Clarify spread/lambda of poisson

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 03a0060c4ede820428d491f7d10b4a8143c07ed6..a534aa865d8c4a9384ebee3d823ecaaaf0fdfb3d 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -1049,7 +1049,7 @@ rate=int  Cap the bandwidth used by this job. The number is in bytes/sec,
                will only limit writes (to 500KB/sec), the latter will only
                limit reads.
 
-ratemin=int    Tell fio to do whatever it can to maintain at least this
+rate_min=int   Tell fio to do whatever it can to maintain at least this
                bandwidth. Failing to meet this requirement, will cause
                the job to exit. The same format as rate is used for
                read vs write separation.
@@ -1064,8 +1064,14 @@ rate_iops_min=int If fio doesn't meet this rate of IO, it will cause
                the job to exit. The same format as rate is used for read vs
                write separation.
 
-rate_poisson=bool      When rate limited, try to simulate request flow under
-               Poisson process (instead of even distribution). Default: false.
+rate_process=str       This option controls how fio manages rated IO
+               submissions. The default is 'linear', 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
+               'poisson', 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.
 
 latency_target=int     If set, fio will attempt to find the max performance
                point that the given workload will run at while maintaining a
@@ -1084,7 +1090,7 @@ latency_percentile=float  The percentage of IOs that must fall within the
 max_latency=int        If set, fio will exit the job if it exceeds this maximum
                latency. It will exit with an ETIME error.
 
-ratecycle=int  Average bandwidth for 'rate' and 'ratemin' over this number
+rate_cycle=int Average bandwidth for 'rate' and 'rate_min' over this number
                of milliseconds.
 
 cpumask=int    Set the CPU affinity of this job. The parameter given is a