Add documentation for 'sync_file_range'

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 886515b7aa754527070ee24ab785d66abb5b0b3e..6c7f05b9efde3334e5260b4c86371216d43de3b3 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -566,11 +566,25 @@ fsync=int If writing to a file, issue a sync of the dirty data
                not sync the file. The exception is the sg io engine, which
                synchronizes the disk cache anyway.
 
-fsyncdata=int  Like fsync= but uses fdatasync() to only sync data and not
+fdatasync=int  Like fsync= but uses fdatasync() to only sync data and not
                metadata blocks.
                In FreeBSD there is no fdatasync(), this falls back to
                using fsync()
 
+sync_file_range=str:val        Use sync_file_range() for every 'val' number of
+               write operations. Fio will track range of writes that
+               have happened since the last sync_file_range() call. 'str'
+               can currently be one or more of:
+
+               wait_before     SYNC_FILE_RANGE_WAIT_BEFORE
+               write           SYNC_FILE_RANGE_WRITE
+               wait_after      SYNC_FILE_RANGE_WAIT_AFTER
+
+               So if you do sync_file_range=wait_before,write:8, fio would
+               use SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE for
+               every 8 writes. Also see the sync_file_range(2) man page.
+               This option is Linux specific.
+
 overwrite=bool If true, writes to a file will always overwrite existing
                data. If the file doesn't already exist, it will be
                created before the write phase begins. If the file exists