darshan-runtime commits for configurable mem

user can now give a config option or use a runtime environment
variable to control darshan's per module memory requirements.

darshan-log-format.h

@@ -69,6 +69,11 @@ static char * const darshan_module_names[] =
 };
 #undef X
 
+/* simple macros for accessing module flag bitfields */
+#define DARSHAN_MOD_FLAG_SET(flags, id) flags = (flags | (1 << id))
+#define DARSHAN_MOD_FLAG_UNSET(flags, id) flags = (flags & ~(1 << id))
+#define DARSHAN_MOD_FLAG_ISSET(flags, id) (flags & (1 << id))
+
 /* compression method used on darshan log file */
 enum darshan_comp_type
 {
@@ -97,7 +102,7 @@ struct darshan_header
     char version_string[8];
     int64_t magic_nr;
     unsigned char comp_type;
-    unsigned char partial_flag;
+    uint32_t partial_flag;
     struct darshan_log_map rec_map;
     struct darshan_log_map mod_map[DARSHAN_MAX_MODS];
 };

darshan-runtime/configure

@@ -693,7 +693,7 @@ with_log_hints
 with_log_path
 with_jobid_env
 enable_bgq_mod
-with_max_records
+with_mod_mem
 '
       ac_precious_vars='build_alias
 host_alias
@@ -1331,7 +1331,7 @@ Optional Packages:
   --with-jobid-env=<name> Name of environment variable that stores the jobid
     (specify "NONE" if no appropriate environment variable is available:
     Darshan will use rank 0's pid instead)
-  --with-max-records=<num>  Maximum records for Darshan to track at runtime
+  --with-mod-mem=<num>  Maximum amount of memory (in MiB) for each Darshan module
 
 Some influential environment variables:
   CC          C compiler command
@@ -4281,14 +4281,14 @@ rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 fi
 
 
-# Check whether --with-max-records was given.
-if test "${with_max_records+set}" = set; then :
-  withval=$with_max_records; if test x$withval = xyes; then
-        as_fn_error $? "--with-max-records must be given a number" "$LINENO" 5
+# Check whether --with-mod-mem was given.
+if test "${with_mod_mem+set}" = set; then :
+  withval=$with_mod_mem; if test x$withval = xyes; then
+        as_fn_error $? "--with-mod-mem must be given a number" "$LINENO" 5
     else
 
 cat >>confdefs.h <<_ACEOF
-#define __DARSHAN_MAX_RECORDS ${withval}
+#define __DARSHAN_MOD_MEM_MAX ${withval}
 _ACEOF
 
     fi

darshan-runtime/configure.in

@@ -300,12 +300,12 @@ if test x$enable_bgq_mod != xno; then
             []))
 fi
 
-AC_ARG_WITH(max-records,
-[  --with-max-records=<num>  Maximum records for Darshan to track at runtime],
+AC_ARG_WITH(mod-mem,
+[  --with-mod-mem=<num>  Maximum amount of memory (in MiB) for each Darshan module],
     if test x$withval = xyes; then
-        AC_MSG_ERROR(--with-max-records must be given a number)
+        AC_MSG_ERROR(--with-mod-mem must be given a number)
     else
-        AC_DEFINE_UNQUOTED(__DARSHAN_MAX_RECORDS, ${withval}, Maximum Darshan records to track at runtime)
+        AC_DEFINE_UNQUOTED(__DARSHAN_MOD_MEM_MAX, ${withval}, Maximum memory (in MiB) for each Darshan module)
     fi
 )
 

darshan-runtime/darshan-core.h

@@ -26,18 +26,18 @@
 /* Environment variable to override __DARSHAN_MEM_ALIGNMENT */
 #define DARSHAN_MEM_ALIGNMENT_OVERRIDE "DARSHAN_MEMALIGN"
 
-#ifdef __DARSHAN_MAX_RECORDS
-#define DARSHAN_CORE_MAX_RECORDS __DARSHAN_MAX_RECORDS
+/* Environment variable to override memory per module */
+#define DARSHAN_MOD_MEM_OVERRIDE "DARSHAN_MODMEM"
+
+/* Maximum amount of memory per instrumentation module in MiB */
+#ifdef __DARSHAN_MOD_MEM_MAX
+#define DARSHAN_MOD_MEM_MAX (__DARSHAN_MOD_MEM_MAX * 1024 * 1024)
 #else
-#define DARSHAN_CORE_MAX_RECORDS 2048
+#define DARSHAN_MOD_MEM_MAX (2 * 1024 * 1024) /* 2 MiB default */
 #endif
 
-/* TODO: revisit this default size if we change memory per module */
-#define DARSHAN_CORE_COMP_BUF_SIZE (2 * 1024 * 1024)
-
-#define DARSHAN_CORE_MOD_SET(flags, id) (flags | (1 << id))
-#define DARSHAN_CORE_MOD_UNSET(flags, id) (flags & ~(1 << id))
-#define DARSHAN_CORE_MOD_ISSET(flags, id) (flags & (1 << id))
+/* Default runtime compression buffer size */
+#define DARSHAN_COMP_BUF_SIZE DARSHAN_MOD_MEM_MAX
 
 /* in memory structure to keep up with job level data */
 struct darshan_core_runtime
@@ -48,7 +48,7 @@ struct darshan_core_runtime
     struct darshan_core_record_ref *rec_hash;
     int rec_count;
     struct darshan_core_module* mod_array[DARSHAN_MAX_MODS];
-    char comp_buf[DARSHAN_CORE_COMP_BUF_SIZE];
+    char comp_buf[DARSHAN_COMP_BUF_SIZE];
     double wtime_offset;
     char *trailing_data;
 };

darshan-runtime/darshan-runtime-config.h.in

@@ -102,11 +102,11 @@
 /* Location to store log files at run time */
 #undef __DARSHAN_LOG_PATH
 
-/* Maximum Darshan records to track at runtime */
-#undef __DARSHAN_MAX_RECORDS
-
 /* Memory alignment in bytes */
 #undef __DARSHAN_MEM_ALIGNMENT
 
+/* Maximum memory (in MiB) for each Darshan module */
+#undef __DARSHAN_MOD_MEM_MAX
+
 /* Generalized request type for MPI-IO */
 #undef __D_MPI_REQUEST

darshan-runtime/darshan.h

@@ -118,18 +118,21 @@ void darshan_core_unregister_module(
  * Register the Darshan record given by 'name' with the darshan-core
  * runtime, allowing it to be properly tracked and (potentially)
  * correlated with records from other modules. 'len' is the size of
- * the name pointer (string length for string names), 'printable_flag'
- * indicates whether the name is a string, and 'mod_id' is the identifier
- * of the calling module. 'rec_id' is an output pointer storing the
- * correspoing Darshan record identifier and 'file_alignment' is an
- * output pointer storing the file system alignment value for the given
- * record.
+ * the name pointer (string length for string names), and 'printable_flag'
+ * indicates whether the name is a string. 'mod_limit_flag' is set if
+ * the calling module is out of memory (to prevent darshan-core from
+ * creating new records and to just search existing records)  and 'mod_id'
+ * is the identifier of the calling module. 'rec_id' is an output pointer
+ * storing the correspoing Darshan record identifier and 'file_alignment'
+ * is an output pointer storing the file system alignment value for the
+ * given record.
  */
 void darshan_core_register_record(
     void *name,
     int len,
-    int printable_flag,
     darshan_module_id mod_id,
+    int printable_flag,
+    int mod_limit_flag,
     darshan_record_id *rec_id,
     int *file_alignment);
 

darshan-runtime/lib/darshan-bgq.c

@@ -156,8 +156,9 @@ void bgq_runtime_initialize()
     darshan_core_register_record(
         recname,
         strlen(recname),
-        1,
         DARSHAN_BGQ_MOD,
+        1,
+        0,
         &bgq_runtime->record.f_id,
         &bgq_runtime->record.alignment);
 

darshan-runtime/lib/darshan-core.c

@@ -99,7 +99,8 @@ static char* darshan_get_exe_and_mounts(
 static void darshan_block_size_from_path(
     const char *path, int *block_size);
 static void darshan_get_shared_records(
-    struct darshan_core_runtime *core, darshan_record_id *shared_recs);
+    struct darshan_core_runtime *core, darshan_record_id **shared_recs,
+    int *shared_rec_cnt);
 static int darshan_log_open_all(
     char *logfile_name, MPI_File *log_fh);
 static int darshan_deflate_buffer(
@@ -251,7 +252,9 @@ void darshan_core_shutdown()
     int64_t last_end_time;
     int local_mod_use[DARSHAN_MAX_MODS] = {0};
     int global_mod_use_count[DARSHAN_MAX_MODS] = {0};
-    darshan_record_id shared_recs[DARSHAN_CORE_MAX_RECORDS] = {0};
+    darshan_record_id *shared_recs;
+    darshan_record_id *mod_shared_recs;
+    int shared_rec_cnt = 0;
     double start_log_time;
     double open1, open2;
     double job1, job2;
@@ -261,7 +264,7 @@ void darshan_core_shutdown()
     double header1, header2;
     double tm_end;
     uint64_t gz_fp = 0;
-    unsigned char tmp_partial_flag;
+    uint32_t tmp_partial_flag;
     MPI_File log_fh;
     MPI_Status status;
 
@@ -368,7 +371,7 @@ void darshan_core_shutdown()
     DARSHAN_MPI_CALL(PMPI_Allreduce)(local_mod_use, global_mod_use_count, DARSHAN_MAX_MODS, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
 
     /* get a list of records which are shared across all processes */
-    darshan_get_shared_records(final_core, shared_recs);
+    darshan_get_shared_records(final_core, &shared_recs, &shared_rec_cnt);
 
     if(internal_timing_flag)
         open1 = DARSHAN_MPI_CALL(PMPI_Wtime)();
@@ -463,6 +466,9 @@ void darshan_core_shutdown()
     if(internal_timing_flag)
         rec2 = DARSHAN_MPI_CALL(PMPI_Wtime)();
 
+    mod_shared_recs = malloc(shared_rec_cnt * sizeof(darshan_record_id));
+    assert(mod_shared_recs);
+
     /* loop over globally used darshan modules and:
      *      - perform shared file reductions, if possible
      *      - get final output buffer
@@ -475,7 +481,6 @@ void darshan_core_shutdown()
     {
         struct darshan_core_module* this_mod = final_core->mod_array[i];
         struct darshan_core_record_ref *ref = NULL;
-        darshan_record_id mod_shared_recs[DARSHAN_CORE_MAX_RECORDS];
         int mod_shared_rec_cnt = 0;
         void* mod_buf = NULL;
         int mod_buf_sz = 0;
@@ -495,13 +500,13 @@ void darshan_core_shutdown()
             mod1[i] = DARSHAN_MPI_CALL(PMPI_Wtime)();
 
         /* set the shared file list for this module */
-        memset(mod_shared_recs, 0, DARSHAN_CORE_MAX_RECORDS * sizeof(darshan_record_id));
-        for(j = 0; j < DARSHAN_CORE_MAX_RECORDS && shared_recs[j] != 0; j++)
+        memset(mod_shared_recs, 0, shared_rec_cnt * sizeof(darshan_record_id));
+        for(j = 0; j < shared_rec_cnt; j++)
         {
             HASH_FIND(hlink, final_core->rec_hash, &shared_recs[j],
                 sizeof(darshan_record_id), ref);
             assert(ref);
-            if(DARSHAN_CORE_MOD_ISSET(ref->global_mod_flags, i))
+            if(DARSHAN_MOD_FLAG_ISSET(ref->global_mod_flags, i))
             {
                 mod_shared_recs[mod_shared_rec_cnt++] = shared_recs[j];
             }
@@ -551,11 +556,11 @@ void darshan_core_shutdown()
     }
 
     /* run a reduction to determine if any application processes had to set the
-     * partial flag. this happens when a process has tracked too many records
-     * at once and cannot track new records
+     * partial flag for any modules. this happens when a module exhausts its memory
+     * and does not track every possible record
      */
     DARSHAN_MPI_CALL(PMPI_Reduce)(&(final_core->log_header.partial_flag),
-        &tmp_partial_flag, 1, MPI_UNSIGNED_CHAR, MPI_MAX, 0, MPI_COMM_WORLD);
+        &tmp_partial_flag, 1, MPI_UINT32_T, MPI_BOR, 0, MPI_COMM_WORLD);
 
     if(internal_timing_flag)
         header1 = DARSHAN_MPI_CALL(PMPI_Wtime)();
@@ -1085,32 +1090,45 @@ static void darshan_block_size_from_path(const char *path, int *block_size)
 }
 
 static void darshan_get_shared_records(struct darshan_core_runtime *core,
-    darshan_record_id *shared_recs)
+    darshan_record_id **shared_recs, int *shared_rec_cnt)
 {
-    int i;
-    int ndx;
+    int i, j;
+    int tmp_cnt = core->rec_count;
     struct darshan_core_record_ref *tmp, *ref;
-    darshan_record_id id_array[DARSHAN_CORE_MAX_RECORDS] = {0};
-    uint64_t mod_flags[DARSHAN_CORE_MAX_RECORDS] = {0};
-    uint64_t global_mod_flags[DARSHAN_CORE_MAX_RECORDS] = {0};
+    darshan_record_id *id_array;
+    uint64_t *mod_flags;
+    uint64_t *global_mod_flags;
+
+    /* broadcast root's number of records to all other processes */
+    DARSHAN_MPI_CALL(PMPI_Bcast)(&tmp_cnt, 1, MPI_INT, 0, MPI_COMM_WORLD);
+
+    /* use root record count to allocate data structures */
+    id_array = malloc(tmp_cnt * sizeof(darshan_record_id));
+    mod_flags = malloc(tmp_cnt * sizeof(uint64_t));
+    global_mod_flags = malloc(tmp_cnt * sizeof(uint64_t));
+    *shared_recs = malloc(tmp_cnt * sizeof(darshan_record_id));
+    assert(id_array && mod_flags && global_mod_flags && *shared_recs);
+
+    memset(mod_flags, 0, tmp_cnt * sizeof(uint64_t));
+    memset(global_mod_flags, 0, tmp_cnt * sizeof(uint64_t));
+    memset(*shared_recs, 0, tmp_cnt * sizeof(darshan_record_id));
 
     /* first, determine list of records root process has opened */
     if(my_rank == 0)
     {
-        ndx = 0;
+        i = 0;
         HASH_ITER(hlink, core->rec_hash, ref, tmp)
         {
-            id_array[ndx++] = ref->rec.id;           
+            id_array[i++] = ref->rec.id;           
         }
     }
 
     /* broadcast root's list of records to all other processes */
-    DARSHAN_MPI_CALL(PMPI_Bcast)(id_array,
-        (DARSHAN_CORE_MAX_RECORDS * sizeof(darshan_record_id)),
+    DARSHAN_MPI_CALL(PMPI_Bcast)(id_array, (tmp_cnt * sizeof(darshan_record_id)),
         MPI_BYTE, 0, MPI_COMM_WORLD);
 
     /* everyone looks to see if they opened the same records as root */
-    for(i=0; (i<DARSHAN_CORE_MAX_RECORDS && id_array[i] != 0); i++)
+    for(i=0; i<tmp_cnt; i++)
     {
         HASH_FIND(hlink, core->rec_hash, &id_array[i], sizeof(darshan_record_id), ref);
         if(ref)
@@ -1123,15 +1141,15 @@ static void darshan_get_shared_records(struct darshan_core_runtime *core,
     /* now allreduce so everyone agrees which files are shared and
      * which modules accessed them collectively
      */
-    DARSHAN_MPI_CALL(PMPI_Allreduce)(mod_flags, global_mod_flags,
-        DARSHAN_CORE_MAX_RECORDS, MPI_UINT64_T, MPI_BAND, MPI_COMM_WORLD);
+    DARSHAN_MPI_CALL(PMPI_Allreduce)(mod_flags, global_mod_flags, tmp_cnt,
+        MPI_UINT64_T, MPI_BAND, MPI_COMM_WORLD);
 
-    ndx = 0;
-    for(i=0; (i<DARSHAN_CORE_MAX_RECORDS && id_array[i] != 0); i++)
+    j = 0;
+    for(i=0; i<tmp_cnt; i++)
     {
         if(global_mod_flags[i] != 0)
         {
-            shared_recs[ndx++] = id_array[i];
+            (*shared_recs)[j++] = id_array[i];
 
             /* set global_mod_flags so we know which modules collectively
              * accessed this module. we need this info to support shared
@@ -1142,6 +1160,7 @@ static void darshan_get_shared_records(struct darshan_core_runtime *core,
             ref->global_mod_flags = global_mod_flags[i];
         }
     }
+    *shared_rec_cnt = j;
 
     return;
 }
@@ -1246,7 +1265,7 @@ static int darshan_deflate_buffer(void **pointers, int *lengths, int count,
     }
 
     tmp_stream.next_out = (unsigned char *)comp_buf;
-    tmp_stream.avail_out = DARSHAN_CORE_COMP_BUF_SIZE;
+    tmp_stream.avail_out = DARSHAN_COMP_BUF_SIZE;
 
     /* loop over the input pointers */
     for(i = 0; i < count; i++)
@@ -1307,9 +1326,9 @@ static int darshan_log_write_record_hash(MPI_File log_fh, struct darshan_core_ru
     char *hash_buf;
     char *hash_buf_off;
 
-    /* allocate a buffer to store at most 64 bytes for each of a max number of records */
+    /* allocate a buffer to store at most 64 bytes for each registered record */
     /* NOTE: this buffer may be reallocated if estimate is too small */
-    hash_buf_sz = DARSHAN_CORE_MAX_RECORDS * 64;
+    hash_buf_sz = core->rec_count * 64;
     hash_buf = malloc(hash_buf_sz);
     if(!hash_buf)
     {
@@ -1478,7 +1497,10 @@ void darshan_core_register_module(
     int *mod_mem_limit,
     int *sys_mem_alignment)
 {
+    int ret;
+    int tmpval;
     struct darshan_core_module* mod;
+    char *mod_mem_str = NULL;
     *mod_mem_limit = 0;
 
     if(!darshan_core || (mod_id >= DARSHAN_MAX_MODS))
@@ -1514,9 +1536,21 @@ void darshan_core_register_module(
     /* get the calling process's rank */
     DARSHAN_MPI_CALL(PMPI_Comm_rank)(MPI_COMM_WORLD, my_rank);
 
-    /* TODO: something smarter than just 2 MiB per module */
-    *mod_mem_limit = 2 * 1024 * 1024;
-
+    /* set the maximum amount of memory this module can use */
+    mod_mem_str = getenv(DARSHAN_MOD_MEM_OVERRIDE);
+    if(mod_mem_str)
+    {
+        ret = sscanf(mod_mem_str, "%d", &tmpval);
+        /* silently ignore if the env variable is set poorly */
+        if(ret == 1 && tmpval > 0)
+            *mod_mem_limit = (tmpval * 1024 * 1024); /* convert to MiB */
+        else
+            *mod_mem_limit = DARSHAN_MOD_MEM_MAX;
+    }
+    else
+    {
+        *mod_mem_limit = DARSHAN_MOD_MEM_MAX;
+    }
     DARSHAN_CORE_UNLOCK();
 
     return;
@@ -1550,8 +1584,9 @@ void darshan_core_unregister_module(
 void darshan_core_register_record(
     void *name,
     int len,
-    int printable_flag,
     darshan_module_id mod_id,
+    int printable_flag,
+    int mod_limit_flag,
     darshan_record_id *rec_id,
     int *file_alignment)
 {
@@ -1573,16 +1608,14 @@ void darshan_core_register_record(
     HASH_FIND(hlink, darshan_core->rec_hash, &tmp_rec_id, sizeof(darshan_record_id), ref);
     if(!ref)
     {
-        /* record not found -- add it to the hash if we aren't already tracking the
-         * maximum number of records
+        /* record not found -- add it to the hash if this module has not already used
+         * all of its memory
          */
   
-        if(darshan_core->rec_count >= DARSHAN_CORE_MAX_RECORDS)
+        if(mod_limit_flag)
         {
-            /* if we are already tracking the max records, set a flag to indicate
-             * that this log file has partial results
-             */
-            darshan_core->log_header.partial_flag = 1;
+            /* if this module is OOM, set a flag in the header to indicate this */
+            DARSHAN_MOD_FLAG_SET(darshan_core->log_header.partial_flag, mod_id);
             DARSHAN_CORE_UNLOCK();
             return;
         }
@@ -1600,7 +1633,7 @@ void darshan_core_register_record(
             darshan_core->rec_count++;
         }
     }
-    ref->mod_flags = DARSHAN_CORE_MOD_SET(ref->mod_flags, mod_id);
+    DARSHAN_MOD_FLAG_SET(ref->mod_flags, mod_id);
     DARSHAN_CORE_UNLOCK();
 
     if(file_alignment)
@@ -1625,7 +1658,7 @@ void darshan_core_unregister_record(
     assert(ref); 
 
     /* disassociate this module from the given record id */
-    ref->mod_flags = DARSHAN_CORE_MOD_UNSET(ref->mod_flags, mod_id);
+    DARSHAN_MOD_FLAG_UNSET(ref->mod_flags, mod_id);
     if(!(ref->mod_flags))
     {
         /* if no other modules are associated with this rec, delete it */

darshan-runtime/lib/darshan-hdf5.c

@@ -256,6 +256,7 @@ static struct hdf5_file_runtime* hdf5_file_by_name(const char *name)
     struct hdf5_file_runtime *file = NULL;
     char *newname = NULL;
     darshan_record_id file_id;
+    int limit_flag;
 
     if(!hdf5_runtime || instrumentation_disabled)
         return(NULL);
@@ -264,12 +265,15 @@ static struct hdf5_file_runtime* hdf5_file_by_name(const char *name)
     if(!newname)
         newname = (char*)name;
 
+    limit_flag = (hdf5_runtime->file_array_ndx >= hdf5_runtime->file_array_size);
+
     /* get a unique id for this file from darshan core */
     darshan_core_register_record(
         (void*)newname,
         strlen(newname),
-        1,
         DARSHAN_HDF5_MOD,
+        1,
+        limit_flag,
         &file_id,
         NULL);
 
@@ -292,19 +296,15 @@ static struct hdf5_file_runtime* hdf5_file_by_name(const char *name)
         return(file);
     }
 
-    if(hdf5_runtime->file_array_ndx < hdf5_runtime->file_array_size);
-    {
-        /* no existing record, assign a new file record from the global array */
-        file = &(hdf5_runtime->file_runtime_array[hdf5_runtime->file_array_ndx]);
-        file->file_record = &(hdf5_runtime->file_record_array[hdf5_runtime->file_array_ndx]);
-        file->file_record->f_id = file_id;
-        file->file_record->rank = my_rank;
-
-        /* add new record to file hash table */
-        HASH_ADD(hlink, hdf5_runtime->file_hash, file_record->f_id, sizeof(darshan_record_id), file);
+    /* no existing record, assign a new file record from the global array */
+    file = &(hdf5_runtime->file_runtime_array[hdf5_runtime->file_array_ndx]);
+    file->file_record = &(hdf5_runtime->file_record_array[hdf5_runtime->file_array_ndx]);
+    file->file_record->f_id = file_id;
+    file->file_record->rank = my_rank;
 
-        hdf5_runtime->file_array_ndx++;
-    }
+    /* add new record to file hash table */
+    HASH_ADD(hlink, hdf5_runtime->file_hash, file_record->f_id, sizeof(darshan_record_id), file);
+    hdf5_runtime->file_array_ndx++;
 
     if(newname != name)
         free(newname);

darshan-runtime/lib/darshan-mpiio.c

@@ -878,6 +878,7 @@ static struct mpiio_file_runtime* mpiio_file_by_name(const char *name)
     struct mpiio_file_runtime *file = NULL;
     char *newname = NULL;
     darshan_record_id file_id;
+    int limit_flag;
 
     if(!mpiio_runtime || instrumentation_disabled)
         return(NULL);
@@ -886,17 +887,20 @@ static struct mpiio_file_runtime* mpiio_file_by_name(const char *name)
     if(!newname)
         newname = (char*)name;
 
+    limit_flag = (mpiio_runtime->file_array_ndx >= mpiio_runtime->file_array_size);
+
     /* get a unique id for this file from darshan core */
     darshan_core_register_record(
         (void*)newname,
         strlen(newname),
-        1,
         DARSHAN_MPIIO_MOD,
+        1,
+        limit_flag,
         &file_id,
         NULL);
 
-    /* if record is set to 0, darshan-core is out of space and will not
-     * track this record, so we should avoid tracking it, too
+    /* the file record id is set to 0 if no memory is available for tracking
+     * new records -- just fall through and ignore this record
      */
     if(file_id == 0)
     {
@@ -914,19 +918,15 @@ static struct mpiio_file_runtime* mpiio_file_by_name(const char *name)
         return(file);
     }
 
-    if(mpiio_runtime->file_array_ndx < mpiio_runtime->file_array_size);
-    {
-        /* no existing record, assign a new file record from the global array */
-        file = &(mpiio_runtime->file_runtime_array[mpiio_runtime->file_array_ndx]);
-        file->file_record = &(mpiio_runtime->file_record_array[mpiio_runtime->file_array_ndx]);
-        file->file_record->f_id = file_id;
-        file->file_record->rank = my_rank;
-
-        /* add new record to file hash table */
-        HASH_ADD(hlink, mpiio_runtime->file_hash, file_record->f_id, sizeof(darshan_record_id), file);
+    /* no existing record, assign a new file record from the global array */
+    file = &(mpiio_runtime->file_runtime_array[mpiio_runtime->file_array_ndx]);
+    file->file_record = &(mpiio_runtime->file_record_array[mpiio_runtime->file_array_ndx]);
+    file->file_record->f_id = file_id;
+    file->file_record->rank = my_rank;
 
-        mpiio_runtime->file_array_ndx++;
-    }
+    /* add new record to file hash table */
+    HASH_ADD(hlink, mpiio_runtime->file_hash, file_record->f_id, sizeof(darshan_record_id), file);
+    mpiio_runtime->file_array_ndx++;
 
     if(newname != name)
         free(newname);

darshan-runtime/lib/darshan-null.c

@@ -264,6 +264,7 @@ static struct null_record_runtime* null_record_by_name(const char *name)
 {
     struct null_record_runtime *rec = NULL;
     darshan_record_id rec_id;
+    int limit_flag;
 
     /* Don't search for a record if the "NULL" module is not initialized or
      * if instrumentation has been toggled off.
@@ -271,15 +272,27 @@ static struct null_record_runtime* null_record_by_name(const char *name)
     if(!null_runtime || instrumentation_disabled)
         return(NULL);
 
+    /* stop tracking new records if we are tracking our maximum count */
+    limit_flag = (null_runtime->rec_array_ndx >= null_runtime->rec_array_size);
+
     /* get a unique record identifier for this record from darshan-core */
     darshan_core_register_record(
         (void*)name,
         strlen(name),
-        1,
         DARSHAN_NULL_MOD,
+        1,
+        limit_flag,
         &rec_id,
         NULL);
 
+    /* the file record id is set to 0 if no memory is available for tracking
+     * new records -- just fall through and ignore this record
+     */
+    if(rec_id == 0)
+    {
+        return(NULL);
+    }
+
     /* search the hash table for this file record, and return if found */
     HASH_FIND(hlink, null_runtime->record_hash, &rec_id, sizeof(darshan_record_id), rec);
     if(rec)
@@ -287,21 +300,17 @@ static struct null_record_runtime* null_record_by_name(const char *name)
         return(rec);
     }
 
-    if(null_runtime->rec_array_ndx < null_runtime->rec_array_size);
-    {
-        /* no existing record, assign a new one from the global array */
-        rec = &(null_runtime->runtime_record_array[null_runtime->rec_array_ndx]);
-        rec->record_p = &(null_runtime->record_array[null_runtime->rec_array_ndx]);
+    /* no existing record, assign a new one from the global array */
+    rec = &(null_runtime->runtime_record_array[null_runtime->rec_array_ndx]);
+    rec->record_p = &(null_runtime->record_array[null_runtime->rec_array_ndx]);
 
-        /* set the darshan record id and corresponding process rank for this record */
-        rec->record_p->f_id = rec_id;
-        rec->record_p->rank = my_rank;
+    /* set the darshan record id and corresponding process rank for this record */
+    rec->record_p->f_id = rec_id;
+    rec->record_p->rank = my_rank;