From: george anzinger <george@mvista.com>
To: Andrew Morton <akpm@osdl.org>
Cc: bernie@develer.com, linux-kernel@vger.kernel.org,
rmk@arm.linux.org.uk, torvalds@osdl.org
Subject: Re: do_div64 generic
Date: Tue, 15 Jul 2003 17:07:35 -0700 [thread overview]
Message-ID: <3F149747.3090107@mvista.com> (raw)
In-Reply-To: <20030715150645.4fa11de7.akpm@osdl.org>
Andrew Morton wrote:
> george anzinger <george@mvista.com> wrote:
>
>>>George, do you agree? May I go on and post a patch killing
>>>div_long_long_rem() everywhere?
>>
>>The issue is that div is a very long instruction and the do_div()
>>thing uses 2 or three of them, while the div_long_long_rem() is just
>>1. Also, a lot of archs already have the required div by a different
>>name. It all boils down to a performance thing.
>
>
> It is only used in nanosleep(), and then only in the case where the sleep
> terminated early.
>
> If someone is calling nanosleep() so frequently for this to matter, the
> time spent in divide is the least of their problems. Unless you have some
> real-worldish benchmarks to demonstrate otherwise?
It is also used in the jiffies to timespec and jiffies to timeval code
in timer.h, if memory serves.
>
> You know what they say about premtur optmstns, and having to propagate
> funky new divide primitives across N architectures is indeed evil.
Hm. I only want the simple div. 64-bit/32-bit in two 32-bit results.
Is this funky? And the "evil" #ifdef allows archs to not do it.
>
> Bernardo, can you do the patch please?
>
>
--
George Anzinger george@mvista.com
High-res-timers: http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml
next prev parent reply other threads:[~2003-07-15 23:53 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <3F1360F4.2040602@mvista.com>
2003-07-15 5:17 ` do_div64 generic Bernardo Innocenti
2003-07-15 5:38 ` Andrew Morton
2003-07-15 6:23 ` Bernardo Innocenti
2003-07-15 6:30 ` Andrew Morton
2003-07-15 21:52 ` george anzinger
2003-07-15 22:06 ` Andrew Morton
2003-07-16 0:07 ` george anzinger [this message]
2003-07-16 18:33 ` Bernardo Innocenti
2003-07-17 21:10 ` Bernardo Innocenti
2003-07-17 21:16 ` Andrew Morton
2003-07-17 22:43 ` Bernardo Innocenti
2003-07-17 23:10 ` george anzinger
2003-07-18 3:19 ` Andrew Morton
2003-07-18 4:14 ` Bernardo Innocenti
2003-07-17 23:09 ` george anzinger
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