From: "H. Peter Anvin" <hpa@zytor.com>
To: Eric Dumazet <dada1@cosmosbay.com>
Cc: Davide Libenzi <davidel@xmailserver.org>,
Linus Torvalds <torvalds@linux-foundation.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 08:28:22 -0800 [thread overview]
Message-ID: <45ED96A6.3000704@zytor.com> (raw)
In-Reply-To: <45ED08A9.9050501@cosmosbay.com>
Eric Dumazet wrote:
>
> For epoll, I suspect this is harmless : Programs dont allocate epolls fd
> every milli second, but at startup only.
>
> For pipes/sockets, using a 64 bits would be problematic, because
> sprintf() uses a divide for each digit. And a divide is slow. Ten
> divides are *very* slow.
>
That's true for *any* sprintf(), though. sprintf() converts all its
arguments to 64 bits.
However, this could be optimized. I think right now sprintf() uses a
generic divide-by-base, but a divide by 8 and 16 can of course be
handled with a shift, and divide by 10 can be replaced with a
multiplication by 0x1999999999999999ULL on most architectures.
-hpa
next prev parent reply other threads:[~2007-03-06 16:28 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 [this message]
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
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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