Token-based flow control

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index c6304a7ca2ed7bf27b65df9ce844efa88f221534..da037d2b92cf18a682d13ac7210e8404a9b8e9e0 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -1231,6 +1231,25 @@ uid=int          Instead of running as the invoking user, set the user ID to
 
 gid=int                Set group ID, see uid.
 
+flow_id=int    The ID of the flow. If not specified, it defaults to being a
+               global flow. See flow.
+
+flow=int       Weight in token-based flow control. If this value is used, then
+               there is a 'flow counter' which is used to regulate the
+               proportion of activity between two or more jobs. fio attempts
+               to keep this flow counter near zero. The 'flow' parameter
+               stands for how much should be added or subtracted to the flow
+               counter on each iteration of the main I/O loop. That is, if
+               one job has flow=8 and another job has flow=-1, then there
+               will be a roughly 1:8 ratio in how much one runs vs the other.
+
+flow_watermark=int     The maximum value that the absolute value of the flow
+               counter is allowed to reach before the job must wait for a
+               lower value of the counter.
+
+flow_sleep=int The period of time, in microseconds, to wait after the flow
+               watermark has been exceeded before retrying operations
+
 In addition, there are some parameters which are only valid when a specific
 ioengine is in use. These are used identically to normal parameters, with the
 caveat that when used on the command line, they must come after the ioengine