Hi ,
Iam running the below fio test case and collecting the cat
/sys/class/block/sda/stat before after the test.
And below are the max_sectors_kb and max_hw_sectors_kb settings for the
device.
cat /sys/class/block/sdb/queue/max_hw_sectors_kb
32767
[root@localhost ~]# cat /sys/class/block/sdb/queue/max_sectors_kb
1280
Test Case:
[root@localhost ~]#
io --filename=/dev/sdb --direct=1 --rw=write --norandommap
--randrepeat=0 --ioengine=sync
--bs=1m --iodepth=1 --numjobs=1 --group_reporting --name=4ktest --size=50m
And below is the o/p of the test .
[root@localhost ~]#cat /sys/class/block/sdb/stat
6439 0 1513128 1618 4645 0 3332736 2697
0 3356 633 0 0 0 0
[root@localhost ~]#
io --filename=/dev/sdb --direct=1 --rw=write --norandommap
--randrepeat=0 --ioengine=sync
--bs=1m --iodepth=1 --numjobs=1 --group_reporting --name=4ktest --size=50m
4ktest: (g=0): rw=write, bs=(R) 1024KiB-1024KiB, (W) 1024KiB-1024KiB, (T)
1024KiB-1024KiB, ioengine=sync, iodepth=1
fio-3.1
…..
Run status group 0 (all jobs):
WRITE: bw=943MiB/s (989MB/s), 943MiB/s-943MiB/s (989MB/s-989MB/s),
io=50.0MiB (52.4MB), run=53-53msec
Disk stats (read/write):
sdb: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%
[root@localhost ~]# cat /sys/class/block/sdb/stat
6519 0 1517272 1628 4795 0 3435136 2785
0 3420 633 0 0 0 0
And when I compare the difference between the number of write I/Os processed
between the two stats(4795-4645) it gave me 50 as it has submitted the 50
requests of 1MB each(since max_sectors_kb is set to 1280).
But when I ran the same test multiple the number of write I/Os processed
(collected as above) keeps changing which is more than 50.
Not sure on what basis the requests are getting splitted when I run same
test case on the same setup.
Any input here will help me to understand more.
Iam running kernel of 5.0.0-rc+ version.
Regards,
Muneendra
