* PIPE_SIZE aspects
@ 2009-05-22 9:39 Ad van den Broek
2009-05-23 19:54 ` Jens Axboe
0 siblings, 1 reply; 2+ messages in thread
From: Ad van den Broek @ 2009-05-22 9:39 UTC (permalink / raw
To: linux-kernel
I searched the net regarding PIPE_SIZE aspects.
This is what I found:
* The constant PIPE_SIZE
establishes the number of bytes allocated for a pipe
(the size of the pipe buffer)
* The default of PIPE_SIZE (in Linux 2.4) is PAGE_SIZE.
* The default of PIPE_SIZE (in Linux 2.6) is 64K.
* PAGE_SIZE (in Linux 2.4) is CPU/hw depending,
may not be changed and is 4K for x86.
* PAGE_SIZE (in Linux 2.6) is 64K.
* PIPE_SIZE can be changed in Linux 2.4,
but it should be NOT larger than PAGE_SIZE
or a patch should be implemented
I found a patch (I believe the author is Julian Bradfield) at
http://lse.sourceforge.net/pipe/2.4.9-pipe.patch
and this patch is modified by Manfred Spraul which version can be found at
http://linuxperf.sourceforge.net/patches/2.4.13-largepipe.patch
It is tested with PIPE_SIZE from 1 upto 2,4,8 pages.
and the result is at http://lse.sourceforge.net/pipe/pipe-report.txt
My questions:
Is the above info correct ?
Is the large pipe patch still correct for last 2.4.x versions ?
Is such a patch also required/possible in Linux 2.6
to allow PIPE_SIZE > PAGE_SIZE or is that different in 2.6 ?
--
With best regards,
Ad van den Broek
The Netherlands
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: PIPE_SIZE aspects
2009-05-22 9:39 PIPE_SIZE aspects Ad van den Broek
@ 2009-05-23 19:54 ` Jens Axboe
0 siblings, 0 replies; 2+ messages in thread
From: Jens Axboe @ 2009-05-23 19:54 UTC (permalink / raw
To: Ad van den Broek; +Cc: linux-kernel
On Fri, May 22 2009, Ad van den Broek wrote:
> I searched the net regarding PIPE_SIZE aspects.
> This is what I found:
>
> * The constant PIPE_SIZE
> establishes the number of bytes allocated for a pipe
> (the size of the pipe buffer)
>
> * The default of PIPE_SIZE (in Linux 2.4) is PAGE_SIZE.
> * The default of PIPE_SIZE (in Linux 2.6) is 64K.
>
> * PAGE_SIZE (in Linux 2.4) is CPU/hw depending,
> may not be changed and is 4K for x86.
> * PAGE_SIZE (in Linux 2.6) is 64K.
No changes for PAGE_SIZE, it's still hw dependent (and, one some archs,
dependent on kernel config).
> * PIPE_SIZE can be changed in Linux 2.4,
> but it should be NOT larger than PAGE_SIZE
> or a patch should be implemented
>
> I found a patch (I believe the author is Julian Bradfield) at
> http://lse.sourceforge.net/pipe/2.4.9-pipe.patch
> and this patch is modified by Manfred Spraul which version can be found at
> http://linuxperf.sourceforge.net/patches/2.4.13-largepipe.patch
> It is tested with PIPE_SIZE from 1 upto 2,4,8 pages.
> and the result is at http://lse.sourceforge.net/pipe/pipe-report.txt
>
>
> My questions:
> Is the above info correct ?
> Is the large pipe patch still correct for last 2.4.x versions ?
> Is such a patch also required/possible in Linux 2.6
> to allow PIPE_SIZE > PAGE_SIZE or is that different in 2.6 ?
2.6 uses an array of pages for the pipe. So while the x86 page size is
still 4kb, a pipe is by default 64kb because the array holds 16 pages.
I wrote a patch to set/get the pipe size for 2.6 if you are interested.
Find it here:
http://git.kernel.dk/?p=linux-2.6-block.git;a=commit;h=24547ac4d97bebb58caf9ce58bd507a95c812a3f
--
Jens Axboe
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2009-05-22 9:39 PIPE_SIZE aspects Ad van den Broek
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