configs: Use absolute import paths

Use absoluate import paths to be Python 3 compatible. This also
imports absolute_import from __future__ to ensure that Python 2.7
behaves the same way as Python 3.

Change-Id: Ica06ed95814e9cd3e768b3e1785075e36f6e56d0
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/16708
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

configs: fixed SimpleOpts missing error by adding library path

Change-Id: I0de761c8a322a506e436d5c7f12ee509535f52fd
Reviewed-on: https://gem5-review.googlesource.com/2801
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

mem: Split the hit_latency into tag_latency and data_latency

If the cache access mode is parallel, i.e. "sequential_access" parameter
is set to "False", tags and data are accessed in parallel. Therefore,
the hit_latency is the maximum latency between tag_latency and
data_latency. On the other hand, if the cache access mode is
sequential, i.e. "sequential_access" parameter is set to "True",
tags and data are accessed sequentially. Therefore, the hit_latency
is the sum of tag_latency plus data_latency.

Signed-off-by: Jason Lowe-Power <jason@lowepower.com>

config: Make configs/common a Python package

Continue along the same line as the recent patch that made the
Ruby-related config scripts Python packages and make also the
configs/common directory a package.

All affected config scripts are updated (hopefully).

Note that this change makes it apparent that the current organisation
and naming of the config directory and its subdirectories is rather
chaotic. We mix scripts that are directly invoked with scripts that
merely contain convenience functions. While it is not addressed in
this patch we should follow up with a re-organisation of the
config structure, and renaming of some of the packages.

config: Add configs scripts used in Learning gem5

Added a new directory in configs (learning_gem5) to hold the scripts that are
used in the book. See http://lowepower.com/jason/learning_gem5/ for a working
copy. For now, only the scripts in Part 1: Getting started with gem5
have been added. A separate patch adds tests for these scripts.

Committed by: Nilay Vaish <nilay@cs.wisc.edu>