From: Bill Gatliff <bgat@billgatliff.com>
To: Dominik Bozek <domino@mikroswiat.pl>
Cc: linuxppc-embedded@ozlabs.org
Subject: Re: performance: memcpy vs. __copy_tofrom_user
Date: Wed, 08 Oct 2008 10:39:31 -0500 [thread overview]
Message-ID: <48ECD433.2080706@billgatliff.com> (raw)
In-Reply-To: <48ECC611.3030309@mikroswiat.pl>
Dominik Bozek wrote:
> Hi all,
>
> I have done a test of memcpy() and __copy_tofrom_user() on the mpc8313.
> And the major conclusion is that __copy_tofrom_user is more efficient
> than memcpy. Sometimes about 40%.
Have you looked at the two implementations? I'm not as well-versed on PPC as
ARM, but I know the latter's __copy_* functions are optimized to be almost
unintelligible. If your benchmark memcpy() implementation isn't, then you
aren't comparing apples-to-apples.
40% improvement is within what I could imagine getting from a hand-crafted,
no-holds-barred memcpy() implementation. I'd look more carefully at that code.
b.g.
--
Bill Gatliff
bgat@billgatliff.com
next prev parent reply other threads:[~2008-10-08 16:10 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-10-08 14:39 performance: memcpy vs. __copy_tofrom_user Dominik Bozek
2008-10-08 15:31 ` Minh Tuan Duong
2008-10-08 15:39 ` Bill Gatliff [this message]
2008-10-08 15:42 ` Grant Likely
2008-10-09 2:34 ` Paul Mackerras
2008-10-09 10:12 ` Dominik Bozek
2008-10-09 11:06 ` Paul Mackerras
2008-10-09 11:41 ` Dominik Bozek
2008-10-09 12:04 ` Leon Woestenberg
2008-10-09 15:37 ` Matt Sealey
2008-10-11 22:30 ` Benjamin Herrenschmidt
2008-10-12 2:05 ` Matt Sealey
2008-10-12 4:05 ` Benjamin Herrenschmidt
2008-10-13 15:20 ` Scott Wood
2008-10-13 20:50 ` Benjamin Herrenschmidt
2008-10-13 21:03 ` Scott Wood
2008-10-14 2:14 ` Matt Sealey
2008-10-14 2:39 ` Benjamin Herrenschmidt
2008-10-14 15:10 ` Scott Wood
2008-10-15 1:37 ` Matt Sealey
2008-10-10 17:17 ` Dominik Bozek
2008-10-08 17:40 ` Scott Wood
2008-10-09 2:36 ` Paul Mackerras
2008-10-11 22:32 ` Benjamin Herrenschmidt
2008-10-13 15:06 ` Scott Wood
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