From: David Miller <davem@davemloft.net>
To: bharrosh@panasas.com
Cc: npiggin@gmail.com, hooanon05@yahoo.co.jp, npiggin@kernel.dk,
torvalds@linux-foundation.org, linux-arch@vger.kernel.org,
x86@kernel.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: Big git diff speedup by avoiding x86 "fast string" memcmp
Date: Wed, 15 Dec 2010 10:00:55 -0800 (PST) [thread overview]
Message-ID: <20101215.100055.226772943.davem@davemloft.net> (raw)
In-Reply-To: <4D08BF5D.1060509@panasas.com>
From: Boaz Harrosh <bharrosh@panasas.com>
Date: Wed, 15 Dec 2010 15:15:09 +0200
> I agree that the byte-compare or long-compare should give you very close
> results in modern pipeline CPUs. But surly 12 increments-and-test should
> show up against 3 (or even 2). I would say it must be a better plan.
For strings of these lengths the setup code necessary to initialize
the inner loop and the tail code to handle the sub-word ending cases
eliminate whatever gains there are.
I know this as I've been hacking on assembler optimized strcmp() and
memcmp() in my spare time over the past year or so.
next prev parent reply other threads:[~2010-12-15 18:00 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-09 7:09 Big git diff speedup by avoiding x86 "fast string" memcmp Nick Piggin
2010-12-09 13:37 ` Borislav Petkov
2010-12-10 2:38 ` Nick Piggin
2010-12-10 4:27 ` Nick Piggin
2010-12-10 14:23 ` J. R. Okajima
2010-12-13 1:45 ` Nick Piggin
2010-12-13 7:29 ` J. R. Okajima
2010-12-13 8:25 ` Nick Piggin
2010-12-14 19:01 ` J. R. Okajima
2010-12-15 4:06 ` Nick Piggin
2010-12-15 5:57 ` J. R. Okajima
2010-12-15 13:15 ` Boaz Harrosh
2010-12-15 18:00 ` David Miller [this message]
2010-12-16 9:53 ` Boaz Harrosh
2010-12-16 13:13 ` Nick Piggin
2010-12-16 14:03 ` Boaz Harrosh
2010-12-16 14:15 ` Nick Piggin
2010-12-16 16:51 ` Linus Torvalds
2010-12-16 17:57 ` David Miller
2010-12-15 4:38 ` Américo Wang
2010-12-15 5:54 ` Nick Piggin
2010-12-15 7:12 ` Linus Torvalds
2010-12-15 23:09 ` Tony Luck
2010-12-16 2:34 ` Nick Piggin
-- strict thread matches above, loose matches on Subject: below --
2010-12-18 22:54 George Spelvin
2010-12-19 14:28 ` Boaz Harrosh
2010-12-19 15:46 ` Nick Piggin
2010-12-19 17:06 ` George Spelvin
2010-12-21 9:26 ` Nick Piggin
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