Token-based flow control
This patch allows two fio jobs to be kept to a certain
proportion of each other using token-based flow control.
There are three new parameters: flow, flow_watermark, and
flow_sleep, documented in the fio options. An example of an fio
job using these parameters is below:
[global]
norandommap
thread
time_based
runtime=30
direct=1
ioengine=libaio
iodepth=256
size=100g
bs=8k
filename=/tmp/testfile
flow_watermark=100
flow_sleep=1000
[job2]
numjobs=1
rw=write
flow=-8
[job1]
numjobs=1
rw=randread
flow=1
The motivating application of this patch was to allow random reads
and sequential writes at a particular given proportion.
This initial version is only correct when run with 'thread', as shared
state is represented with a global variable. It also only allows two
jobs to be synchronized properly. A future version might do more, but
no more functionality was needed for my application.
Tested: Ran a few fio jobs with this flow control, observing
the proportion of IOPS to match what was intended by the job file.
Varied the flow_watermark and flow_sleep parameters and observed
the effect on throughput.
Signed-off-by: Dan Ehrenberg <dehrenberg@google.com>
Modified by me to support flow_id, so an arbitrary number of flows can
be used. This means it no longer relies on global context, so it can be
used from a thread or process alike. Also added man page documentation.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/options.c b/options.c
index c3fdb56..bd8141a 100644
--- a/options.c
+++ b/options.c
@@ -2170,6 +2170,40 @@
.help = "Run job with this group ID",
},
{
+ .name = "flow_id",
+ .type = FIO_OPT_INT,
+ .off1 = td_var_offset(flow_id),
+ .help = "The flow index ID to use",
+ .def = "0",
+ },
+ {
+ .name = "flow",
+ .type = FIO_OPT_INT,
+ .off1 = td_var_offset(flow),
+ .help = "Weight for flow control of this job",
+ .parent = "flow_id",
+ .def = "0",
+ },
+ {
+ .name = "flow_watermark",
+ .type = FIO_OPT_INT,
+ .off1 = td_var_offset(flow_watermark),
+ .help = "High watermark for flow control. This option"
+ " should be set to the same value for all threads"
+ " with non-zero flow.",
+ .parent = "flow_id",
+ .def = "1024",
+ },
+ {
+ .name = "flow_sleep",
+ .type = FIO_OPT_INT,
+ .off1 = td_var_offset(flow_sleep),
+ .help = "How many microseconds to sleep after being held"
+ " back by the flow control mechanism",
+ .parent = "flow_id",
+ .def = "0",
+ },
+ {
.name = NULL,
},
};