I/O investigation

gistfile1.txt

How many write syscalls?

# perf stat -e 'syscalls:sys_enter_writev'  -p 546925
^C
 Performance counter stats for process id '546925':

                 9      syscalls:sys_enter_writev

       3.400728456 seconds time elapsed

 
 

Disk queue lenght and medium size


https://www.kernel.org/doc/Documentation/ABI/testing/procfs-diskstats
[root@vmx209 ~]# awk '/nvme1n1/{ avg=$11/$8; printf"%0.2f - %d \n", avg, $12}' /proc/diskstats
0.40 - 49
[root@vmx209 ~]# awk '/nvme1n1/{ avg=$11/$8; printf"%0.2f - %d \n", avg, $12}' /proc/diskstats
0.40 - 349
[root@vmx209 ~]# awk '/nvme1n1/{ avg=$11/$8; printf"%0.2f - %d \n", avg, $12}' /proc/diskstats
0.40 - 327
[root@vmx209 ~]# awk '/nvme1n1/{ avg=$11/$8; printf"%0.2f - %d \n", avg, $12}' /proc/diskstats
0.40 - 143
[root@vmx209 ~]# awk '/nvme1n1/{ avg=$11/$8; printf"%0.2f - %d \n", avg, $12}' /proc/diskstats
0.40 - 6
[root@vmx209 ~]# awk '/nvme1n1/{ avg=$11/$8; printf"%0.2f - %d \n", avg, $12}' /proc/diskstats
0.40 - 325
[root@vmx209 ~]# awk '/nvme1n1/{ avg=$11/$8; printf"%0.2f - %d \n", avg, $12}' /proc/diskstats
0.41 - 0

 
 

time elapsed for complete a write operation

# perf record -F 100 -e syscalls:sys_enter_writev,syscalls:sys_exit_writev  -p PID
# perf script --deltatime -i perf.data.pmux.writev  > pmux.write
# cat pmux.write | ./parser.py
Processed lines 251
mean 0.055800, 50p 0.000007, 80p 0.000132, 90p 0.278581, max 0.642663