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From: Paul Marquis <pmarquis@iname.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Date: Thu, 02 Nov 2000 18:44:05 -0500
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Subject: Re: select() bug
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Okay, I see your point, thanks.  A couple of comments/questions:

- Does this make sense with devices with small kernel buffers?  From
my experimentation, pipes on Linux have a 4K buffer and tend to be
read and written very quickly.

- If I'm correct that pipes have a 4K kernel buffer, then writing 1
byte shouldn't cause this situation, as the buffer is well more than
half empty.  Is this still a bug?

Semantic issues aside, since Apache does the test I mentionned earlier
to determine child status and since it could be misled, should this
feature be turned off?

Thanks for your input.

Alan Cox wrote:
> > I'm not exactly sure what you mean by this statement.  Would you mind
> > explaining further?
> 
> Well take a socket with 64K of buffering. You don't want to wake processes
> waiting in select or in write every time you can scribble another 1460 bytes
> to the buffer. Instead you wait until there is 32K of room then wake the
> user. That means that there is one wakeup/trip through userspace every 32K
> rather than potentially every time a byte is read the other end

-- 
Paul Marquis
pmarquis@iname.com

If it's tourist season, why can't we shoot them?
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