From: Timothy Miller <miller@techsource.com>
To: Daniel Forrest <forrest@lmcg.wisc.edu>
Cc: Peter Kjellerstedt <peter.kjellerstedt@axis.com>,
"'Willy Tarreau'" <willy@w.ods.org>,
linux-kernel mailing list <linux-kernel@vger.kernel.org>
Subject: Re: generic strncpy - off-by-one error
Date: Mon, 18 Aug 2003 12:17:06 -0400 [thread overview]
Message-ID: <3F40FC02.3000506@techsource.com> (raw)
In-Reply-To: 20030816034129.A6301@rda07.lmcg.wisc.edu
Daniel Forrest wrote:
> On Sat, Aug 16, 2003 at 10:15:14AM +0200, Peter Kjellerstedt wrote:
> Shouldn't this be:
>
> while (tmp & (sizeof(long) - 1)) {
>
>
>> *tmp++ = '\0';
>> count--;
>> }
Oh, yeah! That's right. We need to check the address. Also need to
cast tmp to (int) or something (doesn't matter what it's cast to,
because we only care about the lower 2 or 3 bits).
Peter, please see if this makes any speed difference. But it definately
needs this fix.
Frankly, I'm surprised it works. In fact, it might not, but it's hard
to tell from the tests just benchmarks.
Also, if you're doing dense addressing on Alpha, and you do byte
accesses the addresses for char are byte addresses, but the code does
read-modify-write to memory for byte accesses, because in that mode, you
can only do 32-bit and 64-bit accesses. The performance increase could
be even greater for Alpha than for x86.
For Sparc, we might be able to do something with VIS instructions,
although I don't know what the setup overhead is. Sun's memcpy and
memset only use VIS when the size is greater than 512, because
otherwise, it's not worth it.
I don't know enough about PowerPC other than the proper use of the
"eieio" instruction. :)
next prev parent reply other threads:[~2003-08-18 16:01 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-08-16 8:15 generic strncpy - off-by-one error Peter Kjellerstedt
2003-08-16 8:41 ` Daniel Forrest
2003-08-18 16:17 ` Timothy Miller [this message]
2003-08-18 16:06 ` Timothy Miller
-- strict thread matches above, loose matches on Subject: below --
2003-08-20 7:43 Peter Kjellerstedt
2003-08-16 21:10 Peter Kjellerstedt
2003-08-18 18:41 ` Timothy Miller
2003-08-16 20:08 Peter Kjellerstedt
2003-08-16 9:19 Peter Kjellerstedt
2003-08-16 10:04 ` Daniel Forrest
2003-08-18 16:40 ` Timothy Miller
2003-08-15 9:54 Peter Kjellerstedt
2003-08-15 17:52 ` Timothy Miller
2003-08-15 9:53 Peter Kjellerstedt
2003-08-15 17:47 ` Timothy Miller
2003-08-14 9:34 Peter Kjellerstedt
2003-08-14 19:45 ` Willy Tarreau
2003-08-14 20:24 ` Timothy Miller
2003-08-13 3:09 Anthony Truong
2003-08-13 2:18 Albert Cahalan
2003-08-13 2:47 ` Erik Andersen
2003-08-13 3:38 ` Albert Cahalan
2003-08-13 3:56 ` Nick Piggin
2003-08-13 5:18 ` Willy Tarreau
2003-08-13 19:03 ` Timothy Miller
2003-08-12 14:07 Yoshinori Sato
2003-08-12 14:39 ` Willy Tarreau
2003-08-12 14:50 ` Yoshinori Sato
2003-08-12 15:03 ` Valdis.Kletnieks
2003-08-12 15:54 ` William Gallafent
2003-08-12 16:19 ` Valdis.Kletnieks
2003-08-12 16:09 ` Andreas Schwab
2003-08-12 1:56 Anthony Truong
2003-08-12 17:14 ` Alan Cox
2003-08-12 21:53 ` Bernd Petrovitsch
2003-08-12 1:28 Anthony Truong
2003-08-12 16:24 ` Bernd Petrovitsch
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