# mount | grep /mnt/ext4
/dev/sdc1 on /mnt/ext4 type ext4 (rw,noatime,nodiratime,discard,data=writeback,barrier=0
# fio --filename=/mnt/ext4/test --direct=1 --rw=randrw --bs=16k --size=50G --numjobs=16 --runtime=120 --group_reporting --name=test --rwmixread=90 --thread --ioengine=psync
test: (g=0): rw=randrw, bs=16K-16K/16K-16K, ioengine=psync, iodepth=1
...
test: (g=0): rw=randrw, bs=16K-16K/16K-16K, ioengine=psync, iodepth=1
fio 1.58
Starting 16 threads
test: Laying out IO file(s) (1 file(s) / 51200MB)
Jobs: 16 (f=16): [mmmmmmmmmmmmmmmm] [100.0% done] [183.2M/21594K /s] [11.5K/1318  iops] [eta 00m:00s]
test: (groupid=0, jobs=16): err= 0: pid=13623
  read : io=21306MB, bw=181805KB/s, iops=11362 , runt=120002msec
    clat (usec): min=79 , max=101773 , avg=1376.09, stdev=897.95
     lat (usec): min=80 , max=101774 , avg=1377.12, stdev=897.96
    bw (KB/s) : min= 9005, max=13184, per=6.26%, avg=11374.02, stdev=322.85
  write: io=2374.2MB, bw=20266KB/s, iops=1266 , runt=120002msec
    clat (usec): min=58 , max=30634 , avg=222.96, stdev=254.09
     lat (usec): min=58 , max=30635 , avg=224.00, stdev=254.14
    bw (KB/s) : min=  622, max= 2106, per=6.26%, avg=1268.29, stdev=209.36
  cpu          : usr=9.90%, sys=37.32%, ctx=33319154, majf=0, minf=8318
  IO depths    : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0%
     submit    : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
     complete  : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
     issued r/w/d: total=1363557/151999/0, short=0/0/0
     lat (usec): 100=0.43%, 250=7.34%, 500=1.80%, 750=0.94%, 1000=6.49%
     lat (msec): 2=78.68%, 4=1.07%, 10=3.23%, 20=0.01%, 50=0.01%
     lat (msec): 100=0.01%, 250=0.01%

Run status group 0 (all jobs):
   READ: io=21306MB, aggrb=181804KB/s, minb=186167KB/s, maxb=186167KB/s, mint=120002msec, maxt=120002msec
  WRITE: io=2374.2MB, aggrb=20266KB/s, minb=20752KB/s, maxb=20752KB/s, mint=120002msec, maxt=120002msec

Disk stats (read/write):
  sdc: ios=1361870/151871, merge=0/23, ticks=1751120/17992, in_queue=1768300, util=100.00%