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Re: unaligned access

To: Ralf Baechle <ralf@linux-mips.org>, "Kevin D. Kissell" <kevink@mips.com>
Subject: Re: unaligned access
From: sathesh babu <sathesh_edara2003@yahoo.co.in>
Date: Fri, 23 Feb 2007 09:48:38 +0000 (GMT)
Cc: sathesh babu <sathesh_edara2003@yahoo.co.in>, Rajat Jain <rajat.noida.india@gmail.com>, linux-mips@linux-mips.org
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It would be good idea to know which process hitting unaligned access and PC.
So that we can try to fix unaligned access when it causes the  performance bottleneck.
 
Could you please share details about logging the unaligned accesses using sysctl.
 
Thanks in advance
 
Regards,
Sathesh

Ralf Baechle <ralf@linux-mips.org> wrote:
On Thu, Feb 22, 2007 at 04:06:57PM +0100, Kevin D. Kissell wrote:

> Default behavior in MIPS is to silently fix up and emulate. A MIPS-specific
> system call (sys_sysmips with the command argument of MIPS_FIXADE
> and a parameter agument of zero) allows for this to be overridden, so that
> such accesses will be fatal. It looks as if there was once support to log the events
> to syslog, independently of whether or not they were fixed up, but it doesn't look to me
> as if that still works in 2.6.x kernels.

There used to be a configuration option to allow logging which was a
leftover from the times when I implemented the unaligned emulation. I
did never find it useful later on, so I removed that in almost 9 years
ago and nobody missed it since :-)

But I don't mind putting it back, controllable by sysctl if there is any
demand for it.

Ralf



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