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| author | Frank Baker <fbaker@hdfgroup.org> | 2005-07-19 17:28:56 (GMT) |
|---|---|---|
| committer | Frank Baker <fbaker@hdfgroup.org> | 2005-07-19 17:28:56 (GMT) |
| commit | 794ba0a251af47b8e3c60afa2fe92d267e2a6b55 (patch) | |
| tree | f24cea3b81ff02fa3f31c0a1c4e80fa10f4393c0 /doc/html/Caching.html | |
| parent | d2e92fd23610c3ccdddbbc55484e54a5a21a9252 (diff) | |
| download | hdf5-794ba0a251af47b8e3c60afa2fe92d267e2a6b55.zip hdf5-794ba0a251af47b8e3c60afa2fe92d267e2a6b55.tar.gz hdf5-794ba0a251af47b8e3c60afa2fe92d267e2a6b55.tar.bz2 | |
[svn-r11084]
Description:
All HDF5 user documentation has been moved to a separate hdf5doc/
repository, managed under Subversion.
With this 'cvs commit', all files are stripped from hdf5/doc/.
THIS CHANGE IS APPLIED ONLY TO THE HDF5 DEVELOPMENT BRANCH,
post Release 1.6.x; it is not applied to the release branches.
Diffstat (limited to 'doc/html/Caching.html')
| -rw-r--r-- | doc/html/Caching.html | 190 |
1 files changed, 0 insertions, 190 deletions
diff --git a/doc/html/Caching.html b/doc/html/Caching.html deleted file mode 100644 index d194ba3..0000000 --- a/doc/html/Caching.html +++ /dev/null @@ -1,190 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN"> -<html> - <head> - <title>Data Caching</title> - -<!-- #BeginLibraryItem "/ed_libs/styles_UG.lbi" --> -<!-- - * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * - * Copyright by the Board of Trustees of the University of Illinois. * - * All rights reserved. * - * * - * This file is part of HDF5. The full HDF5 copyright notice, including * - * terms governing use, modification, and redistribution, is contained in * - * the files COPYING and Copyright.html. COPYING can be found at the root * - * of the source code distribution tree; Copyright.html can be found at the * - * root level of an installed copy of the electronic HDF5 document set and * - * is linked from the top-level documents page. It can also be found at * - * http://hdf.ncsa.uiuc.edu/HDF5/doc/Copyright.html. If you do not have * - * access to either file, you may request a copy from hdfhelp@ncsa.uiuc.edu. * - * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * - --> - -<link href="ed_styles/UGelect.css" rel="stylesheet" type="text/css"> -<!-- #EndLibraryItem --></head> - - <body bgcolor="#FFFFFF"> - - -<!-- #BeginLibraryItem "/ed_libs/NavBar_UG.lbi" --><hr> -<center> -<table border=0 width=98%> -<tr><td valign=top align=left> - <a href="index.html">HDF5 documents and links</a> <br> - <a href="H5.intro.html">Introduction to HDF5</a> <br> - <a href="RM_H5Front.html">HDF5 Reference Manual</a> <br> - <a href="http://hdf.ncsa.uiuc.edu/HDF5/doc/UG/index.html">HDF5 User's Guide for Release 1.6</a> <br> - <!-- - <a href="Glossary.html">Glossary</a><br> - --> -</td> -<td valign=top align=right> - And in this document, the - <a href="H5.user.html"><strong>HDF5 User's Guide from Release 1.4.5:</strong></a> - <br> - <a href="Files.html">Files</a> - <a href="Datasets.html">Datasets</a> - <a href="Datatypes.html">Datatypes</a> - <a href="Dataspaces.html">Dataspaces</a> - <a href="Groups.html">Groups</a> - <br> - <a href="References.html">References</a> - <a href="Attributes.html">Attributes</a> - <a href="Properties.html">Property Lists</a> - <a href="Errors.html">Error Handling</a> - <br> - <a href="Filters.html">Filters</a> - <a href="Caching.html">Caching</a> - <a href="Chunking.html">Chunking</a> - <a href="MountingFiles.html">Mounting Files</a> - <br> - <a href="Performance.html">Performance</a> - <a href="Debugging.html">Debugging</a> - <a href="Environment.html">Environment</a> - <a href="ddl.html">DDL</a> -</td></tr> -</table> -</center> -<hr> -<!-- #EndLibraryItem --><h1>Data Caching</h1> - - <h2>1. Meta Data Caching</h2> - - <p>The HDF5 library caches two types of data: meta data and raw - data. The meta data cache holds file objects like the file - header, symbol table nodes, global heap collections, object - headers and their messages, etc. in a partially decoded - state. The cache has a fixed number of entries which is set with - the file access property list (defaults to 10k) and each entry - can hold a single meta data object. Collisions between objects - are handled by preempting the older object in favor of the new - one. - - <h2>2. Raw Data Chunk Caching</h2> - - <p>Raw data chunks are cached because I/O requests at the - application level typically don't map well to chunks at the - storage level. The chunk cache has a maximum size in bytes - set with the file access property list (defaults to 1MB) and - when the limit is reached chunks are preempted based on the - following set of heuristics. - - <ul> - <li>Chunks which have not been accessed for a long time - relative to other chunks are penalized. - <li>Chunks which have been accessed frequently in the recent - past are favored. - <li>Chunks which are completely read and not written, completely - written but not read, or completely read and completely - written are penalized according to <em>w0</em>, an - application-defined weight between 0 and 1 inclusive. A weight - of zero does not penalize such chunks while a weight of 1 - penalizes those chunks more than all other chunks. The - default is 0.75. - <li>Chunks which are larger than the maximum cache size do not - participate in the cache. - </ul> - - <p>One should choose large values for <em>w0</em> if I/O requests - typically do not overlap but smaller values for <em>w0</em> if - the requests do overlap. For instance, reading an entire 2d - array by reading from non-overlapping "windows" in a row-major - order would benefit from a high <em>w0</em> value while reading - a diagonal accross the dataset where each request overlaps the - previous request would benefit from a small <em>w0</em>. - - <h2>3. Data Caching Operations</h2> - - <p>The cache parameters for both caches are part of a file access - property list and are set and queried with this pair of - functions: - - <dl> - <dt><code>herr_t H5Pset_cache(hid_t <em>plist</em>, unsigned int - <em>mdc_nelmts</em>, size_t <em>rdcc_nbytes</em>, double - <em>w0</em>)</code> - <dt><code>herr_t H5Pget_cache(hid_t <em>plist</em>, unsigned int - *<em>mdc_nelmts</em>, size_t *<em>rdcc_nbytes</em>, double - <em>w0</em>)</code> - <dd>Sets or queries the meta data cache and raw data chunk cache - parameters. The <em>plist</em> is a file access property - list. The number of elements (objects) in the meta data cache - is <em>mdc_nelmts</em>. The total size of the raw data chunk - cache and the preemption policy is <em>rdcc_nbytes</em> and - <em>w0</em>. For <code>H5Pget_cache()</code> any (or all) of - the pointer arguments may be null pointers. - </dl> - - -<!-- #BeginLibraryItem "/ed_libs/NavBar_UG.lbi" --><hr> -<center> -<table border=0 width=98%> -<tr><td valign=top align=left> - <a href="index.html">HDF5 documents and links</a> <br> - <a href="H5.intro.html">Introduction to HDF5</a> <br> - <a href="RM_H5Front.html">HDF5 Reference Manual</a> <br> - <a href="http://hdf.ncsa.uiuc.edu/HDF5/doc/UG/index.html">HDF5 User's Guide for Release 1.6</a> <br> - <!-- - <a href="Glossary.html">Glossary</a><br> - --> -</td> -<td valign=top align=right> - And in this document, the - <a href="H5.user.html"><strong>HDF5 User's Guide from Release 1.4.5:</strong></a> - <br> - <a href="Files.html">Files</a> - <a href="Datasets.html">Datasets</a> - <a href="Datatypes.html">Datatypes</a> - <a href="Dataspaces.html">Dataspaces</a> - <a href="Groups.html">Groups</a> - <br> - <a href="References.html">References</a> - <a href="Attributes.html">Attributes</a> - <a href="Properties.html">Property Lists</a> - <a href="Errors.html">Error Handling</a> - <br> - <a href="Filters.html">Filters</a> - <a href="Caching.html">Caching</a> - <a href="Chunking.html">Chunking</a> - <a href="MountingFiles.html">Mounting Files</a> - <br> - <a href="Performance.html">Performance</a> - <a href="Debugging.html">Debugging</a> - <a href="Environment.html">Environment</a> - <a href="ddl.html">DDL</a> -</td></tr> -</table> -</center> -<hr> -<!-- #EndLibraryItem --><!-- #BeginLibraryItem "/ed_libs/Footer.lbi" --><address> -<a href="mailto:hdfhelp@ncsa.uiuc.edu">HDF Help Desk</a> -<br> -Describes HDF5 Release 1.4.5, February 2003 -</address><!-- #EndLibraryItem --><!-- Created: Tue May 26 15:20:14 EDT 1998 --> -<!-- hhmts start --> -Last modified: 13 December 1999 -<!-- hhmts end --> - - -</body> -</html> |