bug report

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Hi,

When I am using fio to do some tests, I find a problem.

I am using a client with a 10Gb NIC to do the test case of sequential read, and the configuration file is below:

//version 2.0.8
global]
iodepth=256
runtime=600
ioengine=libaio
direct=1
size=30g
filename=/dev/vdb
ramp_time=10

[seq-read-64k]
rw=read
bs=64k
iodepth_batch_submit=8
iodepth_batch_complete=8


we know the bandwidth can reach nearly 1100MB/s without the parameter of rate. It will finish fio in about 30 seconds, because the size is 30g.

first, when I set ramp_time to 10, the fio result is below:

seq-read-64k: (groupid=0, jobs=1): err= 0: pid=26840
  read : io=20016MB, bw=1105.8MB/s, iops=17677 , runt= 18102msec

second, when I set ramp_time to 35, the fio result is below:

seq-read-64k: (groupid=0, jobs=1): err= 0: pid=26861
  read : io=30720MB, bw=1102.3MB/s, iops=17636 , runt= 27870msec

According to these, we can summary:

1. When we set ramp_time less than the time of fio finish read(we call it fftime for short), then
     Runt = fftime - ramptime
2. When we set ramp_time greater than the time of fio finish read(we call it fftime for short), then
  Runt = fftime
My requirement is:
  I want to use ramp time to warm up 50 seconds, and then collect iostat data, but fio has finished after 30 seconds, so I will collect all empty data.

Could we not calculate time and io size during ramp time in runt time, or do I have some mistakes to understand it?
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