Date: Sun, 17 Feb 2008 20:15:09 -0500 (EST)
From: Vince Weaver <vince@deater.net>
To: linux-kernel@vger.kernel.org
Subject: finding per-process hw interrupt counts
Message-ID: <Pine.LNX.4.64.0802171929480.5572@pianoman.cluster.toy>
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Hello

is there a way to find out how many times a userspace program is forced to 
context switch due to a hardware interrupt?

The reason for this:
I am measuring the retired instruction count of programs using performance 
counters (perfmon2 patchset), and trying to find out where the 
descrepancies compe from.

On x86, it seems to be:

   reported_count = expected_count + 1*major_pagefaults + \
                    1*hardware_interrupts + known_errata + 1

I can get the pagefault info from getrusage().  The hardware_interrupts 
count is my best guess at what is causing the rest, based on the LOC
field in /proc/interrupts.  That's not per-process though.

Is this info available?  If not, is it possible to patch the kernel to 
make it so?

Thanks for any help

Vince
vince@deater.net
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