Clarify spread/lambda of poisson

[fio.git] / fio.1

diff --git a/fio.1 b/fio.1
index 2ecc3d3300f389dc37ab0193005d3e5f899abf3f..3cc353a3c02a698f709fc6bce6cdbeefec5124d7 100644 (file)
--- a/fio.1
+++ b/fio.1
@@ -948,7 +948,7 @@ limit reads to 1MB/sec and writes to 500KB/sec. Capping only reads or writes
 can be done with \fBrate\fR=,500k or \fBrate\fR=500k,. The former will only
 limit writes (to 500KB/sec), the latter will only limit reads.
 .TP
-.BI ratemin \fR=\fPint
+.BI rate_min \fR=\fPint
 Tell \fBfio\fR to do whatever it can to maintain at least the given bandwidth.
 Failing to meet this requirement will cause the job to exit. The same format
 as \fBrate\fR is used for read vs write separation.
@@ -963,12 +963,17 @@ size is used as the metric.
 If this rate of I/O is not met, the job will exit. The same format as \fBrate\fR
 is used for read vs write separation.
 .TP
-.BI poisson \fR=\fPbool
-When rate limited, try simulate request flow under Poisson process (instead
-of even distribution). Default: false.
-.TP
-.BI ratecycle \fR=\fPint
-Average bandwidth for \fBrate\fR and \fBratemin\fR over this number of
+.BI rate_process \fR=\fPstr
+This option controls how fio manages rated IO submissions. The default is
+\fBlinear\fR, which submits IO in a linear fashion with fixed delays between
+IOs that gets adjusted based on IO completion rates. If this is set to
+\fBpoisson\fR, fio will submit IO based on a more real world random request
+flow, known as the Poisson process
+(https://en.wikipedia.org/wiki/Poisson_process). The lambda will be
+10^6 / IOPS for the given workload.
+.TP
+.BI rate_cycle \fR=\fPint
+Average bandwidth for \fBrate\fR and \fBrate_min\fR over this number of
 milliseconds.  Default: 1000ms.
 .TP
 .BI latency_target \fR=\fPint