Increase CPU clock calibration accuracy

[fio.git] / fio.1

diff --git a/fio.1 b/fio.1
index 2db9793fac5470f840b95db192f5ed6aad8e7334..b7abc4b6f97f639e024b470b721598084ed2447b 100644 (file)
--- a/fio.1
+++ b/fio.1
@@ -486,8 +486,8 @@ transfer as fio ioengine
 .B e4defrag
 IO engine that does regular EXT4_IOC_MOVE_EXT ioctls to simulate defragment activity
 request to DDIR_WRITE event
-.TP
 .RE
+.P
 .RE
 .TP
 .BI iodepth \fR=\fPint
@@ -617,6 +617,26 @@ fails to allocate the map, if this option is set it will continue without a
 random block map. As coverage will not be as complete as with random maps, this
 option is disabled by default.
 .TP
+.BI random_generator \fR=\fPstr
+Fio supports the following engines for generating IO offsets for random IO:
+.RS
+.TP
+.B tausworthe
+Strong 2^88 cycle random number generator
+.TP
+.B lfsr
+Linear feedback shift register generator
+.TP
+.RE
+.P
+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.
+.TP
 .BI nice \fR=\fPint
 Run job with given nice value.  See \fInice\fR\|(2).
 .TP
@@ -1142,6 +1162,15 @@ 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.
 .TP
+.BI (net, pingpong) \fR=\fPbool
+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.
+.TP
 .BI (e4defrag,donorname) \fR=\fPstr
 File will be used as a block donor (swap extents between files)
 .TP