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

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Message-ID: <Pine.LNX.4.64.0703051621590.3998@woody.linux-foundation.org>
Date:	Mon, 5 Mar 2007 16:25:36 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Davide Libenzi <davidel@...ilserver.org>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Eric Dumazet <dada1@...mosbay.com>
Subject: Re: [patch v2] epoll use a single inode ...

On Mon, 5 Mar 2007, Davide Libenzi wrote:

> On Mon, 5 Mar 2007, Linus Torvalds wrote:
> > 
> > It's much better to do something like
> > 
> > 	static unsigned int epoll_inode;
> > 
> > 	this.len = sprintf(name, "[%u]", ++epoll_inode);
> > 
> > if you just need some pseudo-unique name to distinguish two epoll things 
> > from each other (vs from a dup'ed fd).
> 
> Heh, this is what Al was saying ;)
> I'm fine with that, but how about counter cycles (going back to zero)? 
> Should we care to handle them correctly? 

Since this is not actually *used* for anything but showing the fd's in 
/proc/<pid>/fd/ etc, no. In fact, an integer will wrap a *lot* less than a 
kernel data structure will be re-used, so even with the simple "wraps 
every 4G uses", you're still better off.

IOW, if the thing actually _mattered_ we should use some bitmap allocator 
or similar (eg pidmaps etc), but with something where the only reason 
really is as a visible indicator of difference for a user that happens to 
look, simple-and-stupid is better.

		Linus
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