tree 442153e96f6261a7fed4e7a1dfdcfa7f787097d7
parent ab620aca1b6946bd2978d67103b0734e5dfd475d
author Andreas Sandberg <andreas.sandberg@arm.com> 1461360416 +0100
committer Andreas Sandberg <andreas.sandberg@arm.com> 1567080745 +0000

stats: Add beta support for HDF5 stat dumps

This changeset add support for stat dumps in the HDF5 file
format. HDF5 is a binary data format that represents data in a
file-system-like balanced tree. It has native support for
N-dimensional arrays and binary data (e.g., frame buffers).

It has the following benefits over traditional text stat files:

  * Efficient storage of time series (multiple stat dumps)

  * Fast lookup of stats

  * Plenty of existing tooling (e.g., Python libraries and graphical
    viewers)

  * File format can be used to store frame buffers together with
    normal stats.

Drawbacks:

  * Large startup cost (single stat dump larger than text equivalent)

  * Stat dumps are slower than text

Known limitations:

  * Distributions and histograms aren't supported.

HDF5 stat output can be enabled using the 'h5' URL scheme when
overriding the stat file name on gem5's command line. The following
parameters are supported:

  * chunking (unsigned): Number of time steps to pre-allocate
    (default: 10)

  * desc (bool): Output stat descriptions (default: True)

  * formulas (bool): Output derived stats (default: True)

Example gem5 command line:

./build/ARM/gem5.opt \
  --stats-file="h5://stats.h5?desc=False;formulas=False" \
  configs/example/fs.py

Example Python stat consumer that computes IPC:
  import h5py

  f = h5py.File('stats.h5', 'r')
  group = f['/system/cpu']
  for i, c in zip(group['committedInsts'], group['numCycles']):
      print i, c, i / c

Change-Id: I351c6cbff2fb7bef9012f47876ba227ed288975b
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/8121
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Ciro Santilli <ciro.santilli@arm.com>