From f125be1469303f7b9324447f251d74a0da24952f Mon Sep 17 00:00:00 2001
From: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Date: Mon, 18 Jan 2010 11:25:45 -0600
Subject: [PATCH] oprofile/x86: implement lsfr pseudo-random number generator
 for IBS

This patch implements a linear feedback shift register (LFSR) for
pseudo-random number generation for IBS.

For IBS measurements it would be good to minimize memory traffic in
the interrupt handler since every access pollutes the data
caches. Computing a maximal period LFSR just needs shifts and ORs.

The LFSR method is good enough to randomize the ops at low
overhead. 16 pseudo-random bits are enough for the implementation and
it doesn't matter that the pattern repeats with a fairly short
cycle. It only needs to break up (hard) periodic sampling behavior.

The logic was designed by Paul Drongowski.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>
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