linux-kernel - Re: Pipe buffers' limit of 16 * 4K

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Message-ID: <20080523205630.444fe2b9@bree.surriel.com>
Date:	Fri, 23 May 2008 20:56:30 -0400
From:	Rik van Riel <riel@...hat.com>
To:	"Fausto Richetti Blanco" <fausto.blanco@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Pipe buffers' limit of 16 * 4K

On Fri, 23 May 2008 21:19:13 -0300
"Fausto Richetti Blanco" <fausto.blanco@...il.com> wrote:

> Hello guys,
> 
>        I'm working with a 2.6.9 kernel (ok, I know it's quite old) and
> faced a problem with the 4K (one page) buffer limit for the pipes.
> I've found that in the 2.6.11 the pipes' buffers were changed to a
> circular list of pages which increased this limit to 16 * 4K. This
> limit is hardcoded here /usr/src/linux/include/linux/pipe_fs_i.h:6
> #define PIPE_BUFFERS (16)
> 
>        Is there a reason for this not to be an adjustable parameter
> (eg.: by an ulimit in the userspace) ?
 
What is the problem you found?

Why do you need to change the limit from 16?

Did it bring you any performance enhancements?

If so, how much?

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