[svn-r24993] Purpose:

Adds write tracking to the core VFD, which can be configured
via the H5Pset/get_core_write_tracking() API call. When enabled
and writing to the backing store is enabled, this feature will
track writes and only write out the changed bytes on flush/close.

Tested on:
    32-bit LE linux (jam) w/ Fortran and C++
    64-bit BE linux (ostrich)
    64-bit Darwin 12.5.0 (kite)

All were tested using the core VFD w/ paging on (core_paged
in the VFD list). Make check-vfd was also tested on jam.

14 files changed, 529 insertions, 91 deletions

diff --git a/src/H5FDcore.c b/src/H5FDcore.c
index 74aeed3..2f51264 100644
--- a/src/H5FDcore.c
+++ b/src/H5FDcore.c
@@ -25,19 +25,26 @@
 /* Interface initialization */
 #define H5_INTERFACE_INIT_FUNC	H5FD_core_init_interface
 
-
 #include "H5private.h"      /* Generic Functions            */
 #include "H5Eprivate.h"     /* Error handling               */
 #include "H5Fprivate.h"     /* File access                  */
 #include "H5FDprivate.h"    /* File drivers                 */
 #include "H5FDcore.h"       /* Core file driver             */
+#include "H5FLprivate.h"    /* Free lists                   */
 #include "H5Iprivate.h"     /* IDs                          */
 #include "H5MMprivate.h"    /* Memory management            */
 #include "H5Pprivate.h"     /* Property lists               */
+#include "H5SLprivate.h"    /* Skip lists                   */
 
 /* The driver identification number, initialized at runtime */
 static hid_t H5FD_CORE_g = 0;
 
+/* The skip list node type.  Represents a region in the file. */
+typedef struct H5FD_core_region_t {
+    haddr_t start;              /* Start address of the region          */
+    haddr_t end;                /* End address of the region            */
+} H5FD_core_region_t;
+
 /* The description of a file belonging to this driver. The 'eoa' and 'eof'
  * determine the amount of hdf5 address space in use and the high-water mark
  * of the file (the current size of the underlying memory).
@@ -50,6 +57,7 @@ typedef struct H5FD_core_t {
     haddr_t eof;                /* current allocated size               */
     size_t  increment;          /* multiples for mem allocation         */
     hbool_t backing_store;      /* write to file name on flush          */
+    size_t  bstore_page_size;   /* backing store page size              */
     int     fd;                 /* backing store file descriptor        */
     /* Information for determining uniqueness of a file with a backing store */
 #ifndef H5_HAVE_WIN32_API
@@ -85,6 +93,7 @@ typedef struct H5FD_core_t {
 #endif /* H5_HAVE_WIN32_API */
     hbool_t dirty;                              /* changes not saved?       */
     H5FD_file_image_callbacks_t fi_callbacks;   /* file image callbacks     */
+    H5SL_t *dirty_list;                         /* dirty parts of the file  */
 } H5FD_core_t;
 
 /* Driver-specific file access properties */
@@ -96,6 +105,9 @@ typedef struct H5FD_core_fapl_t {
 /* Allocate memory in multiples of this size by default */
 #define H5FD_CORE_INCREMENT 8192
 
+/* Define the block size for aggregation */
+//#define H5FD_CORE_BLOCK_SIZE 524288 /* 512 K */
+
 /* These macros check for overflow of various quantities.  These macros
  * assume that file_offset_t is signed and haddr_t and size_t are unsigned.
  *
@@ -117,6 +129,9 @@ typedef struct H5FD_core_fapl_t {
                                 (size_t)((A)+(Z))<(size_t)(A))
 
 /* Prototypes */
+static herr_t H5FD_core_add_dirty_region(H5FD_core_t *file, haddr_t start, haddr_t end);
+static herr_t H5FD_core_destroy_dirty_list(H5FD_core_t *file);
+static herr_t H5FD_core_write_to_bstore(H5FD_core_t *file, haddr_t addr, size_t size);
 static herr_t H5FD_core_term(void);
 static void *H5FD_core_fapl_get(H5FD_t *_file);
 static H5FD_t *H5FD_core_open(const char *name, unsigned flags, hid_t fapl_id,
@@ -170,6 +185,256 @@ static const H5FD_class_t H5FD_core_g = {
     H5FD_FLMAP_DICHOTOMY        /* fl_map               */
 };
 
+/* Define a free list to manage the region type */
+H5FL_DEFINE(H5FD_core_region_t);
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_core_add_dirty_region
+ *
+ * Purpose:     Add a new dirty region to the list for later flushing
+ *              to the backing store.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_core_add_dirty_region(H5FD_core_t *file, haddr_t start, haddr_t end)
+{
+    H5FD_core_region_t *b_item  = NULL;
+    H5FD_core_region_t *a_item  = NULL;
+    H5FD_core_region_t *item    = NULL;
+    haddr_t     b_addr          = 0;
+    haddr_t     a_addr          = 0;
+    hbool_t     create_new_node = TRUE;
+    herr_t      ret_value       = SUCCEED;
+#ifdef DER
+    hbool_t     was_adjusted    = FALSE;
+#endif
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    HDassert(file);
+    HDassert(file->dirty_list);
+    HDassert(start <= end);
+
+#ifdef DER
+fprintf(stderr, "Add region: (%llu, %llu)\n", start, end);
+#endif
+
+//    /* Adjust the dirty region to the nearest block boundaries */
+//    if(start % H5FD_CORE_BLOCK_SIZE != 0) {
+//        start = (start / H5FD_CORE_BLOCK_SIZE) * H5FD_CORE_BLOCK_SIZE;
+    /* Adjust the dirty region to the nearest block boundaries */
+    if(start % file->bstore_page_size != 0) {
+        start = (start / file->bstore_page_size) * file->bstore_page_size;
+#ifdef DER
+        was_adjusted = TRUE;
+#endif
+    }
+//    if(end % H5FD_CORE_BLOCK_SIZE != (H5FD_CORE_BLOCK_SIZE - 1)) {
+//        end = (((end / H5FD_CORE_BLOCK_SIZE) + 1) * H5FD_CORE_BLOCK_SIZE) - 1;
+    if(end % file->bstore_page_size != (file->bstore_page_size - 1)) {
+        end = (((end / file->bstore_page_size) + 1) * file->bstore_page_size) - 1;
+        if(end > file->eof){
+#ifdef DER
+fprintf(stderr, "Adjusted to EOF\n");
+#endif
+            end = file->eof - 1;
+        }
+#ifdef DER
+        was_adjusted = TRUE;
+#endif
+    }
+
+#ifdef DER
+if(was_adjusted)
+    fprintf(stderr, "Adjusted region: (%llu, %llu)\n", start, end);
+#endif
+
+    /* Get the regions before and after the intended insertion point */
+    b_addr = start +1;
+    a_addr = end + 2;
+    b_item = (H5FD_core_region_t *)H5SL_less(file->dirty_list, &b_addr);
+    a_item = (H5FD_core_region_t *)H5SL_less(file->dirty_list, &a_addr);
+
+    /* Check to see if we need to extend the upper end of the NEW region */
+    if(a_item) {
+        if(start < a_item->start && end < a_item->end) {
+
+            /* Extend the end of the NEW region to match the existing AFTER region */
+            end = a_item->end;
+        }
+    }
+    /* Attempt to extend the PREV region */
+    if(b_item) {
+        if(start <= b_item->end + 1) {
+
+            /* Need to set this for the delete algorithm */
+            start = b_item->start;
+
+            /* We won't need to insert a new node since we can
+             * just update an existing one instead.
+             */
+            create_new_node = FALSE;
+        }
+    }
+
+    /* Remove any old nodes that are no longer needed */
+    while(a_item && a_item->start > start) {
+
+        H5FD_core_region_t *less;
+        haddr_t key = a_item->start - 1;
+
+        /* Save the previous node before we trash this one */
+        less = (H5FD_core_region_t *)H5SL_less(file->dirty_list, &key);
+
+        /* Delete this node */
+        a_item = (H5FD_core_region_t *)H5SL_remove(file->dirty_list, &a_item->start);
+        a_item = H5FL_FREE(H5FD_core_region_t, a_item);
+
+        /* Set up to check the next node */
+        if(less)
+            a_item = less;
+    }
+
+    /* Insert the new node */
+    if(create_new_node) {
+        if(NULL == (item = (H5FD_core_region_t *)H5SL_search(file->dirty_list, &start))) {
+            /* Ok to insert.  No pre-existing node with that key. */
+            item = (H5FD_core_region_t *)H5FL_CALLOC(H5FD_core_region_t);
+            item->start = start;
+            item->end = end;
+            if(H5SL_insert(file->dirty_list, item, &item->start) < 0)
+                HGOTO_ERROR(H5E_SLIST, H5E_CANTINSERT, FAIL, "can't insert new dirty region: (%llu, %llu)\n", start, end)
+        }
+        else {
+            /* Store the new item endpoint if it's bigger */
+            item->end = (item->end < end) ? end : item->end;
+        }
+    }
+    else {
+        /* Update the size of the before region */
+        if(b_item->end < end)
+            b_item->end = end;
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5FD_core_add_dirty_region() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_core_destroy_dirty_list
+ *
+ * Purpose:     Completely destroy the dirty list.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_core_destroy_dirty_list(H5FD_core_t *file)
+{
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    HDassert(file);
+
+    /* Destroy the list, including any remaining list elements */
+    if(file->dirty_list) {
+        H5FD_core_region_t *region = NULL;
+
+#ifdef DER
+{
+size_t count = H5SL_count(file->dirty_list);
+if(count != 0)
+    fprintf(stderr, "LIST NOT EMPTY AT DESTROY\n");
+}
+#endif
+        while(NULL != (region = (H5FD_core_region_t *)H5SL_remove_first(file->dirty_list)))
+            region = H5FL_FREE(H5FD_core_region_t, region);
+
+        if(H5SL_close(file->dirty_list) < 0)
+            HGOTO_ERROR(H5E_SLIST, H5E_CLOSEERROR, FAIL, "can't close core vfd dirty list")
+        file->dirty_list = NULL;
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5FD_core_destroy_dirty_list() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_core_write_to_bstore
+ *
+ * Purpose:     Write data to the backing store.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t H5FD_core_write_to_bstore(H5FD_core_t *file, haddr_t addr, size_t size)
+{
+    unsigned char  *ptr         = file->mem + addr;     /* mutable pointer into the
+                                                         * buffer (can't change mem)
+                                                         */
+    herr_t          ret_value   = SUCCEED;              /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    HDassert(file);
+
+    /* Write to backing store */
+    if((off_t)addr != HDlseek(file->fd, (off_t)addr, SEEK_SET))
+        HGOTO_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "error seeking in backing store")
+
+    while (size > 0) {
+
+        h5_posix_io_t       bytes_in        = 0;    /* # of bytes to write  */
+        h5_posix_io_ret_t   bytes_wrote     = -1;   /* # of bytes written   */
+
+        /* Trying to write more bytes than the return type can handle is
+         * undefined behavior in POSIX.
+         */
+        if(size > H5_POSIX_MAX_IO_BYTES)
+            bytes_in = H5_POSIX_MAX_IO_BYTES;
+        else
+            bytes_in = (h5_posix_io_t)size;
+
+#ifdef DER
+fprintf(stderr, "\nNEW\n");
+#endif
+        do {
+            bytes_wrote = HDwrite(file->fd, ptr, bytes_in);
+#ifdef DER
+fprintf(stderr, "bytes wrote: %lu\n", bytes_wrote);
+#endif
+        } while(-1 == bytes_wrote && EINTR == errno);
+
+        if(-1 == bytes_wrote) { /* error */
+            int myerrno = errno;
+            time_t mytime = HDtime(NULL);
+            HDoff_t myoffset = HDlseek(file->fd, (HDoff_t)0, SEEK_CUR);
+
+            HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "write to backing store failed: time = %s, filename = '%s', file descriptor = %d, errno = %d, error message = '%s', ptr = %p, total write size = %llu, bytes this sub-write = %llu, bytes actually written = %llu, offset = %llu", HDctime(&mytime), file->name, file->fd, myerrno, HDstrerror(myerrno), ptr, (unsigned long long)size, (unsigned long long)bytes_in, (unsigned long long)bytes_wrote, (unsigned long long)myoffset);
+        } /* end if */
+
+        HDassert(bytes_wrote > 0);
+        HDassert((size_t)bytes_wrote <= size);
+
+        size -= (size_t)bytes_wrote;
+        ptr = (unsigned char *)ptr + bytes_wrote;
+
+    } /* end while */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5FD_core_write_to_bstore() */
+
 
 /*-------------------------------------------------------------------------
  * Function:    H5FD_core_init_interface
@@ -566,6 +831,40 @@ H5FD_core_open(const char *name, unsigned flags, hid_t fapl_id, haddr_t maxaddr)
         } /* end if */
     } /* end if */
 
+    /* Set up write tracking if the backing store is on */
+    file->dirty_list = NULL;
+    if(fa->backing_store) {
+        hbool_t write_tracking_flag = FALSE;    /* what the user asked for */
+        hbool_t use_write_tracking = FALSE;     /* what we're actually doing */
+
+        /* Get the write tracking flag */
+        if(H5P_get(plist, H5F_ACS_CORE_WRITE_TRACKING_FLAG_NAME, &write_tracking_flag) < 0)
+            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, NULL, "can't get core VFD write tracking flag");
+
+        /* Get the page size */
+        if(H5P_get(plist, H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_NAME, &(file->bstore_page_size)) < 0)
+            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, NULL, "can't get core VFD write tracking page size");
+
+        /* default is to have write tracking OFF for create (hence the check to see
+         * if the user explicitly set a page size) and ON with the default page size
+         * on open (when not read-only).
+         */
+        /* Only use write tracking if the file is open for writing */
+        use_write_tracking = 
+            TRUE == write_tracking_flag         /* user asked for write tracking */
+            && !(o_flags & O_RDONLY)            /* file is open for writing (i.e. not read-only) */
+            && file->bstore_page_size != 0;     /* page size is not zero */
+
+        /* initialize the dirty list */
+        if(use_write_tracking) {
+            if(NULL == (file->dirty_list = H5SL_create(H5SL_TYPE_HADDR, NULL)))
+                HGOTO_ERROR(H5E_SLIST, H5E_CANTCREATE, NULL, "can't create core vfd dirty region list");
+#ifdef DER
+fprintf(stderr, "\n");
+#endif
+        } /* end if */
+    } /* end if */
+
     /* Set return value */
     ret_value = (H5FD_t *)file;
 
@@ -604,7 +903,12 @@ H5FD_core_close(H5FD_t *_file)
 
     /* Flush any changed buffers */
     if(H5FD_core_flush(_file, (hid_t)-1, TRUE) < 0)
-        HGOTO_ERROR(H5E_FILE, H5E_CANTFLUSH, FAIL, "unable to flush file")
+        HGOTO_ERROR(H5E_FILE, H5E_CANTFLUSH, FAIL, "unable to flush core vfd backing store")
+
+    /* Destroy the dirty region list */
+    if(file->dirty_list)
+        if(H5FD_core_destroy_dirty_list(file) != SUCCEED)
+            HGOTO_ERROR(H5E_VFL, H5E_CANTFREE, FAIL, "unable to free core vfd dirty region list")
 
     /* Release resources */
     if(file->fd >= 0)
@@ -1025,6 +1329,14 @@ H5FD_core_write(H5FD_t *_file, H5FD_mem_t UNUSED type, hid_t UNUSED dxpl_id, had
         file->eof = new_eof;
     } /* end if */
 
+    /* Add the buffer region to the dirty list if using that optimization */
+    if(file->dirty_list) {
+        haddr_t start = addr;
+        haddr_t end = addr + (haddr_t)size - 1;
+        if(H5FD_core_add_dirty_region(file, start, end) != SUCCEED)
+            HGOTO_ERROR(H5E_VFL, H5E_CANTINSERT, FAIL, "unable to add core VFD dirty region during write call - addresses: start=%llu end=%llu", start, end)
+    }
+
     /* Write from BUF to memory */
     HDmemcpy(file->mem + addr, buf, size);
 
@@ -1059,45 +1371,41 @@ H5FD_core_flush(H5FD_t *_file, hid_t UNUSED dxpl_id, unsigned UNUSED closing)
 
     /* Write to backing store */
     if (file->dirty && file->fd >= 0 && file->backing_store) {
-        haddr_t size = file->eof;
-        unsigned char *ptr = file->mem;
-
-        if(0 != HDlseek(file->fd, (off_t)0, SEEK_SET))
-            HGOTO_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "error seeking in backing store")
-        
-        while (size > 0) {
 
-            h5_posix_io_t       bytes_in        = 0;    /* # of bytes to write  */
-            h5_posix_io_ret_t   bytes_wrote     = -1;   /* # of bytes written   */ 
+        /* Use the dirty list, if available */
+        if(file->dirty_list) {
+            H5FD_core_region_t *item = NULL;
+            size_t size;
 
-            /* Trying to write more bytes than the return type can handle is
-             * undefined behavior in POSIX.
-             */
-            if(size > H5_POSIX_MAX_IO_BYTES)
-                bytes_in = H5_POSIX_MAX_IO_BYTES;
-            else
-                bytes_in = (h5_posix_io_t)size;
-
-            do {
-                bytes_wrote = HDwrite(file->fd, ptr, bytes_in);
-            } while(-1 == bytes_wrote && EINTR == errno);
-            
-            if(-1 == bytes_wrote) { /* error */
-                int myerrno = errno;
-                time_t mytime = HDtime(NULL);
-                HDoff_t myoffset = HDlseek(file->fd, (HDoff_t)0, SEEK_CUR);
-
-                HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "write to backing store failed: time = %s, filename = '%s', file descriptor = %d, errno = %d, error message = '%s', ptr = %p, total write size = %llu, bytes this sub-write = %llu, bytes actually written = %llu, offset = %llu", HDctime(&mytime), file->name, file->fd, myerrno, HDstrerror(myerrno), ptr, (unsigned long long)size, (unsigned long long)bytes_in, (unsigned long long)bytes_wrote, (unsigned long long)myoffset);
-            } /* end if */
-            
-            HDassert(bytes_wrote > 0);
-            HDassert((size_t)bytes_wrote <= size);
+#ifdef DER
+    fprintf(stderr, "FLUSHING. DIRTY LIST:\n");
+#endif
+            while(NULL != (item = (H5FD_core_region_t *)H5SL_remove_first(file->dirty_list))) {
+                size = (size_t)((item->end - item->start) + 1);
+#ifdef DER
+fprintf(stderr, "(%llu, %llu : %lu)\n", item->start, item->end, size);
+#endif
+                if(H5FD_core_write_to_bstore(file, item->start, size) != SUCCEED)
+                    HGOTO_ERROR(H5E_VFL, H5E_WRITEERROR, FAIL, "unable to write to backing store")
+                item = H5FL_FREE(H5FD_core_region_t, item);
+            }
+
+ 
+#ifdef DER
+fprintf(stderr, "EOF: %llu\n", file->eof);
+fprintf(stderr, "EOA: %llu\n", file->eoa);
+if(file->eoa > file->eof)
+    fprintf(stderr, "*** EOA BADNESS ***\n");
+fprintf(stderr, "\n");
+#endif
+        }
+        /* Otherwise, write the entire file out at once */
+        else {
+            if(H5FD_core_write_to_bstore(file, (haddr_t)0, (size_t)file->eof) != SUCCEED)
+                HGOTO_ERROR(H5E_VFL, H5E_WRITEERROR, FAIL, "unable to write to backing store")
 
-            size -= (size_t)bytes_wrote;
-            ptr = (unsigned char *)ptr + bytes_wrote;
-            
         } /* end while */
-        
+
         file->dirty = FALSE;
     }
 
@@ -1221,6 +1529,10 @@ H5FD_core_truncate(H5FD_t *_file, hid_t UNUSED dxpl_id, hbool_t closing)
                 if(-1 == HDftruncate(file->fd, (HDoff_t)new_eof))
                     HSYS_GOTO_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "unable to extend file properly")
 #endif /* H5_HAVE_WIN32_API */
+
+#ifdef DER
+fprintf(stderr, "OLD: Truncated to: %llu\n", file->eoa);
+#endif
             } /* end if */
 
             /* Update the eof value */
@@ -1231,3 +1543,4 @@ H5FD_core_truncate(H5FD_t *_file, hid_t UNUSED dxpl_id, hbool_t closing)
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5FD_core_truncate() */
+
diff --git a/src/H5Fprivate.h b/src/H5Fprivate.h
index 2690311..cfecf98 100644
--- a/src/H5Fprivate.h
+++ b/src/H5Fprivate.h
@@ -462,6 +462,8 @@ typedef struct H5F_blk_aggr_t H5F_blk_aggr_t;
 #define H5F_ACS_WANT_POSIX_FD_NAME              "want_posix_fd" /* Internal: query the file descriptor from the core VFD, instead of the memory address */
 #define H5F_ACS_EFC_SIZE_NAME                   "efc_size"      /* Size of external file cache */
 #define H5F_ACS_FILE_IMAGE_INFO_NAME            "file_image_info" /* struct containing initial file image and callback info */
+#define H5F_ACS_CORE_WRITE_TRACKING_FLAG_NAME       "core_write_tracking_flag" /* Whether or not core VFD backing store write tracking is enabled */
+#define H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_NAME  "core_write_tracking_page_size" /* The page size in kiB when core VFD write tracking is enabled */
 
 /* ======================== File Mount properties ====================*/
 #define H5F_MNT_SYM_LOCAL_NAME 		"local"                 /* Whether absolute symlinks local to file. */
diff --git a/src/H5Pfapl.c b/src/H5Pfapl.c
index a4c09e5..c217acb 100644
--- a/src/H5Pfapl.c
+++ b/src/H5Pfapl.c
@@ -160,7 +160,16 @@
 #define H5F_ACS_FILE_IMAGE_INFO_DEL             H5P_file_image_info_del
 #define H5F_ACS_FILE_IMAGE_INFO_COPY            H5P_file_image_info_copy
 #define H5F_ACS_FILE_IMAGE_INFO_CLOSE           H5P_file_image_info_close
-
+/* Definition of core VFD write tracking flag */
+#define H5F_ACS_CORE_WRITE_TRACKING_FLAG_SIZE   sizeof(hbool_t)
+#define H5F_ACS_CORE_WRITE_TRACKING_FLAG_DEF    FALSE
+#define H5F_ACS_CORE_WRITE_TRACKING_FLAG_ENC    H5P__encode_hbool_t
+#define H5F_ACS_CORE_WRITE_TRACKING_FLAG_DEC    H5P__decode_hbool_t
+/* Definition of core VFD write tracking page size */
+#define H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_SIZE      sizeof(size_t)
+#define H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_DEF       524288
+#define H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_ENC       H5P__encode_size_t
+#define H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_DEC       H5P__decode_size_t
 
 /******************/
 /* Local Typedefs */
@@ -246,8 +255,9 @@ static const H5FD_mem_t H5F_def_mem_type_g = H5F_ACS_MULTI_TYPE_DEF;
 static const hbool_t H5F_def_latest_format_g = H5F_ACS_LATEST_FORMAT_DEF;          /* Default setting for "use the latest version of the format" flag */
 static const hbool_t H5F_def_want_posix_fd_g = H5F_ACS_WANT_POSIX_FD_DEF;          /* Default setting for retrieving 'handle' from core VFD */
 static const unsigned H5F_def_efc_size_g = H5F_ACS_EFC_SIZE_DEF;                   /* Default external file cache size */
-static const H5FD_file_image_info_t H5F_def_file_image_info_g = H5F_ACS_FILE_IMAGE_INFO_DEF;  /* Default file image info and callbacks */
-
+static const H5FD_file_image_info_t H5F_def_file_image_info_g = H5F_ACS_FILE_IMAGE_INFO_DEF;                 /* Default file image info and callbacks */
+static const hbool_t H5F_def_core_write_tracking_flag_g = H5F_ACS_CORE_WRITE_TRACKING_FLAG_DEF;              /* Default setting for core VFD write tracking */
+static const size_t H5F_def_core_write_tracking_page_size_g = H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_DEF;     /* Default core VFD write tracking page size */
 
 
 /*-------------------------------------------------------------------------
@@ -397,6 +407,18 @@ H5P_facc_reg_prop(H5P_genclass_t *pclass)
             H5F_ACS_FILE_IMAGE_INFO_DEL, H5F_ACS_FILE_IMAGE_INFO_COPY, NULL, H5F_ACS_FILE_IMAGE_INFO_CLOSE) < 0)
         HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
 
+    /* Register the core VFD backing store write tracking flag */
+    if(H5P_register_real(pclass, H5F_ACS_CORE_WRITE_TRACKING_FLAG_NAME, H5F_ACS_CORE_WRITE_TRACKING_FLAG_SIZE, &H5F_def_core_write_tracking_flag_g , 
+            NULL, NULL, NULL, H5F_ACS_CORE_WRITE_TRACKING_FLAG_ENC, H5F_ACS_CORE_WRITE_TRACKING_FLAG_DEC, 
+            NULL, NULL, NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
+
+    /* Register the size of the core VFD backing store page size */
+    if(H5P_register_real(pclass, H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_NAME, H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_SIZE, &H5F_def_core_write_tracking_page_size_g , 
+            NULL, NULL, NULL, H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_ENC, H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_DEC, 
+            NULL, NULL, NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
+
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5P_facc_reg_prop() */
@@ -2980,3 +3002,76 @@ H5P__facc_multi_type_dec(const void **_pp, void *_value)
     FUNC_LEAVE_NOAPI(SUCCEED)
 } /* end H5P__facc_multi_type_dec() */
 
+
+/*-------------------------------------------------------------------------
+ * Function:	H5Pset_core_write_tracking
+ *
+ * Purpose:	Enables/disables core VFD write tracking and page
+ *              aggregation size.
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pset_core_write_tracking(hid_t plist_id, hbool_t is_enabled, size_t page_size)
+{
+    H5P_genplist_t *plist;        /* Property list pointer */
+    herr_t ret_value = SUCCEED;   /* return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE3("e", "ibz", plist_id, is_enabled, page_size);
+
+    /* Get the plist structure */
+    if(NULL == (plist = H5P_object_verify(plist_id, H5P_FILE_ACCESS)))
+        HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL, "can't find object for ID")
+
+    /* Set values */
+    if(H5P_set(plist, H5F_ACS_CORE_WRITE_TRACKING_FLAG_NAME, &is_enabled) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set core VFD write tracking flag")
+    if(H5P_set(plist, H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_NAME, &page_size) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set core VFD write tracking page size")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+}
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5Pget_core_write_tracking
+ *
+ * Purpose:	Gets information about core VFD write tracking and page
+ *              aggregation size.
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pget_core_write_tracking(hid_t plist_id, hbool_t *is_enabled, size_t *page_size)
+{
+    H5P_genplist_t *plist;      /* Property list pointer */
+    herr_t ret_value = SUCCEED;   /* return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE3("e", "i*b*z", plist_id, is_enabled, page_size);
+
+    /* Get the plist structure */
+    if(NULL == (plist = H5P_object_verify(plist_id, H5P_FILE_ACCESS)))
+        HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL, "can't find object for ID")
+
+    /* Get values */
+    if(is_enabled) {
+        if(H5P_get(plist, H5F_ACS_CORE_WRITE_TRACKING_FLAG_NAME, is_enabled) < 0)
+            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get core VFD write tracking flag")
+    } /* end if */
+
+    if(page_size) {
+        if(H5P_get(plist, H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_NAME, page_size) < 0)
+            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get core VFD write tracking page size")
+    } /* end if */
+
+done:
+    FUNC_LEAVE_API(ret_value)
+}
+
diff --git a/src/H5Ppublic.h b/src/H5Ppublic.h
index d35f4da..fd5ff5f 100644
--- a/src/H5Ppublic.h
+++ b/src/H5Ppublic.h
@@ -296,7 +296,6 @@ H5_DLL herr_t H5Pget_shared_mesg_phase_change(hid_t plist_id, unsigned *max_list
 H5_DLL herr_t H5Pset_file_space(hid_t plist_id, H5F_file_space_type_t strategy, hsize_t threshold);
 H5_DLL herr_t H5Pget_file_space(hid_t plist_id, H5F_file_space_type_t *strategy, hsize_t *threshold);
 
-
 /* File access property list (FAPL) routines */
 H5_DLL herr_t H5Pset_alignment(hid_t fapl_id, hsize_t threshold,
     hsize_t alignment);
@@ -344,6 +343,9 @@ H5_DLL herr_t H5Pset_file_image_callbacks(hid_t fapl_id,
 H5_DLL herr_t H5Pget_file_image_callbacks(hid_t fapl_id,
        H5FD_file_image_callbacks_t *callbacks_ptr);
 
+H5_DLL herr_t H5Pset_core_write_tracking(hid_t fapl_id, hbool_t is_enabled, size_t page_size);
+H5_DLL herr_t H5Pget_core_write_tracking(hid_t fapl_id, hbool_t *is_enabled, size_t *page_size);
+
 /* Dataset creation property list (DCPL) routines */
 H5_DLL herr_t H5Pset_layout(hid_t plist_id, H5D_layout_t layout);
 H5_DLL H5D_layout_t H5Pget_layout(hid_t plist_id);
diff --git a/test/Makefile.am b/test/Makefile.am
index 6938133..b5ebcf3 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -103,7 +103,7 @@ LDADD=libh5test.la $(LIBHDF5)
 ttsafe_SOURCES=ttsafe.c ttsafe_dcreate.c ttsafe_error.c ttsafe_cancel.c       \
                ttsafe_acreate.c
 
-VFD_LIST = sec2 stdio core split multi family
+VFD_LIST = sec2 stdio core core_paged split multi family
 if DIRECT_VFD_CONDITIONAL
   VFD_LIST += direct
 endif
diff --git a/test/Makefile.in b/test/Makefile.in
index 628b004..16071a8 100644
--- a/test/Makefile.in
+++ b/test/Makefile.in
@@ -1155,7 +1155,8 @@ LDADD = libh5test.la $(LIBHDF5)
 ttsafe_SOURCES = ttsafe.c ttsafe_dcreate.c ttsafe_error.c ttsafe_cancel.c       \
                ttsafe_acreate.c
 
-VFD_LIST = sec2 stdio core split multi family $(am__append_4)
+VFD_LIST = sec2 stdio core core_paged split multi family \
+	$(am__append_4)
 
 # Sources for testhdf5 executable
 testhdf5_SOURCES = testhdf5.c tarray.c tattr.c tchecksum.c tconfig.c tfile.c \
diff --git a/test/enc_dec_plist.c b/test/enc_dec_plist.c
index 2d0d732..422ad1b 100644
--- a/test/enc_dec_plist.c
+++ b/test/enc_dec_plist.c
@@ -381,6 +381,8 @@ main(void)
         FAIL_STACK_ERROR
     if((H5Pset_mdc_config(fapl, &my_cache_config)) < 0)
         FAIL_STACK_ERROR
+    if((H5Pset_core_write_tracking(fapl, TRUE, 1024 * 1024)) < 0)
+        FAIL_STACK_ERROR
 
     /* Test encoding & decoding property list */
     if(test_encode_decode(fapl) < 0)
diff --git a/test/gen_plist.c b/test/gen_plist.c
index b4da261..acc5f3e 100644
--- a/test/gen_plist.c
+++ b/test/gen_plist.c
@@ -327,6 +327,8 @@ main(void)
         assert(ret > 0);
     if((ret = H5Pset_mdc_config(fapl1, &my_cache_config)) < 0)
         assert(ret > 0);
+    if((ret = H5Pset_core_write_tracking(fapl1, TRUE, (size_t)(1024 * 1024))) < 0)
+        assert(ret > 0);
 
     if((ret = encode_plist(fapl1, little_endian, "testfiles/plist_files/fapl_le", "testfiles/plist_files/fapl_be")) < 0)
         assert(ret > 0);
diff --git a/test/h5test.c b/test/h5test.c
index 9fe05ae..769e03f 100644
--- a/test/h5test.c
+++ b/test/h5test.c
@@ -511,64 +511,71 @@ h5_fileaccess(void)
     /* First use the environment variable, then the constant */
     val = HDgetenv("HDF5_DRIVER");
 #ifdef HDF5_DRIVER
-    if (!val) val = HDF5_DRIVER;
+    if (!val)
+        val = HDF5_DRIVER;
 #endif
 
-    if ((fapl=H5Pcreate(H5P_FILE_ACCESS))<0) return -1;
-    if (!val || !*val) return fapl; /*use default*/
+    if ((fapl=H5Pcreate(H5P_FILE_ACCESS))<0)
+        return -1;
+    if (!val || !*val)
+        return fapl; /*use default*/
 
     HDstrncpy(s, val, sizeof s);
     s[sizeof(s)-1] = '\0';
     if (NULL==(name=HDstrtok(s, " \t\n\r"))) return fapl;
 
     if (!HDstrcmp(name, "sec2")) {
-  /* Unix read() and write() system calls */
-  if (H5Pset_fapl_sec2(fapl)<0) return -1;
+        /* Unix read() and write() system calls */
+        if (H5Pset_fapl_sec2(fapl)<0) return -1;
     } else if (!HDstrcmp(name, "stdio")) {
-  /* Standard C fread() and fwrite() system calls */
-  if (H5Pset_fapl_stdio(fapl)<0) return -1;
+        /* Standard C fread() and fwrite() system calls */
+        if (H5Pset_fapl_stdio(fapl)<0) return -1;
     } else if (!HDstrcmp(name, "core")) {
-  /* In-core temporary file with 1MB increment */
-  if (H5Pset_fapl_core(fapl, (size_t)1, TRUE)<0) return -1;
-    } else if (!HDstrcmp(name, "split")) {
-  /* Split meta data and raw data each using default driver */
-  if (H5Pset_fapl_split(fapl,
+        /* In-memory driver settings (backing store on, 1 MB increment) */
+        if (H5Pset_fapl_core(fapl, (size_t)1, TRUE)<0) return -1;
+    } else if (!HDstrcmp(name, "core_paged")) {
+        /* In-memory driver with write tracking and paging on */
+        if (H5Pset_fapl_core(fapl, (size_t)1, TRUE)<0) return -1;
+        if (H5Pset_core_write_tracking(fapl, TRUE, (size_t)4096)<0) return -1;
+     } else if (!HDstrcmp(name, "split")) {
+        /* Split meta data and raw data each using default driver */
+        if (H5Pset_fapl_split(fapl,
             "-m.h5", H5P_DEFAULT,
             "-r.h5", H5P_DEFAULT)<0)
-      return -1;
+            return -1;
     } else if (!HDstrcmp(name, "multi")) {
-  /* Multi-file driver, general case of the split driver */
-  H5FD_mem_t memb_map[H5FD_MEM_NTYPES];
-  hid_t memb_fapl[H5FD_MEM_NTYPES];
-  const char *memb_name[H5FD_MEM_NTYPES];
-  char sv[H5FD_MEM_NTYPES][1024];
-  haddr_t memb_addr[H5FD_MEM_NTYPES];
+        /* Multi-file driver, general case of the split driver */
+        H5FD_mem_t memb_map[H5FD_MEM_NTYPES];
+        hid_t memb_fapl[H5FD_MEM_NTYPES];
+        const char *memb_name[H5FD_MEM_NTYPES];
+        char sv[H5FD_MEM_NTYPES][1024];
+        haddr_t memb_addr[H5FD_MEM_NTYPES];
         H5FD_mem_t  mt;
 
-  HDmemset(memb_map, 0, sizeof memb_map);
-  HDmemset(memb_fapl, 0, sizeof memb_fapl);
-  HDmemset(memb_name, 0, sizeof memb_name);
-  HDmemset(memb_addr, 0, sizeof memb_addr);
-
-  HDassert(HDstrlen(multi_letters)==H5FD_MEM_NTYPES);
-  for(mt = H5FD_MEM_DEFAULT; mt < H5FD_MEM_NTYPES; H5_INC_ENUM(H5FD_mem_t, mt)) {
-      memb_fapl[mt] = H5P_DEFAULT;
-      sprintf(sv[mt], "%%s-%c.h5", multi_letters[mt]);
-      memb_name[mt] = sv[mt];
-      memb_addr[mt] = (haddr_t)MAX(mt - 1, 0) * (HADDR_MAX / 10);
-  } /* end for */
-
-  if (H5Pset_fapl_multi(fapl, memb_map, memb_fapl, memb_name,
-            memb_addr, FALSE)<0) {
-      return -1;
-  }
+        HDmemset(memb_map, 0, sizeof memb_map);
+        HDmemset(memb_fapl, 0, sizeof memb_fapl);
+        HDmemset(memb_name, 0, sizeof memb_name);
+        HDmemset(memb_addr, 0, sizeof memb_addr);
+
+        HDassert(HDstrlen(multi_letters)==H5FD_MEM_NTYPES);
+        for(mt = H5FD_MEM_DEFAULT; mt < H5FD_MEM_NTYPES; H5_INC_ENUM(H5FD_mem_t, mt)) {
+          memb_fapl[mt] = H5P_DEFAULT;
+            sprintf(sv[mt], "%%s-%c.h5", multi_letters[mt]);
+            memb_name[mt] = sv[mt];
+            memb_addr[mt] = (haddr_t)MAX(mt - 1, 0) * (HADDR_MAX / 10);
+        } /* end for */
+
+        if (H5Pset_fapl_multi(fapl, memb_map, memb_fapl, memb_name,
+          memb_addr, FALSE)<0) {
+            return -1;
+        }
     } else if (!HDstrcmp(name, "family")) {
         hsize_t fam_size = 100*1024*1024; /*100 MB*/
 
-  /* Family of files, each 1MB and using the default driver */
-  if ((val=HDstrtok(NULL, " \t\n\r")))
-      fam_size = (hsize_t)(HDstrtod(val, NULL) * 1024*1024);
-  if (H5Pset_fapl_family(fapl, fam_size, H5P_DEFAULT)<0)
+        /* Family of files, each 1MB and using the default driver */
+        if ((val=HDstrtok(NULL, " \t\n\r")))
+            fam_size = (hsize_t)(HDstrtod(val, NULL) * 1024*1024);
+        if (H5Pset_fapl_family(fapl, fam_size, H5P_DEFAULT)<0)
             return -1;
     } else if (!HDstrcmp(name, "log")) {
         unsigned log_flags = H5FD_LOG_LOC_IO | H5FD_LOG_ALLOC;
@@ -578,20 +585,21 @@ h5_fileaccess(void)
             log_flags = (unsigned)HDstrtol(val, NULL, 0);
 
         if (H5Pset_fapl_log(fapl, NULL, log_flags, (size_t)0) < 0)
-      return -1;
+            return -1;
     } else if (!HDstrcmp(name, "direct")) {
 #ifdef H5_HAVE_DIRECT
-  /* Linux direct read() and write() system calls.  Set memory boundary, file block size,
-   * and copy buffer size to the default values. */
-  if (H5Pset_fapl_direct(fapl, 1024, 4096, 8*4096)<0) return -1;
+        /* Linux direct read() and write() system calls.  Set memory boundary, file block size,
+         * and copy buffer size to the default values. */
+        if (H5Pset_fapl_direct(fapl, 1024, 4096, 8*4096)<0)
+            return -1;
 #endif
     } else if(!HDstrcmp(name, "latest")) {
-  /* use the latest format */
-  if(H5Pset_libver_bounds(fapl, H5F_LIBVER_LATEST, H5F_LIBVER_LATEST) < 0)
+        /* use the latest format */
+        if(H5Pset_libver_bounds(fapl, H5F_LIBVER_LATEST, H5F_LIBVER_LATEST) < 0)
             return -1;
     } else {
-  /* Unknown driver */
-  return -1;
+        /* Unknown driver */
+        return -1;
     }
 
     return fapl;
diff --git a/test/testfiles/plist_files/fapl_be b/test/testfiles/plist_files/fapl_be
index 8fcefa2..0b050d0 100644
--- a/test/testfiles/plist_files/fapl_be
+++ b/test/testfiles/plist_files/fapl_be
diff --git a/test/testfiles/plist_files/fapl_le b/test/testfiles/plist_files/fapl_le
index 8fcefa2..0b050d0 100644
--- a/test/testfiles/plist_files/fapl_le
+++ b/test/testfiles/plist_files/fapl_le
diff --git a/test/testfiles/plist_files/lapl_be b/test/testfiles/plist_files/lapl_be
index 30f52a4..e58bfb4 100644
--- a/test/testfiles/plist_files/lapl_be
+++ b/test/testfiles/plist_files/lapl_be
diff --git a/test/testfiles/plist_files/lapl_le b/test/testfiles/plist_files/lapl_le
index 30f52a4..e58bfb4 100644
--- a/test/testfiles/plist_files/lapl_le
+++ b/test/testfiles/plist_files/lapl_le
diff --git a/test/vfd.c b/test/vfd.c
index b85c054..4ece2ba 100644
--- a/test/vfd.c
+++ b/test/vfd.c
@@ -28,6 +28,7 @@
 #define FAMILY_SIZE2    (5*KB)
 #define MULTI_SIZE      128
 #define CORE_INCREMENT  (4*KB)
+#define CORE_PAGE_SIZE  (1024 * 1024)
 #define DSET1_NAME   "dset1"
 #define DSET1_DIM1   1024
 #define DSET1_DIM2   32
@@ -376,6 +377,8 @@ test_core(void)
     char        filename[1024];
     void        *fhandle=NULL;
     hsize_t     file_size;
+    hbool_t     use_write_tracking;
+    size_t      write_tracking_page_size;
     int    *points = NULL, *check = NULL, *p1, *p2;
     hid_t  dset1=-1, space1=-1;
     hsize_t  dims1[2];
@@ -387,6 +390,8 @@ test_core(void)
     fapl = h5_fileaccess();
     if(H5Pset_fapl_core(fapl, (size_t)CORE_INCREMENT, TRUE) < 0)
         TEST_ERROR;
+    if(H5Pset_core_write_tracking(fapl, TRUE, CORE_PAGE_SIZE) < 0)
+        TEST_ERROR;
     h5_fixname(FILENAME[1], fapl, filename, sizeof filename);
 
     if((file=H5Fcreate(filename, H5F_ACC_TRUNC, H5P_DEFAULT, fapl)) < 0)
@@ -400,6 +405,14 @@ test_core(void)
     if(H5FD_CORE != H5Pget_driver(access_fapl))
         TEST_ERROR;
 
+    /* Check that the backing store write tracking info was saved */
+    if(H5Pget_core_write_tracking(fapl, &use_write_tracking, &write_tracking_page_size) < 0)
+        TEST_ERROR;
+    if(TRUE != use_write_tracking)
+        TEST_ERROR;
+    if(CORE_PAGE_SIZE != write_tracking_page_size)
+        TEST_ERROR;
+
     /* ...and close the property list */
     if (H5Pclose(access_fapl) < 0)
         TEST_ERROR;