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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <45EE503D.10608@zytor.com>
Date:	Tue, 06 Mar 2007 21:40:13 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Eric Dumazet <dada1@...mosbay.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 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
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/