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diff --git a/doc/html/TechNotes.html b/doc/html/TechNotes.html index 542d282..01f1a9a 100644 --- a/doc/html/TechNotes.html +++ b/doc/html/TechNotes.html @@ -237,6 +237,11 @@ HDF5 Technical Notes Results of reviewing tests for API functions. </td></tr> +<tr><td valign=top><a href="TechNotes/Basic_perform.html">Basic Performance Tools</a> + </td><td> </td><td valign=top> + A description of the three basic performance tools (chunk, iopipe, overhead). +</td></tr> + <tr><td valign=top><a href="TechNotes/VLTypes.html">Variable-Length Datatype Info</a> </td><td> </td><td valign=top> Description of various aspects of using variable-length datatypes in HDF5. @@ -286,7 +291,7 @@ HDF5 Technical Notes Describes HDF5 Release 1.6.0, July 2003 </address><!-- #EndLibraryItem --> -Last modified: 16 November 2002 +Last modified: 25 September 2003 </td> <td align=right valign=top> diff --git a/doc/html/TechNotes/Basic_perform.html b/doc/html/TechNotes/Basic_perform.html new file mode 100644 index 0000000..2a622fc --- /dev/null +++ b/doc/html/TechNotes/Basic_perform.html @@ -0,0 +1,75 @@ +<!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> |