linux-kernel - Re: [patch v2] epoll use a single inode ...

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Date:	Wed, 07 Mar 2007 07:57:14 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch v2] epoll use a single inode ...

Linus Torvalds a écrit :
> 
> 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.

And the numbers were ? :)

> 
> (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)

Well, given that sprintf() is frequently called only for pipe/sockets 
creation, we probably better :

1) wait a very clever idea to suppress individual dentry per pipe/sockets (no 
more sprintf() at pipe/socket setup)

2) delay the sprintf() only if needed as you mentioned in a previous mail 
(when someone wants ls -l /proc/pid/fd/....), since their dentries are not 
anymore inserted in the global dcache hash, they could stay with a (nul) dname.


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