promote server counters to 64 bits

the struct alignment is important here, as we are going to read this
struct once to get the fixed values and a second time to fill in the
extra histogram buckets.

darshan-mdhim-log-format.h

@@ -63,9 +63,12 @@ struct darshan_mdhim_record
     double fcounters[MDHIM_F_NUM_INDICES];
     /* when we allocate this struct, we'll do so with enough extra memory to
      * hold N servers.  Compare to approach taken with darshan_lustre_record */
-    int32_t server_histogram[1];
+    /* be mindful of struct alignment here:  If one reads "sizeof(struct
+     * darshan_mdhim_record)", one might end up reading more than expected.
+     * Second read will then end up reading less than needed */
+    int64_t server_histogram[1];
 };
 
 /* '-1' because d_m_r already allocated with space for one */
-#define MDHIM_RECORD_SIZE(servers) (sizeof(struct darshan_mdhim_record) + sizeof(int32_t) * ((servers) - 1) )
+#define MDHIM_RECORD_SIZE(servers) (sizeof(struct darshan_mdhim_record) + sizeof(int64_t) * ((servers) - 1) )
 #endif /* __DARSHAN_MDHIM_LOG_FORMAT_H */

darshan-util/darshan-mdhim-logutils.c

@@ -89,7 +89,7 @@ static int darshan_log_get_mdhim_record(darshan_fd fd, void** mdhim_buf_p)
             DARSHAN_BSWAP64(&tmp_rec.counters[i]);
         for (i=0; i< MDHIM_F_NUM_INDICES; i++)
             DARSHAN_BSWAP64(&tmp_rec.fcounters[i]);
-        DARSHAN_BSWAP32(&(tmp_rec.server_histogram[0]) );
+        DARSHAN_BSWAP64(&(tmp_rec.server_histogram[0]) );
     }
 
     if(*mdhim_buf_p == NULL)
@@ -103,16 +103,16 @@ static int darshan_log_get_mdhim_record(darshan_fd fd, void** mdhim_buf_p)
     if (rec->counters[MDHIM_SERVERS] > 1) {
         ret = darshan_log_get_mod(fd, DARSHAN_MDHIM_MOD,
                 &(rec->server_histogram[1]),
-                (rec->counters[MDHIM_SERVERS] - 1)*sizeof(int32_t));
+                (rec->counters[MDHIM_SERVERS] - 1)*sizeof(int64_t));
 
-        if (ret < (rec->counters[MDHIM_SERVERS] -1)*sizeof(int32_t))
+        if (ret < (rec->counters[MDHIM_SERVERS] -1)*sizeof(int64_t))
             ret = -1;
         else
         {
             ret = 1;
             if (fd->swap_flag)
                 for(i=1; i< rec->counters[MDHIM_SERVERS]; i++)
-                    DARSHAN_BSWAP32(&(rec->server_histogram[i]));
+                    DARSHAN_BSWAP64(&(rec->server_histogram[i]));
         }
     }
     else