[svn-r10688] Purpose:

Add API calls allowing user control of the metadata cache.


Description:

Prior to this update, the metadata cache was not configurable
from outside the library.


Solution:

Add API calls allowing the user to configure the metadata cache
either at file open time, or for any open file.  Also added calls
permitting the user to monitor cache size and hit rate.  These
latter facilities are needed for "manual" cache size control


Platforms tested:

h5committested


Misc. update:

1 files changed, 243 insertions, 0 deletions

diff --git a/src/H5ACpublic.h b/src/H5ACpublic.h
index 9eb5156..fab825b 100644
--- a/src/H5ACpublic.h
+++ b/src/H5ACpublic.h
@@ -29,11 +29,254 @@
 
 /* Public headers needed by this file */
 #include "H5public.h"
+#include "H5Cpublic.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+/****************************************************************************
+ *
+ * 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.
+ *
+ * The structure is in H5ACpublic.h as we may wish to allow different
+ * configuration options for metadata and raw data caches.
+ *
+ * The fields of the structure are discussed individually below:
+ *
+ * version: Integer field containing the version number of this version
+ *      of the H5AC_cache_config_t structure.  Any instance of
+ *      H5AC_cache_config_t passed to the cache must have a known
+ *      version number, or an error will be flagged.
+ *
+ * rpt_fcn_enabled: Boolean field used to enable and disable the default
+ *	reporting function.  This function is invoked every time the 
+ *	automatic cache resize code is run, and reports on its activities.
+ *
+ *	This is a debugging function, and should normally be turned off.
+ *
+ * set_initial_size: Boolean flag indicating whether the size of the
+ *      initial size of the cache is to be set to the value given in
+ *      the initial_size field.  If set_initial_size is FALSE, the
+ *      initial_size field is ignored.
+ *
+ * initial_size: If enabled, this field contain the size the cache is
+ *      to be set to upon receipt of this structure.  Needless to say,
+ *      initial_size must lie in the closed interval [min_size, max_size].
+ *
+ * min_clean_fraction: double in the range 0 to 1 indicating the fraction
+ *      of the cache that is to be kept clean.  This field is only used
+ *      in parallel mode.  Typical values are 0.1 to 0.5.
+ *
+ * max_size: Maximum size to which the cache can be adjusted.  The
+ *      supplied value must fall in the closed interval
+ *      [MIN_MAX_CACHE_SIZE, MAX_MAX_CACHE_SIZE].  Also, max_size must
+ *      be greater than or equal to min_size.
+ *
+ * min_size: Minimum size to which the cache can be adjusted.  The
+ *      supplied value must fall in the closed interval
+ *      [H5C__MIN_MAX_CACHE_SIZE, H5C__MAX_MAX_CACHE_SIZE].  Also, min_size
+ *      must be less than or equal to max_size.
+ *
+ * epoch_length: Number of accesses on the cache over which to collect
+ *      hit rate stats before running the automatic cache resize code,
+ *      if it is enabled.
+ *
+ *      At the end of an epoch, we discard prior hit rate data and start
+ *      collecting afresh.  The epoch_length must lie in the closed
+ *      interval [H5C__MIN_AR_EPOCH_LENGTH, H5C__MAX_AR_EPOCH_LENGTH].
+ *
+ *
+ * Cache size increase control fields:
+ *
+ * incr_mode: Instance of the H5C_cache_incr_mode enumerated type whose
+ *      value indicates how we determine whether the cache size should be
+ *      increased.  At present there are two possible values:
+ *
+ *      H5C_incr__off:  Don't attempt to increase the size of the cache
+ *              automatically.
+ *
+ *              When this increment mode is selected, the remaining fields
+ *              in the cache size increase section ar ignored.
+ *
+ *      H5C_incr__threshold: Attempt to increase the size of the cache
+ *              whenever the average hit rate over the last epoch drops
+ *              below the value supplied in the lower_hr_threshold
+ *              field.
+ *
+ *              Note that this attempt will fail if the cache is already
+ *              at its maximum size, or if the cache is not already using
+ *              all available space.
+ *
+ * lower_hr_threshold: Lower hit rate threshold.  If the increment mode
+ *      (incr_mode) is H5C_incr__threshold and the hit rate drops below the
+ *      value supplied in this field in an epoch, increment the cache size by
+ *      size_increment.  Note that cache size may not be incremented above
+ *      max_size, and that the increment may be further restricted by the
+ *      max_increment field if it is enabled.
+ *
+ *      When enabled, this field must contain a value in the range [0.0, 1.0].
+ *      Depending on the incr_mode selected, it may also have to be less than
+ *      upper_hr_threshold.
+ *
+ * increment:  Double containing the multiplier used to derive the new
+ *      cache size from the old if a cache size increment is triggered.
+ *      The increment must be greater than 1.0, and should not exceed 2.0.
+ *
+ *      The new cache size is obtained my multiplying the current max cache
+ *      size by the increment, and then clamping to max_size and to stay
+ *      within the max_increment as necessary.
+ *
+ * apply_max_increment:  Boolean flag indicating whether the max_increment
+ *      field should be used to limit the maximum cache size increment.
+ *
+ * max_increment: If enabled by the apply_max_increment field described
+ *      above, this field contains the maximum number of bytes by which the
+ *      cache size can be increased in a single re-size.
+ *
+ *
+ * Cache size decrease control fields:
+ *
+ * decr_mode: Instance of the H5C_cache_decr_mode enumerated type whose
+ *      value indicates how we determine whether the cache size should be
+ *      decreased.  At present there are four possibilities.
+ *
+ *      H5C_decr__off:  Don't attempt to decrease the size of the cache
+ *              automatically.
+ *
+ *              When this increment mode is selected, the remaining fields
+ *              in the cache size decrease section are ignored.
+ *
+ *      H5C_decr__threshold: Attempt to decrease the size of the cache
+ *              whenever the average hit rate over the last epoch rises
+ *              above the value supplied in the upper_hr_threshold
+ *              field.
+ *
+ *      H5C_decr__age_out:  At the end of each epoch, search the cache for
+ *              entries that have not been accessed for at least the number
+ *              of epochs specified in the epochs_before_eviction field, and
+ *              evict these entries.  Conceptually, the maximum cache size
+ *              is then decreased to match the new actual cache size.  However,
+ *              this reduction may be modified by the min_size, the
+ *              max_decrement, and/or the empty_reserve.
+ *
+ *      H5C_decr__age_out_with_threshold:  Same as age_out, but we only
+ *              attempt to reduce the cache size when the hit rate observed
+ *              over the last epoch exceeds the value provided in the
+ *              upper_hr_threshold field.
+ *
+ * upper_hr_threshold: Upper hit rate threshold.  The use of this field
+ *      varies according to the current decr_mode:
+ *
+ *      H5C_decr__off or H5C_decr__age_out:  The value of this field is
+ *              ignored.
+ *
+ *      H5C_decr__threshold:  If the hit rate exceeds this threshold in any
+ *              epoch, attempt to decrement the cache size by size_decrement.
+ *
+ *              Note that cache size may not be decremented below min_size.
+ *
+ *              Note also that if the upper_threshold is 1.0, the cache size
+ *              will never be reduced.
+ *
+ *      H5C_decr__age_out_with_threshold:  If the hit rate exceeds this
+ *              threshold in any epoch, attempt to reduce the cache size
+ *              by evicting entries that have not been accessed for more
+ *              than the specified number of epochs.
+ *
+ * decrement: This field is only used when the decr_mode is
+ *      H5C_decr__threshold.
+ *
+ *      The field is a double containing the multiplier used to derive the
+ *      new cache size from the old if a cache size decrement is triggered.
+ *      The decrement must be in the range 0.0 (in which case the cache will
+ *      try to contract to its minimum size) to 1.0 (in which case the
+ *      cache will never shrink).
+ *
+ * apply_max_decrement:  Boolean flag used to determine whether decrements
+ *      in cache size are to be limited by the max_decrement field.
+ *
+ * max_decrement: Maximum number of bytes by which the cache size can be
+ *      decreased in a single re-size.  Note that decrements may also be
+ *      restricted by the min_size of the cache, and (in age out modes) by
+ *      the empty_reserve field.
+ *
+ * epochs_before_eviction:  Integer field used in H5C_decr__age_out and
+ *      H5C_decr__age_out_with_threshold decrement modes.
+ *
+ *      This field contains the number of epochs an entry must remain
+ *      unaccessed before it is evicted in an attempt to reduce the
+ *      cache size.  If applicable, this field must lie in the range
+ *      [1, H5C__MAX_EPOCH_MARKERS].
+ *
+ * apply_empty_reserve:  Boolean field controlling whether the empty_reserve
+ *      field is to be used in computing the new cache size when the
+ *      decr_mode is H5C_decr__age_out or H5C_decr__age_out_with_threshold.
+ *
+ * empty_reserve:  To avoid a constant racheting down of cache size by small
+ *      amounts in the H5C_decr__age_out and H5C_decr__age_out_with_threshold
+ *      modes, this field allows one to require that any cache size
+ *      reductions leave the specified fraction of unused space in the cache.
+ *
+ *      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.
+ *
+ ****************************************************************************/
+
+#define H5AC__CURR_CACHE_CONFIG_VERSION  1
+
+typedef struct H5AC_cache_config_t
+{
+    /* general configuration fields: */
+    int32_t                     version;
+
+    hbool_t			rpt_fcn_enabled;
+
+    hbool_t                     set_initial_size;
+    size_t                      initial_size;
+
+    double                      min_clean_fraction;
+
+    size_t                      max_size;
+    size_t                      min_size;
+
+    int64_t                     epoch_length;
+
+
+    /* size increase control fields: */
+    enum H5C_cache_incr_mode    incr_mode;
+
+    double                      lower_hr_threshold;
+
+    double                      increment;
+
+    hbool_t                     apply_max_increment;
+    size_t                      max_increment;
+
+
+    /* size decrease control fields: */
+    enum H5C_cache_decr_mode    decr_mode;
+
+    double                      upper_hr_threshold;
+
+    double                      decrement;
+
+    hbool_t                     apply_max_decrement;
+    size_t                      max_decrement;
+
+    int32_t                     epochs_before_eviction;
+
+    hbool_t                     apply_empty_reserve;
+    double                      empty_reserve;
+
+} H5AC_cache_config_t;
+
+
 #ifdef __cplusplus
 }
 #endif