Preliminary checkins for implementation done so far:

1) Public routines: H5Pget/set_vfd_swmr_config
2) Public routine: H5Fvfd_swmr_end_tick
3) Initialization when opening a file with VFD SWMR writer
4) Tests in test/vfd_swmr.c for VFD SWMR
5) Fix a bug in src/H5Fint.c: when error is encountered after the root group is created
Note the following:
--This is WORK IN PROGRESS and will subject to change as implementation goes.
--There is test failure form enc_dec_plist.c: I will fix this when changes to the property list are settled.
--The branch is updated with the latest from develop as of 8/14/2018

17 files changed, 720 insertions, 9 deletions

diff --git a/src/H5.c b/src/H5.c
index 1b13fea..8ff8bdc 100644
--- a/src/H5.c
+++ b/src/H5.c
@@ -85,6 +85,12 @@ char                    H5_lib_vers_info_g[] = H5_VERS_INFO;
 static hbool_t          H5_dont_atexit_g = FALSE;
 H5_debug_t              H5_debug_g; /* debugging info */
 
+hbool_t vfd_swmr_g = FALSE;
+hbool_t vfd_swmr_writer_g = FALSE;
+uint64_t tick_num_g = 0;
+struct timespec end_of_tick_g;
+H5F_file_t *vfd_swmr_file_g;
+
 
 /*******************/
 /* Local Variables */
diff --git a/src/H5AC.c b/src/H5AC.c
index 989ee10..e6b1928 100644
--- a/src/H5AC.c
+++ b/src/H5AC.c
@@ -2760,7 +2760,7 @@ done:
  *------------------------------------------------------------------------------
  */
 herr_t
-H5AC_expunge_tag_type_metadata(H5F_t *f, haddr_t tag, int type_id, unsigned flags)
+H5AC_expunge_tag_type_metadata(H5F_t *f, haddr_t tag, int type_id, unsigned flags, hbool_t type_match)
 {
     /* Variable Declarations */
     herr_t ret_value = SUCCEED;
@@ -2773,7 +2773,7 @@ H5AC_expunge_tag_type_metadata(H5F_t *f, haddr_t tag, int type_id, unsigned flag
     HDassert(f->shared);
 
     /* Call cache level function to expunge entries with specified tag and type id */
-    if(H5C_expunge_tag_type_metadata(f, tag, type_id, flags)<0)
+    if(H5C_expunge_tag_type_metadata(f, tag, type_id, flags, type_match)<0)
         HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "Cannot expunge tagged type entries")
 
 done:
diff --git a/src/H5ACprivate.h b/src/H5ACprivate.h
index 99cc0e9..36872c4 100644
--- a/src/H5ACprivate.h
+++ b/src/H5ACprivate.h
@@ -444,7 +444,7 @@ H5_DLL void H5AC_set_ring(H5AC_ring_t ring, H5AC_ring_t *orig_ring);
 H5_DLL herr_t H5AC_unsettle_entry_ring(void *entry);
 H5_DLL herr_t H5AC_unsettle_ring(H5F_t * f, H5AC_ring_t ring);
 H5_DLL herr_t H5AC_expunge_tag_type_metadata(H5F_t *f, haddr_t tag, int type_id,
-    unsigned flags);
+    unsigned flags, hbool_t type_match);
 H5_DLL herr_t H5AC_get_tag(const void *thing, /*OUT*/ haddr_t *tag);
 
 /* Virtual entry routines */
diff --git a/src/H5Cprivate.h b/src/H5Cprivate.h
index 38a86ee..a3e46db 100644
--- a/src/H5Cprivate.h
+++ b/src/H5Cprivate.h
@@ -2246,7 +2246,7 @@ H5_DLL herr_t H5C_flush_cache(H5F_t *f, unsigned flags);
 H5_DLL herr_t H5C_flush_tagged_entries(H5F_t *f, haddr_t tag); 
 H5_DLL herr_t H5C_force_cache_image_load(H5F_t * f);
 H5_DLL herr_t H5C_evict_tagged_entries(H5F_t *f, haddr_t tag, hbool_t match_global);
-H5_DLL herr_t H5C_expunge_tag_type_metadata(H5F_t *f, haddr_t tag, int type_id, unsigned flags);
+H5_DLL herr_t H5C_expunge_tag_type_metadata(H5F_t *f, haddr_t tag, int type_id, unsigned flags, hbool_t type_match);
 H5_DLL herr_t H5C_get_tag(const void *thing, /*OUT*/ haddr_t *tag);
 #if H5C_DO_TAGGING_SANITY_CHECKS
 herr_t H5C_verify_tag(int id, haddr_t tag);
diff --git a/src/H5Ctag.c b/src/H5Ctag.c
index 66aedd9..16baac3 100644
--- a/src/H5Ctag.c
+++ b/src/H5Ctag.c
@@ -75,6 +75,7 @@ typedef struct {
     H5F_t *f;                           /* File pointer for evicting entry */
     int type_id;                        /* Cache entry type to expunge */
     unsigned flags;                     /* Flags for expunging entry */
+    hbool_t type_match;
 } H5C_tag_iter_ettm_ctx_t;
 
 /* Typedef for tagged entry iterator callback context - mark corked */
@@ -811,7 +812,7 @@ H5C__expunge_tag_type_metadata_cb(H5C_cache_entry_t *entry, void *_ctx)
     HDassert(ctx);
 
     /* Found one with the same tag and type id */
-    if(entry->type->id == ctx->type_id)
+    if(entry->type->id == ctx->type_id || !ctx->type_match)
         if(H5C_expunge_entry(ctx->f, entry->type, entry->addr, ctx->flags) < 0)
             HGOTO_ERROR(H5E_CACHE, H5E_CANTEXPUNGE, H5_ITER_ERROR, "can't expunge entry")
 
@@ -835,7 +836,7 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t 
-H5C_expunge_tag_type_metadata(H5F_t *f, haddr_t tag, int type_id, unsigned flags)
+H5C_expunge_tag_type_metadata(H5F_t *f, haddr_t tag, int type_id, unsigned flags, hbool_t type_match)
 {
     H5C_t *cache;                       /* Pointer to cache structure */
     H5C_tag_iter_ettm_ctx_t ctx;        /* Context for iterator callback */
@@ -855,6 +856,7 @@ H5C_expunge_tag_type_metadata(H5F_t *f, haddr_t tag, int type_id, unsigned flags
     ctx.f = f;
     ctx.type_id = type_id;
     ctx.flags = flags;
+    ctx.type_match = type_match;
 
     /* Iterate through hash table entries, expunge those with specified tag and type id */
     if(H5C__iter_tagged_entries(cache, tag, FALSE, H5C__expunge_tag_type_metadata_cb, &ctx) < 0)
diff --git a/src/H5Dint.c b/src/H5Dint.c
index e8874a2..21594c6 100644
--- a/src/H5Dint.c
+++ b/src/H5Dint.c
@@ -2986,7 +2986,7 @@ done:
                     HDONE_ERROR(H5E_DATASET, H5E_BADVALUE, FAIL, "address undefined")
 
                 /* Expunge from cache all v1 B-tree type entries associated with tag */
-                if(H5AC_expunge_tag_type_metadata(dataset->oloc.file, dataset->oloc.addr, H5AC_BT_ID, H5AC__NO_FLAGS_SET))
+                if(H5AC_expunge_tag_type_metadata(dataset->oloc.file, dataset->oloc.addr, H5AC_BT_ID, H5AC__NO_FLAGS_SET, TRUE))
                     HDONE_ERROR(H5E_DATASET, H5E_CANTEXPUNGE, FAIL, "unable to expunge index metadata")
             } /* end if */
 
diff --git a/src/H5F.c b/src/H5F.c
index 01fd7db..079af75 100644
--- a/src/H5F.c
+++ b/src/H5F.c
@@ -1713,3 +1713,35 @@ H5Fincrement_filesize(hid_t file_id, hsize_t increment)
 done:
     FUNC_LEAVE_API(ret_value)
 } /* H5Fincrement_filesize() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5Fvfd_swmr_end_tick()
+ *
+ * Purpose:     To allow user to trigger end of tick processing
+ *
+ * Return:      Non-negative on success/Negative on errors
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Fvfd_swmr_end_tick(hid_t file_id)
+{
+    H5F_t *file;                /* File object for file ID */
+    herr_t ret_value = SUCCEED; /* Return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE1("e", "i", file_id);
+
+    /* Check args */
+    if(NULL == (file = (H5F_t *)H5I_object_verify(file_id, H5I_FILE)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "hid_t identifier is not a file ID")
+
+    /* This will work only if the file is opened with VFD SWMR configured.*/
+    if(!(H5F_USE_VFD_SWMR(file)))
+        HGOTO_ERROR(H5E_FILE, H5E_BADVALUE, FAIL, "must have VFD SWMR configured for this public routine")
+
+    /* ??Trigger end of tick processing later */
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* H5Fvfd_swmr_end_tick() */
diff --git a/src/H5FDint.c b/src/H5FDint.c
index 023ff57..a26815e 100644
--- a/src/H5FDint.c
+++ b/src/H5FDint.c
@@ -418,3 +418,111 @@ H5FD_driver_query(const H5FD_class_t *driver, unsigned long *flags/*out*/)
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5FD_driver_query() */
 
+
+/*-------------------------------------------------------------------------
+* Function:    H5FD_writer_end_of_tick
+*
+* Purpose: 
+*
+* Return:  SUCCEED/FAIL
+*
+* Programmer:  
+*
+*-------------------------------------------------------------------------
+*/
+herr_t
+H5FD_writer_end_of_tick(void)
+{
+    herr_t ret_value = SUCCEED;          /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5FD_writer_end_of_tick() */
+
+
+/*-------------------------------------------------------------------------
+* Function:    H5FD_reader_end_of_tick
+*
+* Purpose: 
+*
+* Return:  SUCCEED/FAIL
+*
+* Programmer:  
+*
+*-------------------------------------------------------------------------
+*/
+herr_t
+H5FD_reader_end_of_tick(void)
+{
+    herr_t ret_value = SUCCEED;          /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5FD_reader_end_of_tick() */
+
+#ifdef OUT
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_vfd_swmr_md_read
+ *
+ * Purpose: 	??
+ *
+ * Return:      Success:        SUCCEED
+ *              Failure:        FAIL
+ *
+ * Programmer:  
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5FD_vfd_swmr_md_read(int md_fd, haddr_t addr, size_t size, const void *buf)
+{
+
+    HDlseek(fd, (HDoff_t)addr, SEEK_SET);
+    bytes_read = HDread(md_fd, buf, size);
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5FD_vfd_swmr_read() */
+
+herr_t
+H5FD_vfd_swmr_hdr_deserialize(int md_fd, size_t len)
+{
+    uint8_t image[H5FD_MD_HEADER_SIZE];   /* Buffer for element data */
+    uint8_t *p = NULL;
+    uint32_t fs_page_size;
+    uint64_t tick_num;
+    uint64_t index_offset;
+    uint64_t index_length;
+    uint32_t stored_chksum;  /* Stored metadata checksum value */
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    p = &image[0];
+
+    HDlseek(md_fd, (HDoff_t)0, SEEK_SET);
+    HDread(md_fd, image, H5FD_MD_HEADER_SIZE);
+
+    /* Magic number */
+    if(HDmemcmp(p, H5FD_MD_HEADER_MAGIC, (size_t)H5_SIZEOF_MAGIC))
+        HGOTO_ERROR(H5E_VFL, H5E_CANTLOAD, NULL, "wrong metadata file header signature")
+    p += H5_SIZEOF_MAGIC;
+
+    UINT32DECODE(p, fs_page_size);
+    UINT64DECODE(p, tick_num);
+    UINT64DECODE(p, index_offset);
+    UINT64DECODE(p, index_length);
+
+    /* NEED to verify checksum/retry ?? */
+    /* Metadata checksum */
+    UINT32DECODE(p, stored_chksum);
+
+    /* Sanity check */
+    HDassert((size_t)(p - (const uint8_t *)&image[0]) <= len);
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+}  /* H5FD_vfd_swmr_hdr_deserialize() */
+#endif
diff --git a/src/H5FDprivate.h b/src/H5FDprivate.h
index 0430064..1698d96 100644
--- a/src/H5FDprivate.h
+++ b/src/H5FDprivate.h
@@ -38,6 +38,45 @@
 /* Length of filename buffer */
 #define H5FD_MAX_FILENAME_LEN      1024
 
+/* 
+ * VFD SWMR 
+ */
+/* Metadata file header */
+#define H5FD_MD_HEADER_MAGIC            "VHDR"          /* Header magic */
+#define H5FD_SIZEOF_CHKSUM              4               /* Size of checksum */
+
+/* Size of the header in the metadata file */
+#define H5FD_MD_HEADER_SIZE                                                 \
+    (                                                                       \
+    H5_SIZEOF_MAGIC                 /* Signature */                         \
+    + 4                             /* Page size */                         \
+    + 8                             /* Tick number */                       \
+    + 8                             /* Index offset */                      \
+    + 8                             /* Index length number */               \
+    + H5FD_SIZEOF_CHKSUM            /* Metadata header checksum */          \
+    )
+
+/* Size of an index entry in the metadata file */
+#define H5FD_MD_INDEX_ENTRY_SIZE                                            \
+    (                                                                       \
+    4                               /* HDF5 file page offset */             \
+    + 4                             /* Metadata file page offset */         \
+    + 4                             /* Length */                            \
+    )
+
+/* Metadata file index magic */
+#define H5FD_MD_INDEX_MAGIC            "VIDX"          /* Index magic */
+
+/* Size of the metadata file index */
+#define H5FD_MD_INDEX_SIZE(N)           /* N is number of entries in index */   \
+    (                                                                           \
+    H5_SIZEOF_MAGIC                     /* Signature */                         \   
+    + 8                                 /* Tick num */                          \
+    + 4                                 /* Number of entries */                 \
+    + (N * H5FD_MD_INDEX_ENTRY_SIZE)    /* Index entries */                     \
+    + H5FD_SIZEOF_CHKSUM                /* Metadata header checksum */          \
+    )
+
 #ifdef H5_HAVE_PARALLEL
 /* ======== Temporary data transfer properties ======== */
 /* Definitions for memory MPI type property */
@@ -157,6 +196,10 @@ H5_DLL herr_t H5FD_set_base_addr(H5FD_t *file, haddr_t base_addr);
 H5_DLL haddr_t H5FD_get_base_addr(const H5FD_t *file);
 H5_DLL herr_t H5FD_set_paged_aggr(H5FD_t *file, hbool_t paged);
 
+/* Function prototypes for VFD SWMR */
+H5_DLL herr_t H5FD_writer_end_of_tick();
+H5_DLL herr_t H5FD_reader_end_of_tick();
+
 /* Function prototypes for MPI based VFDs*/
 #ifdef H5_HAVE_PARALLEL
 /* General routines */
diff --git a/src/H5Fint.c b/src/H5Fint.c
index abc638a..6448027 100644
--- a/src/H5Fint.c
+++ b/src/H5Fint.c
@@ -79,6 +79,9 @@ static char *H5F__getenv_prefix_name(char **env_prefix/*in,out*/);
 static herr_t H5F_build_actual_name(const H5F_t *f, const H5P_genplist_t *fapl, const char *name, char ** /*out*/ actual_name);
 static herr_t H5F__flush_phase1(H5F_t *f);
 static herr_t H5F__flush_phase2(H5F_t *f, hbool_t closing);
+static herr_t H5F__init_vfd_swmr(H5F_t *f, hbool_t file_create);
+static herr_t H5F__init_vfd_swmr_info(H5F_t *f);
+static herr_t H5F__init_vfd_swmr_md(H5F_t *f, hbool_t file_create);
 
 
 /*********************/
@@ -184,6 +187,10 @@ H5F_get_access_plist(H5F_t *f, hbool_t app_ref)
         if(H5P_set(new_plist, H5F_ACS_PAGE_BUFFER_MIN_RAW_PERC_NAME, &(f->shared->page_buf->min_raw_perc)) < 0)
             HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't set minimum raw data fraction of page buffer")
     } /* end if */
+
+    if(H5P_set(new_plist, H5F_ACS_VFD_SWMR_CONFIG_NAME, &(f->shared->vfd_swmr_config)) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set initial metadata cache resize config.")
+
 #ifdef H5_HAVE_PARALLEL
     if(H5P_set(new_plist, H5_COLL_MD_READ_FLAG_NAME, &(f->coll_md_read)) < 0)
         HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't set collective metadata read flag")
@@ -1033,6 +1040,10 @@ H5F__new(H5F_file_t *shared, unsigned flags, hid_t fcpl_id, hid_t fapl_id, H5FD_
         if(H5P_get(plist, H5F_ACS_OBJECT_FLUSH_CB_NAME, &(f->shared->object_flush)) < 0)
             HGOTO_ERROR(H5E_FILE, H5E_CANTGET, NULL, "can't get object flush cb info")
 
+        /* Get VFD SWMR configuration */
+        if(H5P_get(plist, H5F_ACS_VFD_SWMR_CONFIG_NAME, &(f->shared->vfd_swmr_config)) < 0)
+            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, NULL, "can't get VFD SWMR config info")
+
         /* Create a metadata cache with the specified number of elements.
          * The cache might be created with a different number of elements and
          * the access property list should be updated to reflect that.
@@ -1497,7 +1508,8 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
     hbool_t             use_file_locking;   /*read from env var             */
     hbool_t             ci_load = FALSE;    /* whether MDC ci load requested */
     hbool_t             ci_write = FALSE;   /* whether MDC CI write requested */
-    H5F_t              *ret_value = NULL;   /*actual return value           */
+    hbool_t             file_create = FALSE;    /* creating a new file or not */
+    H5F_t              *ret_value = NULL;       /*actual return value           */
 
     FUNC_ENTER_NOAPI(NULL)
 
@@ -1667,6 +1679,7 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
             HGOTO_ERROR(H5E_FILE, H5E_CANTGET, NULL, "can't get minimum raw data fraction of page buffer")
     } /* end if */
 
+
     /*
      * Read or write the file superblock, depending on whether the file is
      * empty or not.
@@ -1693,6 +1706,9 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
          */
         if(H5G_mkroot(file, TRUE) < 0)
             HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, NULL, "unable to create/open root group")
+
+        file_create = TRUE;
+
     } /* end if */
     else if (1 == shared->nrefs) {
         /* Read the superblock if it hasn't been read before. */
@@ -1707,8 +1723,19 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
         /* Open the root group */
         if(H5G_mkroot(file, FALSE) < 0)
             HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, NULL, "unable to read root group")
+
     } /* end if */
 
+    if(H5F_VFD_SWMR_CONFIG(file)) {
+        /* Page buffering and page allocation strategy have to be enabled */
+        if(!page_buf_size || !H5F_PAGED_AGGR(file))
+            HGOTO_ERROR(H5E_FILE, H5E_CANTGET, NULL, "file open fail with VFD SWMR writer")
+        if(1 == shared->nrefs && H5F_INTENT(file) & H5F_ACC_RDWR) {
+            if(H5F__init_vfd_swmr(file, file_create) < 0)
+                HGOTO_ERROR(H5E_FILE, H5E_CANTSET, NULL, "file open fail with initialization for VFD SWMR writer")
+        }
+    }
+
     /*
      * Decide the file close degree.  If it's the first time to open the
      * file, set the degree to access property list value; if it's the
@@ -1812,9 +1839,15 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
     ret_value = file;
 
 done:
-    if((NULL == ret_value) && file)
+    if((NULL == ret_value) && file) {
+        if(file->shared->root_grp && file->shared->nrefs == 1) {
+            if(H5AC_expunge_tag_type_metadata(file, H5G_oloc(file->shared->root_grp)->addr, H5AC_OHDR_ID, H5AC__NO_FLAGS_SET, FALSE) < 0)
+                HDONE_ERROR(H5E_FILE, H5E_CANTEXPUNGE, NULL, "unable to expunge root group tagged entries")
+        }
+
         if(H5F__dest(file, FALSE) < 0)
             HDONE_ERROR(H5E_FILE, H5E_CANTCLOSEFILE, NULL, "problems closing file")
+    }
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5F_open() */
@@ -3685,3 +3718,173 @@ done:
     FUNC_LEAVE_NOAPI_VOL(ret_value)
 } /* H5F__format_convert() */
 
+
+/*-------------------------------------------------------------------------
+ * Function:    H5F__init_vfd_swmr
+ *
+ * Purpose:     Intitialize info and the metadata file for VFD SWMR writer.
+ *
+ * Return:      Success:        SUCCEED
+ *              Failure:        FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5F__init_vfd_swmr(H5F_t *f, hbool_t file_create)
+{
+    herr_t ret_value = SUCCEED;     /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Initialize info */
+    if(H5F__init_vfd_swmr_info(f) < 0)
+        HGOTO_ERROR(H5E_FILE, H5E_CANTSET, FAIL, "error in initializing info for VFD SWMR writer")
+
+    /* Initialize the metadata file */
+    if(H5F__init_vfd_swmr_md(f, file_create) < 0)
+       HGOTO_ERROR(H5E_FILE, H5E_CANTSET, FAIL, "error in creating metadata file for VFD SWMR writer")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5F__init_vfd_swmr() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5F__init_vfd_swmr_info
+ *
+ * Purpose:     Initialize globals and the corresponding fields in f 
+ *              for VFD SWMR writer:
+ *              --set vfd_swmr_g to TRUE
+ *              --set vfd_swmr_writer_g to TRUE
+ *              --set tick_num_g to 0
+ *              --set end_of_tick_g to the current time + tick length
+ *              --set vfd_swmr_file_g to f->shared
+ *
+ * Return:      Success:        SUCCEED
+ *              Failure:        FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5F__init_vfd_swmr_info(H5F_t *f)
+{
+    struct timespec tmp_end_of_tick;
+    herr_t ret_value = SUCCEED;     /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    HDassert(f->shared->vfd_swmr_config.vfd_swmr_writer);
+
+    vfd_swmr_g = f->shared->vfd_swmr = TRUE;
+    vfd_swmr_writer_g = f->shared->vfd_swmr_writer = TRUE;
+    tick_num_g = f->shared->tick_num = 0;
+
+    /* Get current time */
+    if(HDclock_gettime(CLOCK_MONOTONIC, &tmp_end_of_tick) < 0)
+        HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL, "can't get time via clock_gettime")
+
+    /* Increment by tick length */
+    tmp_end_of_tick.tv_nsec += f->shared->vfd_swmr_config.tick_len * 100000000;
+    tmp_end_of_tick.tv_sec += tmp_end_of_tick.tv_nsec / 1000000000;
+    tmp_end_of_tick.tv_nsec = tmp_end_of_tick.tv_nsec % 1000000000;
+    HDmemcpy(&end_of_tick_g, &tmp_end_of_tick, sizeof(struct timespec));
+    HDmemcpy(&f->shared->end_of_tick, &tmp_end_of_tick, sizeof(struct timespec));
+
+    vfd_swmr_file_g = f->shared;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5F__init_vfd_swmr_info() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5F__init_vfd_swmr_md
+ *
+ * Purpose:     Open the metadata file for VFD SMWR and allocate md_pages_reserved
+ *              in the file.  
+ *              If not creating a new file, write header and an empty index
+ *              to the file.
+ *
+ * Return:      Success:        SUCCEED
+ *              Failure:        FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5F__init_vfd_swmr_md(H5F_t *f, hbool_t file_create)
+{
+    uint8_t     image[H5FD_MD_HEADER_SIZE];                 /* Buffer for element data */
+    uint8_t     image_empty_idx[H5FD_MD_INDEX_SIZE(0)];  /* Buffer for element data */
+    uint8_t     *p = NULL;              /* Pointer to buffer */
+    uint32_t    metadata_chksum;        /* Computed metadata checksum value */
+    int         fd;                     /* File descriptor */
+    herr_t      ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Open the metadata file */
+    if((fd = HDopen(f->shared->vfd_swmr_config.md_file_path, O_CREAT|O_RDWR, H5_POSIX_CREATE_MODE_RW)) < 0)
+        HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL, "unable to open metadata file")
+
+    /* Set the file to md_pages_reserved */
+    if(HDftruncate(fd, (HDoff_t)f->shared->vfd_swmr_config.md_pages_reserved * f->shared->fs_page_size) < 0)
+        HGOTO_ERROR(H5E_FILE, H5E_SEEKERROR, FAIL, "unable to extend file properly")
+
+    if(!file_create) {
+        /*
+         * Encode metadata file header
+         */
+        p = &image[0];
+
+        /* Magic for header */
+        HDmemcpy(p, H5FD_MD_HEADER_MAGIC, (size_t)H5_SIZEOF_MAGIC);
+        p += H5_SIZEOF_MAGIC;
+
+        UINT32ENCODE(p, f->shared->fs_page_size);
+        UINT64ENCODE(p, f->shared->tick_num);
+        UINT64ENCODE(p, H5FD_MD_HEADER_SIZE);
+        UINT64ENCODE(p, H5FD_MD_INDEX_SIZE(0));
+
+        metadata_chksum = H5_checksum_metadata((uint8_t *)p, (size_t)(p - &image[0]), 0);
+
+        /* Checksum for header */
+        UINT32ENCODE(p, metadata_chksum);
+
+        /* Sanity checks */
+        HDassert((size_t)(p - &image[0] == H5FD_MD_HEADER_SIZE));
+
+        /* Write header to the metadata file */
+        if(HDwrite(fd, &image[0], H5FD_MD_HEADER_SIZE) != H5FD_MD_HEADER_SIZE)
+            HGOTO_ERROR(H5E_FILE, H5E_WRITEERROR, FAIL, "error in writing header to metadata file")
+
+        /*
+         * Encode metadata file index
+         */
+        p = &image_empty_idx[0];
+
+        /* Magic for index */
+        HDmemcpy(p, H5FD_MD_INDEX_MAGIC, (size_t)H5_SIZEOF_MAGIC);
+        p += H5_SIZEOF_MAGIC;
+
+        UINT64ENCODE(p, f->shared->tick_num);
+
+        /* No entry in index */
+        UINT32ENCODE(p, 0);
+
+        metadata_chksum = H5_checksum_metadata((uint8_t *)p, (size_t)(p - &image_empty_idx[0]), 0);
+
+        /* Checksum for index */
+        UINT32ENCODE(p, metadata_chksum);
+
+        /* sanity checks */
+        HDassert((size_t)(p - &image_empty_idx[0] ==  H5FD_MD_INDEX_SIZE(0)));
+
+        /* Write index to the metadata file */
+        if(HDwrite(fd, &image_empty_idx[0],  H5FD_MD_INDEX_SIZE(0)) !=  H5FD_MD_INDEX_SIZE(0))
+             HGOTO_ERROR(H5E_FILE, H5E_WRITEERROR, FAIL, "error in writing index to metadata file")
+    }
+    f->shared->vfd_swmr_md_fd = fd;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5F__init_vfd_swmr_md() */
diff --git a/src/H5Fpkg.h b/src/H5Fpkg.h
index 2ab41de..19c49fb 100644
--- a/src/H5Fpkg.h
+++ b/src/H5Fpkg.h
@@ -353,6 +353,15 @@ struct H5F_file_t {
 
     /* Object flush info */
     H5F_object_flush_t 	object_flush;	    /* Information for object flush callback */
+
+    /* VFD SWMR configuration info */
+    H5F_vfd_swmr_config_t vfd_swmr_config;  /* Copy of the VFD SWMR configuration from the
+                                               FAPL used to open the file */
+    hbool_t vfd_swmr;                       /* The file is opened with VFD SWMR configured or not*/
+    hbool_t vfd_swmr_writer;                /* This is the VFD SWMR writer or not */
+    uint64_t tick_num;                      /* Number of the current tick */
+    struct timespec end_of_tick;            /* End time of the current tick */
+    int vfd_swmr_md_fd;                     /* POSIX: file descriptor of the metadata file */
 };
 
 /*
diff --git a/src/H5Fprivate.h b/src/H5Fprivate.h
index 979ba7d..9c7ea9e 100644
--- a/src/H5Fprivate.h
+++ b/src/H5Fprivate.h
@@ -331,6 +331,7 @@ typedef struct H5F_t H5F_t;
 #define H5F_POINT_OF_NO_RETURN(F) ((F)->shared->fs.point_of_no_return)
 #define H5F_FIRST_ALLOC_DEALLOC(F) ((F)->shared->first_alloc_dealloc)
 #define H5F_EOA_PRE_FSM_FSALLOC(F) ((F)->shared->eoa_pre_fsm_fsalloc)
+#define H5F_USE_VFD_SWMR(F)  ((F)->shared->vfd_swmr)
 #else /* H5F_MODULE */
 #define H5F_LOW_BOUND(F)        (H5F_get_low_bound(F))
 #define H5F_HIGH_BOUND(F)       (H5F_get_high_bound(F))
@@ -388,6 +389,7 @@ typedef struct H5F_t H5F_t;
 #define H5F_POINT_OF_NO_RETURN(F) (H5F_get_point_of_no_return(F))
 #define H5F_FIRST_ALLOC_DEALLOC(F) (H5F_get_first_alloc_dealloc(F))
 #define H5F_EOA_PRE_FSM_FSALLOC(F) (H5F_get_eoa_pre_fsm_fsalloc(F))
+#define H5F_USE_VFD_SWMR(F)     (H5F_use_vfd_swmr(F))
 #endif /* H5F_MODULE */
 
 
@@ -508,6 +510,20 @@ typedef struct H5F_t H5F_t;
 #define H5F_ACS_PAGE_BUFFER_MIN_META_PERC_NAME  "page_buffer_min_meta_perc" /* the min metadata percentage for the page buffer cache */
 #define H5F_ACS_PAGE_BUFFER_MIN_RAW_PERC_NAME   "page_buffer_min_raw_perc" /* the min raw data percentage for the page buffer cache */
 
+/* Default configuration for VFD SWMR: not configured */
+#define H5F_ACS_VFD_SWMR_CONFIG_NAME    "vfd_swmr_config" /* VFD SWMR configuration */
+#define H5F__DEFAULT_VFD_SWMR_CONFIG                                                \
+{                                                                                   \
+  /* int32_t    version                 = */ 0,                                     \
+  /* int32_t    tick_len                = */ 0,                                     \
+  /* int32_t    max_lag                 = */ 0,                                     \
+  /* hbool_t    vfd_swmr_writer         = */ FALSE,                                 \
+  /* hbool_t    flush_raw_data          = */ FALSE,                                 \
+  /* int32_t    md_pages_reserved       = */ 0,                                     \
+  /* char       md_file_path[]          = */ "",                                    \
+  /* char       log_file_path[]         = */ ""                                     \
+}
+
 /* ======================== File Mount properties ====================*/
 #define H5F_MNT_SYM_LOCAL_NAME         "local"                 /* Whether absolute symlinks local to file. */
 
@@ -575,6 +591,9 @@ typedef struct H5F_t H5F_t;
 /* Check for file using paged aggregation */
 #define H5F_PAGED_AGGR(F) (F->shared->fs_strategy == H5F_FSPACE_STRATEGY_PAGE && F->shared->fs_page_size)
 
+/* Check for file configured with VFD SWMR */
+#define H5F_VFD_SWMR_CONFIG(F)  (F->shared->vfd_swmr_config.version >= H5F__CURR_VFD_SWMR_CONFIG_VERSION)
+
 /* Metadata read attempt values */
 #define H5F_METADATA_READ_ATTEMPTS        1    /* Default # of read attempts for non-SWMR access */
 #define H5F_SWMR_METADATA_READ_ATTEMPTS        100    /* Default # of read attempts for SWMR access */
@@ -651,6 +670,8 @@ struct H5P_genplist_t;
 /* Main file structures */
 typedef struct H5F_file_t H5F_file_t;
 
+extern H5F_file_t *vfd_swmr_file_g;
+
 /* Block aggregation structure */
 typedef struct H5F_blk_aggr_t H5F_blk_aggr_t;
 
@@ -741,6 +762,7 @@ H5_DLL hsize_t H5F_get_pgend_meta_thres(const H5F_t *f);
 H5_DLL hbool_t H5F_get_point_of_no_return(const H5F_t *f);
 H5_DLL hbool_t H5F_get_first_alloc_dealloc(const H5F_t *f);
 H5_DLL haddr_t H5F_get_eoa_pre_fsm_fsalloc(const H5F_t *f);
+H5_DLL hbool_t H5F_use_vfd_swmr(const H5F_t *f);
 
 /* Functions than retrieve values set/cached from the superblock/FCPL */
 H5_DLL haddr_t H5F_get_base_addr(const H5F_t *f);
diff --git a/src/H5Fpublic.h b/src/H5Fpublic.h
index 73c59f5..a685d25 100644
--- a/src/H5Fpublic.h
+++ b/src/H5Fpublic.h
@@ -217,6 +217,19 @@ typedef struct H5F_retry_info_t {
 /* Callback for H5Pset_object_flush_cb() in a file access property list */
 typedef herr_t (*H5F_flush_cb_t)(hid_t object_id, void *udata);
 
+/* VFD SWMR configuration data used by H5Pset/get_vfd_swmr_config */
+#define H5F__CURR_VFD_SWMR_CONFIG_VERSION 1
+#define H5F__MAX_VFD_SWMR_FILE_NAME_LEN   1024
+typedef struct H5F_vfd_swmr_config_t {
+    int32_t     version;
+    int32_t     tick_len;
+    int32_t     max_lag;
+    hbool_t     vfd_swmr_writer;
+    hbool_t     flush_raw_data;
+    int32_t     md_pages_reserved;
+    char        md_file_path[H5F__MAX_VFD_SWMR_FILE_NAME_LEN + 1];
+    char        log_file_path[H5F__MAX_VFD_SWMR_FILE_NAME_LEN + 1];
+} H5F_vfd_swmr_config_t;
 
 #ifdef __cplusplus
 extern "C" {
@@ -274,6 +287,9 @@ H5_DLL herr_t H5Fget_page_buffering_stats(hid_t file_id, unsigned accesses[2],
     unsigned hits[2], unsigned misses[2], unsigned evictions[2], unsigned bypasses[2]);
 H5_DLL herr_t H5Fget_mdc_image_info(hid_t file_id, haddr_t *image_addr, hsize_t *image_size);
 
+/* VFD SWMR */
+H5_DLL herr_t H5Fvfd_swmr_end_tick(hid_t file_id);
+
 #ifdef H5_HAVE_PARALLEL
 H5_DLL herr_t H5Fset_mpi_atomicity(hid_t file_id, hbool_t flag);
 H5_DLL herr_t H5Fget_mpi_atomicity(hid_t file_id, hbool_t *flag);
diff --git a/src/H5Fquery.c b/src/H5Fquery.c
index be24072..41d885a 100644
--- a/src/H5Fquery.c
+++ b/src/H5Fquery.c
@@ -1215,3 +1215,26 @@ H5F_get_eoa_pre_fsm_fsalloc(const H5F_t *f)
     FUNC_LEAVE_NOAPI(f->shared->eoa_pre_fsm_fsalloc)
 } /* end H5F_get_eoa_pre_fsm_fsalloc() */
 
+
+/*-------------------------------------------------------------------------
+ * Function: H5F_use_vfd_swmr
+ *
+ * Purpose:  Quick and dirty routine to determine if VFD SWMR is
+ *           enabled for this file.
+ *           (Mainly added to stop non-file routines from poking about in the
+ *           H5F_t data structure)
+ *
+ * Return:   TRUE/FALSE on success/abort on failure (shouldn't fail)
+ *-------------------------------------------------------------------------
+ */
+hbool_t
+H5F_use_vfd_swmr(const H5F_t *f)
+{
+    /* Use FUNC_ENTER_NOAPI_NOINIT_NOERR here to avoid performance issues */
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    HDassert(f);
+    HDassert(f->shared);
+
+    FUNC_LEAVE_NOAPI(f->shared->vfd_swmr)
+} /* end H5F_use_vfd_swmr() */
diff --git a/src/H5Pfapl.c b/src/H5Pfapl.c
index 7ba9c11..a0291e6 100644
--- a/src/H5Pfapl.c
+++ b/src/H5Pfapl.c
@@ -259,6 +259,11 @@
 #define H5F_ACS_PAGE_BUFFER_MIN_RAW_PERC_ENC            H5P__encode_unsigned
 #define H5F_ACS_PAGE_BUFFER_MIN_RAW_PERC_DEC            H5P__decode_unsigned
 
+/* Definitions for the VFD SWMR configuration */
+#define H5F_ACS_VFD_SWMR_CONFIG_SIZE   sizeof(H5F_vfd_swmr_config_t)
+#define H5F_ACS_VFD_SWMR_CONFIG_DEF    H5F__DEFAULT_VFD_SWMR_CONFIG
+#define H5F_ACS_VFD_SWMR_CONFIG_ENC    H5P__facc_vfd_swmr_config_enc
+#define H5F_ACS_VFD_SWMR_CONFIG_DEC    H5P__facc_vfd_swmr_config_dec
 
 /******************/
 /* Local Typedefs */
@@ -306,6 +311,8 @@ static herr_t H5P__facc_multi_type_enc(const void *value, void **_pp, size_t *si
 static herr_t H5P__facc_multi_type_dec(const void **_pp, void *value);
 static herr_t H5P__facc_libver_type_enc(const void *value, void **_pp, size_t *size);
 static herr_t H5P__facc_libver_type_dec(const void **_pp, void *value);
+static herr_t H5P__facc_vfd_swmr_config_enc(const void *value, void **_pp, size_t *size);
+static herr_t H5P__facc_vfd_swmr_config_dec(const void **_pp, void *value);
 
 /* Metadata cache log location property callbacks */
 static herr_t H5P_facc_mdc_log_location_enc(const void *value, void **_pp, size_t *size);
@@ -398,6 +405,8 @@ static const size_t H5F_def_page_buf_size_g = H5F_ACS_PAGE_BUFFER_SIZE_DEF;
 static const unsigned H5F_def_page_buf_min_meta_perc_g = H5F_ACS_PAGE_BUFFER_MIN_META_PERC_DEF;      /* Default page buffer minimum metadata size */
 static const unsigned H5F_def_page_buf_min_raw_perc_g = H5F_ACS_PAGE_BUFFER_MIN_RAW_PERC_DEF;      /* Default page buffer mininum raw data size */
 
+static const H5F_vfd_swmr_config_t *H5F_def_vfd_swmr_config_g = H5F_ACS_VFD_SWMR_CONFIG_DEF;  /* Default vfd swmr configuration */
+
 
 /*-------------------------------------------------------------------------
  * Function:    H5P__facc_reg_prop
@@ -644,6 +653,12 @@ H5P__facc_reg_prop(H5P_genclass_t *pclass)
             NULL, NULL, NULL, NULL) < 0)
         HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
 
+    /* Register the default VFD SWMR configuration */
+    if(H5P_register_real(pclass, H5F_ACS_VFD_SWMR_CONFIG_NAME, H5F_ACS_VFD_SWMR_CONFIG_SIZE, &H5F_def_vfd_swmr_config_g,
+            NULL, NULL, NULL, H5F_ACS_VFD_SWMR_CONFIG_ENC, H5F_ACS_VFD_SWMR_CONFIG_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() */
@@ -3643,6 +3658,7 @@ H5P__facc_cache_config_dec(const void **_pp, void *_value)
     enc_size = *(*pp)++;
     HDassert(enc_size < 256);
     UINT64DECODE_VAR(*pp, enc_value, enc_size);
+
     config->max_size = (size_t)enc_value;
 
     enc_size = *(*pp)++;
@@ -3927,6 +3943,105 @@ H5P__facc_libver_type_dec(const void **_pp, void *_value)
 
 
 /*-------------------------------------------------------------------------
+ * Function:    H5P__facc_vfd_swmr_config_enc
+ *
+ * Purpose:     Callback routine which is called whenever the VFD SWMR config
+ *              property in the file access property list is encoded.
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ * Programmer:  Vailin Choi; July 2018
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5P__facc_vfd_swmr_config_enc(const void *value, void **_pp, size_t *size)
+{
+    const H5F_vfd_swmr_config_t *config = (const H5F_vfd_swmr_config_t *)value; /* Create local aliases for values */
+    uint8_t **pp = (uint8_t **)_pp;
+
+    FUNC_ENTER_STATIC_NOERR
+
+    /* Sanity check */
+    HDassert(value);
+    HDcompile_assert(sizeof(size_t) <= sizeof(uint64_t));
+
+    if(NULL != *pp) {
+
+        /* int */
+        INT32ENCODE(*pp, (int32_t)config->version);
+        INT32ENCODE(*pp, (int32_t)config->tick_len);
+        INT32ENCODE(*pp, (int32_t)config->max_lag);
+        H5_ENCODE_UNSIGNED(*pp, config->vfd_swmr_writer);
+        H5_ENCODE_UNSIGNED(*pp, config->flush_raw_data);
+        INT32ENCODE(*pp, (int32_t)config->md_pages_reserved);
+        HDmemcpy(*pp, (const uint8_t *)(config->md_file_path), (size_t)(H5F__MAX_VFD_SWMR_FILE_NAME_LEN + 1));
+        *pp += H5F__MAX_VFD_SWMR_FILE_NAME_LEN + 1;
+        HDmemcpy(*pp, (const uint8_t *)(config->log_file_path), (size_t)(H5F__MAX_VFD_SWMR_FILE_NAME_LEN + 1));
+        *pp += H5F__MAX_VFD_SWMR_FILE_NAME_LEN + 1;
+
+    } /* end if */
+
+    /* Compute encoded size */
+    *size += ( (4 * sizeof(int32_t)) + sizeof(unsigned) + 
+               (2 * (H5F__MAX_VFD_SWMR_FILE_NAME_LEN + 1)) );
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5P__facc_vfd_swmr_config_enc() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5P__facc_vfd_swmr_config_dec
+ *
+ * Purpose:     Callback routine which is called whenever the VFD SWMR
+ *              config property in the file access property list is decoded.
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ * Programmer:  Vailin Choi; July 2018
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5P__facc_vfd_swmr_config_dec(const void **_pp, void *_value)
+{
+    H5F_vfd_swmr_config_t *config = (H5F_vfd_swmr_config_t *)_value;
+    const uint8_t **pp = (const uint8_t **)_pp;
+
+    FUNC_ENTER_STATIC_NOERR
+
+    /* Sanity checks */
+    HDassert(pp);
+    HDassert(*pp);
+    HDassert(config);
+    HDcompile_assert(sizeof(size_t) <= sizeof(uint64_t));
+
+    /* Set property to default value */
+    HDmemcpy(config, &H5F_def_vfd_swmr_config_g, sizeof(H5F_vfd_swmr_config_t));
+
+    /* int */
+    INT32DECODE(*pp, config->version);
+    INT32DECODE(*pp, config->tick_len);
+    INT32DECODE(*pp, config->max_lag);
+
+    H5_DECODE_UNSIGNED(*pp, config->vfd_swmr_writer);
+    H5_DECODE_UNSIGNED(*pp, config->flush_raw_data);
+
+    /* int */
+    INT32DECODE(*pp, config->md_pages_reserved);
+
+    HDstrcpy(config->md_file_path, (const char *)(*pp));
+    *pp += H5F__MAX_VFD_SWMR_FILE_NAME_LEN + 1;
+
+    HDstrcpy(config->log_file_path, (const char *)(*pp));
+    *pp += H5F__MAX_VFD_SWMR_FILE_NAME_LEN + 1;
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5P__facc_vfd_swmr_config_dec() */
+
+/*-------------------------------------------------------------------------
  * Function:    H5Pset_core_write_tracking
  *
  * Purpose:    Enables/disables core VFD write tracking and page
@@ -4939,3 +5054,101 @@ done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5Pget_page_buffer_size() */
 
+/*-------------------------------------------------------------------------
+ * Function:    H5Pset_vfd_swmr_config
+ *
+ * Purpose:     Set VFD SWMR configuration in the target FAPL.
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ * Programmer:  Vailin Choi; July 2018
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pset_vfd_swmr_config(hid_t plist_id, H5F_vfd_swmr_config_t *config_ptr)
+{
+    H5P_genplist_t *plist;      /* Property list pointer */
+    size_t name_len;
+    herr_t ret_value = SUCCEED;   /* return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "i*x", plist_id, config_ptr);
+
+    /* 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")
+
+    /* Validate the input configuration */
+
+     /* Check args */
+    if(config_ptr == NULL)
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "NULL config_ptr on entry")
+
+    /* This field must always be set to a known version */
+    if(config_ptr->version != H5F__CURR_VFD_SWMR_CONFIG_VERSION)
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "Unknown config version")
+
+    /* This field must be >= 0 */
+    if(config_ptr->tick_len < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "tick_len must be greater than 0")
+
+    /* This field must be at least 3 */
+    if(config_ptr->max_lag < 3 )
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "max_lag must be at least 3")
+
+    /* This field must be >= 1 */
+    if(config_ptr->md_pages_reserved < 1 )
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "md_pages_reserved must be at least 1")
+
+    /* Must provide the path for the metadata file */
+    name_len = HDstrlen(config_ptr->md_file_path);
+    if(name_len == 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "md_file_path is empty")
+    else if(name_len > H5F__MAX_VFD_SWMR_FILE_NAME_LEN)
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "md_file_path is too long")
+
+    /* Set the modified config */
+    if(H5P_set(plist, H5F_ACS_VFD_SWMR_CONFIG_NAME, config_ptr) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set metadata cache initial config")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* H5Pset_vfd_swmr_config() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5Pget_vfd_swmr_config
+ *
+ * Purpose:     Retrieve the VFD SWMR configuration from the target FAPL.
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ * Programmer:  Vailin Choi; July 2018
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pget_vfd_swmr_config(hid_t plist_id, H5F_vfd_swmr_config_t *config_ptr)
+{
+    H5P_genplist_t *plist;      /* Property list pointer */
+    herr_t ret_value = SUCCEED;   /* return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "i*x", plist_id, config_ptr);
+
+    /* 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")
+
+    /* Validate the config_ptr */
+    if(config_ptr == NULL)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "NULL config_ptr on entry.")
+
+    /* Get the current VFD SWMR configuration */
+    if(H5P_get(plist, H5F_ACS_VFD_SWMR_CONFIG_NAME, config_ptr) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET,FAIL, "can't get VFD SWMR config")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* H5Pget_vfd_swmr_config() */
diff --git a/src/H5Ppublic.h b/src/H5Ppublic.h
index c5596e5..3abb3fd 100644
--- a/src/H5Ppublic.h
+++ b/src/H5Ppublic.h
@@ -370,6 +370,10 @@ H5_DLL herr_t H5Pset_mdc_image_config(hid_t plist_id, H5AC_cache_image_config_t
 H5_DLL herr_t H5Pget_mdc_image_config(hid_t plist_id, H5AC_cache_image_config_t *config_ptr /*out*/);
 H5_DLL herr_t H5Pset_page_buffer_size(hid_t plist_id, size_t buf_size, unsigned min_meta_per, unsigned min_raw_per);
 H5_DLL herr_t H5Pget_page_buffer_size(hid_t plist_id, size_t *buf_size, unsigned *min_meta_per, unsigned *min_raw_per);
+/* VFD SWMR configuration */
+H5_DLL herr_t H5Pset_vfd_swmr_config(hid_t plist_id, H5F_vfd_swmr_config_t *config_ptr);
+H5_DLL herr_t H5Pget_vfd_swmr_config(hid_t plist_id, H5F_vfd_swmr_config_t *config_ptr);
+
 
 /* Dataset creation property list (DCPL) routines */
 H5_DLL herr_t H5Pset_layout(hid_t plist_id, H5D_layout_t layout);
diff --git a/src/H5private.h b/src/H5private.h
index 8974e46..6fa81a0 100644
--- a/src/H5private.h
+++ b/src/H5private.h
@@ -982,6 +982,9 @@ typedef off_t               h5_stat_size_t;
 #ifndef HDgettimeofday
     #define HDgettimeofday(S,P)  gettimeofday(S,P)
 #endif /* HDgettimeofday */
+#ifndef HDclock_gettime
+    #define HDclock_gettime(C,T)  clock_gettime(C,T)
+#endif /* HDclock_gettime */
 #ifndef HDgetuid
     #define HDgetuid()    getuid()
 #endif /* HDgetuid */
@@ -1942,6 +1945,12 @@ extern hbool_t H5_libterm_g;    /* Is the library being shutdown? */
 #define H5_INIT_GLOBAL (H5_libinit_g)
 #define H5_TERM_GLOBAL (H5_libterm_g)
 
+/* Temporary Gobals for VFD SWMR */
+extern hbool_t vfd_swmr_g;
+extern hbool_t vfd_swmr_writer_g;
+extern uint64_t tick_num_g;
+extern struct timespec end_of_tick_g;
+
 #endif /* H5_HAVE_THREADSAFE */
 
 #ifdef H5_HAVE_CODESTACK
@@ -2058,12 +2067,32 @@ H5_DLL herr_t H5CX_pop(void);
                                                                               \
     BEGIN_MPE_LOG
 
+#define VFD_SWMR_TEST_FOR_END_OF_TICK(swmr_reader_exit, err)                                            \
+    /* Initialize the library */                                                                        \
+    if(vfd_swmr_g) {                                                                                    \
+        struct timespec curr_time;                                                                      \
+        if(HDclock_gettime(CLOCK_MONOTONIC, &curr_time) < 0)                                            \
+            HGOTO_ERROR(H5E_FUNC, H5E_CANTGET, err, "can't get time via clock_gettime")                 \
+        if( (curr_time.tv_sec >= end_of_tick_g.tv_sec) &&                                               \
+            (curr_time.tv_nsec >= end_of_tick_g.tv_nsec) ) {                                            \
+            if(vfd_swmr_writer_g) {                                                                     \
+                if(H5FD_writer_end_of_tick() < 0)                                                       \
+                    HGOTO_ERROR(H5E_FUNC, H5E_CANTSET, err, "end of tick error for VFD SWMR writer")    \
+            }                                                                                           \
+            else if(!swmr_reader_exit) {                                                                \
+                if(H5FD_reader_end_of_tick() < 0)                                                       \
+                    HGOTO_ERROR(H5E_FUNC, H5E_CANTSET, err, "end of tick error for VFD SWMR reader")    \
+            }                                                                                           \
+        }                                                                                               \
+    }
+
 /* Use this macro for all "normal" API functions */
 #define FUNC_ENTER_API(err) {{                                                \
     FUNC_ENTER_API_COMMON                                                     \
     FUNC_ENTER_API_INIT(err);                                                 \
     /* Clear thread error stack entering public functions */                  \
     H5E_clear_stack(NULL);                                                    \
+    VFD_SWMR_TEST_FOR_END_OF_TICK(FALSE, err);                                \
     {
 
 /*
@@ -2298,6 +2327,7 @@ H5_DLL herr_t H5CX_pop(void);
     H5TRACE_RETURN(ret_value);
 
 #define FUNC_LEAVE_API(ret_value)                                             \
+    VFD_SWMR_TEST_FOR_END_OF_TICK(!vfd_swmr_writer_g, ret_value);               \
     FUNC_LEAVE_API_COMMON(ret_value);                                         \
     (void)H5CX_pop();                                                         \
     H5_POP_FUNC                                                               \