderful for the above-mentioned PPC and IA64, but it makes gcc
create totally crazy code when there aren't enough registers, and then
gcc starts spilling randomly (ie it starts spilling a-e etc). This is
why the compiler and version matters so much. ]
> (average of 5 runs)
> Linus' sha1: 283MB/s
> Steve Reid's sha1: 305MB/s
So I get very different results:
# TIME[s] SPEED[MB/s]
Reid 2.742 222.6
linus 1.464 417
this is Intel Nehalem, but compiled for 32-bit mode (which is the more
challenging one because x86-32 only has 7 general-purpose registers), and
with gcc-4.4.0.
Linus
next prev parent reply other threads:[~2009-08-17 16:23 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-14 23:25 Linus' sha1 is much faster! Pádraig Brady
2009-08-15 20:02 ` Bryan Donlan
2009-08-15 20:12 ` John Tapsell
2009-08-15 20:23 ` Linus Torvalds
2009-08-15 20:54 ` Linus Torvalds
2009-08-17 1:55 ` Nicolas Pitre
2009-08-26 11:39 ` Pádraig Brady
2017-04-20 21:35 ` galt
2017-04-20 21:38 ` galt
2009-08-17 8:22 ` Andreas Ericsson
2009-08-16 0:06 ` Theodore Tso
2009-08-16 19:25 ` Giuseppe Scrivano
2009-08-16 20:10 ` Linus Torvalds
2009-08-16 22:15 ` Giuseppe Scrivano
2009-08-16 22:47 ` Linus Torvalds
2009-08-17 1:53 ` Pádraig Brady
2009-08-17 10:51 ` Giuseppe Scrivano
2009-08-17 15:44 ` Steven Noonan
2009-08-17 16:22 ` Linus Torvalds [this message]
2009-08-17 21:43 ` Steven Noonan
2009-08-17 17:32 ` Giuseppe Scrivano
-- strict thread matches above, loose matches on Subject: below --
2009-08-17 7:23 George Spelvin
2009-08-17 14:20 ` Nicolas Pitre
2009-08-17 17:06 ` Nicolas Pitre
2009-08-17 17:20 ` Paolo Bonzini
2009-08-17 18:54 ` George Spelvin
2009-08-17 19:34 ` Nicolas Pitre
2009-08-17 23:12 ` George Spelvin
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