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diff --git a/doc/html/TechNotes/FreeLists.html b/doc/html/TechNotes/FreeLists.html deleted file mode 100644 index 1a4b8e8..0000000 --- a/doc/html/TechNotes/FreeLists.html +++ /dev/null @@ -1,205 +0,0 @@ -<html> -<head> -<title>Memory Management and Free Lists</title> -</head> - -<body> - -<h1>Memory Management and Free Lists</h1> - -<pre> - -At Release 1.2.2, free list management code was introduced to the HDF5 -library. This included one user-level function, H5garbage_collect, which -garbage collects on all the free-lists. H5garbage_collect is the only user- -accessible (i.e., application developer-accessible) element of this -functionality. - -The free-lists generally reduce the amount of dynamic memory used to around -75% of the pre-optimized amount as well as speed up the time in the library -code by ~5% The free-lists also help linearize the amount of memory used with -increasing numbers of datasets or re-writes on the data, so the amount of -memory used for the 1500/45 free-list case is only 66% of the memory used for -the unoptimized case. - -Overall, the introduction of free list management is a win: the library is -slightly faster and uses much less system resources than before. Most of the -emphasis has been focused on the main "thouroughfares" through the code; -less attention was paid to the "back streets" which are used much less -frequently and offer less potential for abuse. - -Adding a free-list for a data structure in the HDF5 library code is easy: - -Old code: ---------- - int foo(void) - { - H5W_t *w; - - for(i=0; i<x; i++) { - w=H5MM_malloc(sizeof(H5W_t)); - <use w> - H5MM_xfree(w); - } - } - -New code: ---------- -H5FL_DEFINE(H5W_t); - - int foo(void) - { - H5W_t *w; - - for(i=0; i<x; i++) { - w=H5FL_ALLOC(H5W_t,0); - <use w> - H5FL_FREE(H5W_t,w); - } - } - - -There are three kinds of free-lists: - -- for "regular" objects, - -- arrays of fixed size object (both fixed length and unknown length), and - -- "blocks" of bytes. - - "Regular" free-lists use the H5FL_<*> macros in H5FLprivate.h and are - designed for single, fixed-size data structures like typedef'ed structs, - etc. - - Arrays of objects use the H5FL_ARR_<*> macros and are designed for arrays - (both fixed in length and varying lengths) of fixed length data structures - (like typedef'ed types). - - "Block" free-lists use the H5FL_BLK_<*> macros and are designed to hold - varying sized buffers of bytes, with no structure. - - H5S.c contains examples for "regular" and fixed-sized arrays; - H5B.c contains examples for variable-sized arrays and "blocks". - -A free-list doesn't have to be used for every data structure allocated and -freed, just for those which are prone to abuse when multiple operations are -being performed. It is important to use the macros for declaring and -manipulating the free-lists however; they allow the free'd objects on the -lists to be garbage collected by the library at the library's termination -or at the user's request. - -One public API function has been added: H5garbage_collect, which garbage -collects on all the free-lists of all the different types. It's not required -to be called and is only necessary in situations when the application -performs actions which cause the library to allocate many objects and then -the application eventually releases those objects and wants to reduce the -memory used by the library from the peak usage required. The library -automatically garbage collects all the free lists when the application ends. - -Questions should be sent to the HDF Help Desk at hdfhelp@ncsa.uiuc.edu. - - -=========================================== -BENCHMARK INFORMATION -=========================================== - -New version with free lists: - -Datasets=500, Data Rewrites=15: - Peak Heap Usage: 18210820 bytes - Time in library code: 2.260 seconds - # of malloc calls: 22864 - -Datasets=1000, Data Rewrites=15: - Peak Heap Usage: 31932420 bytes - Time in library code: 5.090 seconds - # of malloc calls: 43045 - -Datasets=1500, Data Rewrites=15: - Peak Heap Usage: 41566212 bytes - Time in library code: 8.623 seconds - # of malloc calls: 60623 - -Datasets=500, Data Rewrites=30: - Peak Heap Usage: 19456004 bytes - Time in library code: 4.274 seconds - # of malloc calls: 23353 - -Datasets=1000, Data Rewrites=30: - Peak Heap Usage: 33988612 bytes - Time in library code: 9.955 seconds - # of malloc calls: 43855 - -Datasets=1500, Data Rewrites=30: - Peak Heap Usage: 43950084 bytes - Time in library code: 17.413 seconds - # of malloc calls: 61554 - -Datasets=500, Data Rewrites=45: - Peak Heap Usage: 20717572 bytes - Time in library code: 6.326 seconds - # of malloc calls: 23848 - -Datasets=1000, Data Rewrites=45: - Peak Heap Usage: 35807236 bytes - Time in library code: 15.146 seconds - # of malloc calls: 44572 - -Datasets=1500, Data Rewrites=45: - Peak Heap Usage: 46022660 bytes - Time in library code: 27.140 seconds - # of malloc calls: 62370 - - -Older version with no free lists: - -Datasets=500, Data Rewrites=15: - Peak Heap Usage: 25370628 bytes - Time in library code: 2.329 seconds - # of malloc calls: 194991 - -Datasets=1000, Data Rewrites=15: - Peak Heap Usage: 39550980 bytes - Time in library code: 5.251 seconds - # of malloc calls: 417971 - -Datasets=1500, Data Rewrites=15: - Peak Heap Usage: 68870148 bytes - Time in library code: 8.913 seconds - # of malloc calls: 676564 - -Datasets=500, Data Rewrites=30: - Peak Heap Usage: 31670276 bytes - Time in library code: 4.435 seconds - # of malloc calls: 370320 - -Datasets=1000, Data Rewrites=30: - Peak Heap Usage: 44646404 bytes - Time in library code: 10.325 seconds - # of malloc calls: 797125 - -Datasets=1500, Data Rewrites=30: - Peak Heap Usage: 68870148 bytes - Time in library code: 18.057 seconds - # of malloc calls: 1295336 - -Datasets=500, Data Rewrites=45: - Peak Heap Usage: 33906692 bytes - Time in library code: 6.577 seconds - # of malloc calls: 545656 - -Datasets=1000, Data Rewrites=45: - Peak Heap Usage: 56778756 bytes - Time in library code: 15.720 seconds - # of malloc calls: 1176285 - -Datasets=1500, Data Rewrites=45: - Peak Heap Usage: 68870148 bytes - Time in library code: 28.138 seconds - # of malloc calls: 1914097 - - -=========================================== -Last Modified: 3 May 2000 -HDF Help Desk: hdfhelp@ncsa.uiuc.edu - -</pre> -</body> -</html> |