Document the ioengine=net pingpong= option

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 32e5d668c89e42efec4704b2db8686afc32e17c2..b349620107f2dc9935ad07b5cdfda6e0dffc2f73 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -753,6 +753,23 @@ softrandommap=bool See norandommap. If fio runs with the random block map
                will not be as complete as with random maps, this option is
                disabled by default.
 
                will not be as complete as with random maps, this option is
                disabled by default.
 

+random_generator=str   Fio supports the following engines for generating
+               IO offsets for random IO:
+
+               tausworthe      Strong 2^88 cycle random number generator
+               lfsr            Linear feedback shift register generator
+
+               Tausworthe is a strong random number generator, but it
+               requires tracking on the side if we want to ensure that
+               blocks are only read or written once. LFSR guarantees
+               that we never generate the same offset twice, and it's
+               also less computationally expensive. It's not a true
+               random generator, however, though for IO purposes it's
+               typically good enough. LFSR only works with single
+               block sizes, not with workloads that use multiple block
+               sizes. If used with such a workload, fio may read or write
+               some blocks multiple times.
+               

 nice=int       Run the job with the given nice value. See man nice(2).
 
 prio=int       Set the io priority value of this job. Linux limits us to
 nice=int       Run the job with the given nice value. See man nice(2).
 
 prio=int       Set the io priority value of this job. Linux limits us to


@@ -1382,6 +1399,15 @@ that defines them is selected.
 [net] listen   For TCP network connections, tell fio to listen for incoming
                connections rather than initiating an outgoing connection. The
                hostname must be omitted if this option is used.
 [net] listen   For TCP network connections, tell fio to listen for incoming
                connections rather than initiating an outgoing connection. The
                hostname must be omitted if this option is used.

+[net] pingpong Normal a network writer will just continue writing data, and
+               a network reader will just consume packages. If pingpong=1
+               is set, a writer will send its normal payload to the reader,
+               then wait for the reader to send the same payload back. This
+               allows fio to measure network latencies. The submission
+               and completion latencies then measure local time spent
+               sending or receiving, and the completion latency measures
+               how long it took for the other end to receive and send back.
+

 [e4defrag] donorname=str
                File will be used as a block donor(swap extents between files)
 [e4defrag] inplace=int
 [e4defrag] donorname=str
                File will be used as a block donor(swap extents between files)
 [e4defrag] inplace=int