/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Copyright by The HDF Group. * * 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://hdfgroup.org/HDF5/doc/Copyright.html. If you do not have * * access to either file, you may request a copy from help@hdfgroup.org. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ /* * Programmer: John Mainzer -- 4/19/06 * * Purpose: This file contains declarations which are normally visible * only within the H5AC package (just H5AC.c at present). * * Source files outside the H5AC package should include * H5ACprivate.h instead. * * The one exception to this rule is testpar/t_cache.c. The * test code is easier to write if it can look at H5AC_aux_t. * Indeed, this is the main reason why this file was created. * */ #ifndef H5AC_PACKAGE #error "Do not include this file outside the H5AC package!" #endif #ifndef _H5ACpkg_H #define _H5ACpkg_H /* Get package's private header */ #include "H5ACprivate.h" /* Metadata cache */ /* Get needed headers */ #include "H5Cprivate.h" /* Cache */ #include "H5SLprivate.h" /* Skip lists */ #define H5AC_DEBUG_DIRTY_BYTES_CREATION 0 /*------------------------------------------------------------------------- * It is a bit difficult to set ranges of allowable values on the * dirty_bytes_threshold field of H5AC_aux_t. The following are * probably broader than they should be. *------------------------------------------------------------------------- */ #define H5AC__MIN_DIRTY_BYTES_THRESHOLD (int32_t) \ (H5C__MIN_MAX_CACHE_SIZE / 2) #define H5AC__DEFAULT_DIRTY_BYTES_THRESHOLD (256 * 1024) #define H5AC__MAX_DIRTY_BYTES_THRESHOLD (int32_t) \ (H5C__MAX_MAX_CACHE_SIZE / 4) /**************************************************************************** * * structure H5AC_aux_t * * While H5AC has become a wrapper for the cache implemented in H5C.c, there * are some features of the metadata cache that are specific to it, and which * therefore do not belong in the more generic H5C cache code. * * In particular, there is the matter of synchronizing writes from the * metadata cache to disk in the PHDF5 case. * * Prior to this update, the presumption was that all metadata caches would * write the same data at the same time since all operations modifying * metadata must be performed collectively. Given this assumption, it was * safe to allow only the writes from process 0 to actually make it to disk, * while metadata writes from all other processes were discarded. * * Unfortunately, this presumption is in error as operations that read * metadata need not be collective, but can change the location of dirty * entries in the metadata cache LRU lists. This can result in the same * metadata write operation triggering writes from the metadata caches on * some processes, but not all (causing a hang), or in different sets of * entries being written from different caches (potentially resulting in * metadata corruption in the file). * * To deal with this issue, I decided to apply a paradigm shift to the way * metadata is written to disk. * * With this set of changes, only the metadata cache on process 0 is able * to write metadata to disk, although metadata caches on all other * processes can read metadata from disk as before. * * To keep all the other caches from getting plugged up with dirty metadata, * process 0 periodically broadcasts a list of entries that it has flushed * since that last notice, and which are currently clean. The other caches * mark these entries as clean as well, which allows them to evict the * entries as needed. * * One obvious problem in this approach is synchronizing the broadcasts * and receptions, as different caches may see different amounts of * activity. * * The current solution is for the caches to track the number of bytes * of newly generated dirty metadata, and to broadcast and receive * whenever this value exceeds some user specified threshold. * * Maintaining this count is easy for all processes not on process 0 -- * all that is necessary is to add the size of the entry to the total * whenever there is an insertion, a rename of a previously clean entry, * or whever a previously clean entry is marked dirty in an unprotect. * * On process 0, we have to be careful not to count dirty bytes twice. * If an entry is marked dirty, flushed, and marked dirty again, all * within a single reporting period, it only th first marking should * be added to the dirty bytes generated tally, as that is all that * the other processes will see. * * At present, this structure exists to maintain the fields needed to * implement the above scheme, and thus is only used in the parallel * case. However, other uses may arise in the future. * * Instance of this structure are associated with metadata caches via * the aux_ptr field of H5C_t (see H5Cpkg.h). The H5AC code is * responsible for allocating, maintaining, and discarding instances * of H5AC_aux_t. * * The remainder of this header comments documents the individual fields * of the structure. * * JRM - 6/27/05 * * magic: Unsigned 32 bit integer always set to * H5AC__H5AC_AUX_T_MAGIC. This field is used to validate * pointers to instances of H5AC_aux_t. * * mpi_comm: MPI communicator associated with the file for which the * cache has been created. * * mpi_rank: MPI rank of this process within mpi_comm. * * mpi_size: Number of processes in mpi_comm. * * write_permitted: Boolean flag used to control whether the cache * is permitted to write to file. * * dirty_bytes_threshold: Integer field containing the dirty bytes * generation threashold. Whenever dirty byte creation * exceeds this value, the metadata cache on process 0 * broadcasts a list of the entries it has flushed since * the last broadcast (or since the beginning of execution) * and which are currently clean (if they are still in the * cache) * * Similarly, metadata caches on processes other than process * 0 will attempt to receive a list of clean entries whenever * the threshold is exceeded. * * dirty_bytes: Integer field containing the number of bytes of dirty * metadata generated since the beginning of the computation, * or (more typically) since the last clean entries list * broadcast. This field is reset to zero after each such * broadcast. * * dirty_bytes_propagations: This field only exists when the * H5AC_DEBUG_DIRTY_BYTES_CREATION #define is TRUE. * * It is used to track the number of times the cleaned list * has been propagated from process 0 to the other * processes. * * unprotect_dirty_bytes: This field only exists when the * H5AC_DEBUG_DIRTY_BYTES_CREATION #define is TRUE. * * It is used to track the number of dirty bytes created * via unprotect operations since the last time the cleaned * list was propagated. * * unprotect_dirty_bytes_updates: This field only exists when the * H5AC_DEBUG_DIRTY_BYTES_CREATION #define is TRUE. * * It is used to track the number of times dirty bytes have * been created via unprotect operations since the last time * the cleaned list was propagated. * * insert_dirty_bytes: This field only exists when the * H5AC_DEBUG_DIRTY_BYTES_CREATION #define is TRUE. * * It is used to track the number of dirty bytes created * via insert operations since the last time the cleaned * list was propagated. * * insert_dirty_bytes_updates: This field only exists when the * H5AC_DEBUG_DIRTY_BYTES_CREATION #define is TRUE. * * It is used to track the number of times dirty bytes have * been created via insert operations since the last time * the cleaned list was propagated. * * rename_dirty_bytes: This field only exists when the * H5AC_DEBUG_DIRTY_BYTES_CREATION #define is TRUE. * * It is used to track the number of dirty bytes created * via rename operations since the last time the cleaned * list was propagated. * * rename_dirty_bytes_updates: This field only exists when the * H5AC_DEBUG_DIRTY_BYTES_CREATION #define is TRUE. * * It is used to track the number of times dirty bytes have * been created via rename operations since the last time * the cleaned list was propagated. * * d_slist_ptr: Pointer to an instance of H5SL_t used to maintain a list * of entries that have been dirtied since the last time they * were listed in a clean entries broadcast. This list is * only maintained by the metadata cache on process 0 -- it * it used to maintain a view of the dirty entries as seen * by the other caches, so as to keep the dirty bytes count * in synchronization with them. * * Thus on process 0, the dirty_bytes count is incremented * only if either * * 1) an entry is inserted in the metadata cache, or * * 2) a previously clean entry is renamed, and it does not * already appear in the dirty entry list, or * * 3) a previously clean entry is unprotected with the * dirtied flag set and the entry does not already appear * in the dirty entry list. * * Entries are added to the dirty entry list whever they cause * the dirty bytes count to be increased. They are removed * when they appear in a clean entries broadcast. Note that * renames must be reflected in the dirty entry list. * * To reitterate, this field is only used on process 0 -- it * should be NULL on all other processes. * * d_slist_len: Integer field containing the number of entries in the * dirty entry list. This field should always contain the * value 0 on all processes other than process 0. It exists * primarily for sanity checking. * * c_slist_ptr: Pointer to an instance of H5SL_t used to maintain a list * of entries that were dirty, have been flushed * to disk since the last clean entries broadcast, and are * still clean. Since only process 0 can write to disk, this * list only exists on process 0. * * In essence, this slist is used to assemble the contents of * the next clean entries broadcast. The list emptied after * each broadcast. * * c_slist_len: Integer field containing the number of entries in the clean * entries list (*c_slist_ptr). This field should always * contain the value 0 on all processes other than process 0. * It exists primarily for sanity checking. * * write_done: In the parallel test bed, it is necessary to ensure that * all writes to the server process from cache 0 complete * before it enters the barrier call with the other caches. * * The write_done callback allows t_cache to do this without * requiring an ACK on each write. Since these ACKs greatly * increase the run time on some platforms, this is a * significant optimization. * * This field must be set to NULL when the callback is not * needed. * ****************************************************************************/ #ifdef H5_HAVE_PARALLEL #define H5AC__H5AC_AUX_T_MAGIC (unsigned)0x00D0A02 typedef struct H5AC_aux_t { uint32_t magic; MPI_Comm mpi_comm; int mpi_rank; int mpi_size; hbool_t write_permitted; int32_t dirty_bytes_threshold; int32_t dirty_bytes; #if H5AC_DEBUG_DIRTY_BYTES_CREATION int32_t dirty_bytes_propagations; int32_t unprotect_dirty_bytes; int32_t unprotect_dirty_bytes_updates; int32_t insert_dirty_bytes; int32_t insert_dirty_bytes_updates; int32_t rename_dirty_bytes; int32_t rename_dirty_bytes_updates; #endif /* H5AC_DEBUG_DIRTY_BYTES_CREATION */ H5SL_t * d_slist_ptr; int32_t d_slist_len; H5SL_t * c_slist_ptr; int32_t c_slist_len; void (* write_done)(void); } H5AC_aux_t; /* struct H5AC_aux_t */ #endif /* H5_HAVE_PARALLEL */ #endif /* _H5ACpkg_H */