diff options
Diffstat (limited to 'src/H5ACpublic.h')
| -rw-r--r-- | src/H5ACpublic.h | 47 |
1 files changed, 44 insertions, 3 deletions
diff --git a/src/H5ACpublic.h b/src/H5ACpublic.h index 2381ccc..5db8c5a 100644 --- a/src/H5ACpublic.h +++ b/src/H5ACpublic.h @@ -40,9 +40,18 @@ extern "C" { * structure H5AC_cache_config_t * * H5AC_cache_config_t is a public structure intended for use in public APIs. - * At least in its initial incarnation, it is a essentially a copy of - * struct H5C_auto_size_ctl_t, minus the report_fcn field. This is omitted, - * as including it would require us to make H5C_t structure public. + * At least in its initial incarnation, it is basicaly a copy of struct + * H5C_auto_size_ctl_t, minus the report_fcn field, and plus the + * dirty_bytes_threshold field. + * + * The report_fcn field is omitted, as including it would require us to + * make H5C_t structure public. + * + * The dirty_bytes_threshold field does not appear in H5C_auto_size_ctl_t, + * as synchronization between caches on different processes is handled at + * the H5AC level, not at the level of H5C. Note however that there is + * considerable interaction between this value and the other fields in this + * structure. * * The structure is in H5ACpublic.h as we may wish to allow different * configuration options for metadata and raw data caches. @@ -226,6 +235,34 @@ extern "C" { * The value of this field must be in the range [0.0, 1.0]. I would * expect typical values to be in the range of 0.01 to 0.1. * + * + * Parallel Configuration Fields: + * + * In PHDF5, all operations that modify metadata must be executed collectively. + * We used to think that this was enough to ensure consistency across the + * metadata caches, but since we allow processes to read metadata individually, + * the order of dirty entries in the LRU list can vary across processes, + * which can result in inconsistencies between the caches. + * + * To prevent this, only the metadata cache on process 0 is allowed to write + * to file, and then only after synchronizing with the other caches. After + * it writes entries to file, it sends the base addresses of the now clean + * entries to the other caches, so they can mark these entries clean as well. + * + * The different caches know when to synchronize caches by counting the + * number of bytes of dirty metadata created by the collective operations + * modifying metadata. Whenever this count exceeds a user specified + * threshold (see below), process 0 flushes down to its minimum clean size, + * and then sends the list of newly cleaned entries to the other caches. + * + * dirty_bytes_threshold: Threshold of dirty byte creation used to + * synchronize updates between caches. (See above for outline and + * motivation.) + * + * This value MUST be consistant across all processes accessing the + * file. This field is ignored unless HDF5 has been compiled for + * parallel. + * ****************************************************************************/ #define H5AC__CURR_CACHE_CONFIG_VERSION 1 @@ -274,6 +311,10 @@ typedef struct H5AC_cache_config_t hbool_t apply_empty_reserve; double empty_reserve; + + /* parallel configuration fields: */ + int dirty_bytes_threshold; + } H5AC_cache_config_t; |