Adding userspace_libaio_reap option

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index b47d7335e30cb68f90ea2881803503755770d290..ad4e45402172f04a4563b2974c5e997462b4d30d 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -244,6 +244,7 @@ irange      Integer range with suffix. Allows value range to be given, such
        1k:4k. If the option allows two sets of ranges, they can be
        specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see
        int.
+float_list     A list of floating numbers, separated by a ':' character.
 
 With the above in mind, here follows the complete list of fio job
 parameters.
@@ -318,8 +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
@@ -569,9 +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
@@ -1120,6 +1125,18 @@ disable_slat=bool Disable measurements of submission latency numbers. See
 disable_bw=bool        Disable measurements of throughput/bandwidth numbers. See
                disable_lat.
 
+clat_percentiles=bool Enable the reporting of percentiles of
+                completion latencies.
+
+percentile_list=float_list Overwrite the default list of percentiles
+               for completion latencies. Each number is a floating
+               number in the range (0,100], and the maximum length of
+               the list is 20. Use ':' to separate the numbers, and
+               list the numbers in ascending order. For example,
+               --percentile_list=99.5:99.9 will cause fio to report
+               the values of completion latency below which 99.5% and
+               99.9% of the observed latencies fell, respectively.
+
 gtod_reduce=bool Enable all of the gettimeofday() reducing options
                (disable_clat, disable_slat, disable_bw) plus reduce
                precision of the timeout somewhat to really shrink
@@ -1170,6 +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
 ---------------------------