mirror of
https://github.com/HDFGroup/hdf5.git
synced 2025-02-17 16:10:24 +08:00
0f70e6ea7e
Added the entry of document of the three basic performance tools. The information was provided by Robb long time ago. Platforms tested: Viewed by IE. Misc. update:
76 lines
2.8 KiB
HTML
76 lines
2.8 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
|
|
<html>
|
|
<head>
|
|
<title>Description of the three basic performance tools</title>
|
|
</head>
|
|
|
|
<body>
|
|
<h1>Description of the three basic performance tools</h1>
|
|
|
|
<h2>iopipe</h2>
|
|
<p>Times reads and writes to an HDF5 2-d dataset and compares that with
|
|
reads and writes using POSIX I/O. Reports seven measurements in
|
|
terms of CPU user time, CPU system time, elapsed time, and
|
|
bandwidth:
|
|
|
|
|
|
<DL>
|
|
<DD>fill raw: time it takes to memset() a buffer.</DD>
|
|
<DD> fill hdf5: time it takes to read from a dataset never written</DD>
|
|
<DD>out raw: time it takes to write using POSIX I/O</DD>
|
|
<DD>out hdf5: time it takes to write using H5Dwrite()</DD>
|
|
<DD>in raw: time it takes to read data just written using POSIX I/O</DD>
|
|
<DD>in hdf5: time it takes to H5Dread() data written with H5Dwrite()</DD>
|
|
<DD>in hdf5 partial: time it takes to H5Dread() the "center" area.</DD>
|
|
</DL>
|
|
|
|
|
|
<p>This is a pretty stupid performance test. It accesses the same area
|
|
of file and memory over and over and the file size is way too
|
|
small. But it is good at showing how much overhead there is in the
|
|
library itself.
|
|
|
|
|
|
<h2>chunk</h2>
|
|
<p>Determines how efficient the raw data cache is for various access
|
|
patterns of a chunked dataset, both reading and writing. The access
|
|
pattern is either (a) we access the entire dataset by moving a window
|
|
across and down a 2-d dataset in row-major order a full window
|
|
height and width at a time, or (b) we access part of a dataset by moving
|
|
the window diagonally from the (0,0) corner to the opposite corner
|
|
by half the window height and width at a time. The window is
|
|
measured in terms of the chunk size.
|
|
|
|
|
|
<p>The result is:
|
|
<br>A table written to stdout that contains the window size as a
|
|
fraction of the chunk size and the efficiencey of the cache (i.e.,
|
|
number of bytes accessed by H5Dread() or H5Dwrite() divided by the
|
|
number of bytes of the dataset actually read or written by lower
|
|
layers.
|
|
|
|
|
|
<p>A gnuplot script and data files which can be displayed by running
|
|
gnuplot and typing the command `load "x-gnuplot"'.
|
|
|
|
|
|
<h2>overhead</h2>
|
|
<p>Measures the overhead used by the B-tree for indexing chunked
|
|
datasets. As data is written to a chunked dataset the B-tree
|
|
grows and its nodes get split. When a node splits one of three
|
|
ratios are used to determine how many items from the original node
|
|
go into the new left and right nodes, and these ratios affect the
|
|
total size of the B-tree in a way that depends on the order that
|
|
data is written to the dataset.
|
|
|
|
|
|
<p>Invoke as `overhead usage' for more information.
|
|
<hr>
|
|
<address><a href="mailto:matzke@llnl.gov">Robb Matzke</a></address>
|
|
<!-- Created: Tue Mar 17 11:13:35 EST 1998 -->
|
|
<!-- hhmts start -->
|
|
Last modified: Jun 4, 2003
|
|
<!-- hhmts end -->
|
|
</body>
|
|
</html>
|