From: "H. Peter Anvin" <hpa@zytor.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Dumazet <dada1@cosmosbay.com>,
Davide Libenzi <davidel@xmailserver.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [patch v2] epoll use a single inode ...
Date: Tue, 06 Mar 2007 21:40:13 -0800 [thread overview]
Message-ID: <45EE503D.10608@zytor.com> (raw)
In-Reply-To: <Pine.LNX.4.64.0703061944590.5963@woody.linux-foundation.org>
Linus Torvalds wrote:
>
> On Tue, 6 Mar 2007, Eric Dumazet wrote:
>> I did a user space program, attached to this mail.
>>
>> I rewrote the reciprocal_div() for i386 so that one multiply is used.
>
> Ok, this is definitely faster on Core 2 as well, so "numbers talk,
> bullshit walks". No more objections.
>
> (That said, I bet you could do even better for octal and hex numbers, so
> if you *really* want to speed things up, you should just make a
> special-case routine for each base (there's just three of them), and you
> can then also optimize the base-10 thing much better (you can do two
> digits at a time by dividing by 100, etc)
>
Of course you can do better for octal and hex -- it's just shift and mask.
Decimal is trickier; however, at least on i386 it might make sense to
divide by 100 and then use the AAM instruction, or a table lookup, to
split it into individual digits.
-hpa
next prev parent reply other threads:[~2007-03-07 5:40 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-05 23:41 [patch v2] epoll use a single inode Davide Libenzi
2007-03-06 0:00 ` Linus Torvalds
2007-03-06 0:12 ` Davide Libenzi
2007-03-06 0:20 ` Davide Libenzi
2007-03-06 0:25 ` Linus Torvalds
2007-03-06 2:25 ` H. Peter Anvin
2007-03-06 2:34 ` Davide Libenzi
2007-03-06 2:37 ` H. Peter Anvin
2007-03-06 2:43 ` Davide Libenzi
2007-03-06 6:22 ` Eric Dumazet
2007-03-06 6:31 ` Davide Libenzi
2007-03-06 6:37 ` Davide Libenzi
2007-03-06 16:28 ` H. Peter Anvin
2007-03-06 17:09 ` Linus Torvalds
2007-03-06 17:14 ` H. Peter Anvin
2007-03-06 17:12 ` Eric Dumazet
2007-03-06 17:19 ` Linus Torvalds
2007-03-06 17:27 ` H. Peter Anvin
2007-03-06 17:28 ` Eric Dumazet
2007-03-06 18:10 ` Eric Dumazet
2007-03-06 20:20 ` Eric Dumazet
2007-03-07 3:47 ` Linus Torvalds
2007-03-07 5:40 ` H. Peter Anvin [this message]
2007-03-07 6:57 ` Eric Dumazet
2007-03-07 7:13 ` H. Peter Anvin
2007-03-07 23:46 ` Sami Farin
2007-03-06 18:10 ` Davide Libenzi
2007-03-10 8:06 ` Pavel Machek
2007-03-10 8:24 ` Davide Libenzi
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