diff options
Diffstat (limited to 'src/H5ACpublic.h')
| -rw-r--r-- | src/H5ACpublic.h | 61 |
1 files changed, 60 insertions, 1 deletions
diff --git a/src/H5ACpublic.h b/src/H5ACpublic.h index 0ddef92..0e75117 100644 --- a/src/H5ACpublic.h +++ b/src/H5ACpublic.h @@ -15,7 +15,7 @@ /*------------------------------------------------------------------------- * - * Created: H5ACproto.h + * Created: H5ACpublic.h * Jul 10 1997 * Robb Matzke <matzke@llnl.gov> * @@ -208,6 +208,61 @@ extern "C" { * above, this field contains the maximum number of bytes by which the * cache size can be increased in a single re-size. * + * flash_incr_mode: Instance of the H5C_cache_flash_incr_mode enumerated + * type whose value indicates whether and by which algorithm we should + * make flash increases in the size of the cache to accomodate insertion + * of large entries and large increases in the size of a single entry. + * + * The addition of the flash increment mode was occasioned by performance + * problems that appear when a local heap is increased to a size in excess + * of the current cache size. While the existing re-size code dealt with + * this eventually, performance was very bad for the remainder of the + * epoch. + * + * At present, there are two possible values for the flash_incr_mode: + * + * H5C_flash_incr__off: Don't perform flash increases in the size of + * the cache. + * + * H5C_flash_incr__add_space: Let x be either the size of a newly + * newly inserted entry, or the number of bytes by which the + * size of an existing entry has been increased. + * + * If + * x > flash_threshold * current max cache size, + * + * increase the current maximum cache size by x * flash_multiple + * less any free space in the cache, and star a new epoch. For + * now at least, pay no attention to the maximum increment. + * + * In both of the above cases, the flash increment pays no attention to + * the maximum increment (at least in this first incarnation), but DOES + * stay within max_size. + * + * With a little thought, it should be obvious that the above flash + * cache size increase algorithm is not sufficient for all circumstances -- + * for example, suppose the user round robins through + * (1/flash_threshold) +1 groups, adding one data set to each on each + * pass. Then all will increase in size at about the same time, requiring + * the max cache size to at least double to maintain acceptable + * performance, however the above flash increment algorithm will not be + * triggered. + * + * Hopefully, the add space algorithms detailed above will be sufficient + * for the performance problems encountered to date. However, we should + * expect to revisit the issue. + * + * flash_multiple: Double containing the multiple described above in the + * H5C_flash_incr__add_space section of the discussion of the + * flash_incr_mode section. This field is ignored unless flash_incr_mode + * is H5C_flash_incr__add_space. + * + * flash_threshold: Double containing the factor by which current max cache size + * is multiplied to obtain the size threshold for the add_space flash + * increment algorithm. The field is ignored unless flash_incr_mode is + * H5C_flash_incr__add_space. + * + * * * Cache size decrease control fields: * @@ -364,6 +419,10 @@ typedef struct H5AC_cache_config_t hbool_t apply_max_increment; size_t max_increment; + enum H5C_cache_flash_incr_mode flash_incr_mode; + double flash_multiple; + double flash_threshold; + /* size decrease control fields: */ enum H5C_cache_decr_mode decr_mode; |