Adding userspace_libaio_reap option

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 3b60f58e0e367d1e593de9337b78b0ffb47f5d24..ad4e45402172f04a4563b2974c5e997462b4d30d 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -319,8 +319,12 @@ rw=str             Type of io pattern. Accepted values are:
                a number of IO's to do before getting a new offset, this is
                one by appending a ':<nr>' to the end of the string given.
                For a random read, it would look like 'rw=randread:8' for
-               passing in an offset modifier with a value of 8. See the
-               'rw_sequencer' option.
+               passing in an offset modifier with a value of 8. If the
+               postfix is used with a sequential IO pattern, then the value
+               specified will be added to the generated offset for each IO.
+               For instance, using rw=write:4k will skip 4k for every
+               write. It turns sequential IO into sequential IO with holes.
+               See the 'rw_sequencer' option.
 
 rw_sequencer=str If an offset modifier is given by appending a number to
                the rw=<str> line, then this option controls how that
@@ -570,9 +574,9 @@ ioengine=str        Defines how the job issues io to the file. The following
                                for more info on GUASI.
 
                        rdma    The RDMA I/O engine  supports  both  RDMA
-                               memory semantic(RDMA_WRITE/RDMA_READ) and
-                               channel semantic(Send/Recv) in InfiniBand, RoCE
-                               and iWarp environment.
+                               memory semantics (RDMA_WRITE/RDMA_READ) and
+                               channel semantics (Send/Recv) for the
+                               InfiniBand, RoCE and iWARP protocols.
 
                        external Prefix to specify loading an external
                                IO engine object file. Append the engine
@@ -1183,6 +1187,13 @@ uid=int          Instead of running as the invoking user, set the user ID to
 
 gid=int                Set group ID, see uid.
 
+userspace_libaio_reap=bool  Normally, with the libaio engine in use, fio
+               will use the io_getevents system call to reap newly returned
+               events. With this flag turned on, the AIO ring will be read
+               directly from user-space to reap events. The reaping mode is
+               only enabled when polling for a minimum of 0 events (eg when
+               iodepth_batch_complete=0).
+
 6.0 Interpreting the output
 ---------------------------