I did a similar test to yours. I increased the number of I/Os
which are issued simultaneously up to 100 per cgroup.
Procedures:
o Prepare 300 files which size is 250MB on 1 partition sdb3
o Create three groups with priority 0, 4 and 7.
o Run many processes issuing random direct I/O with 4KB data on each
files in three groups.
#1 Run 25 processes issuing read I/O only per group.
#2 Run 100 processes issuing read I/O only per group.
o Count up the number of I/Os which have done in 10 minutes.
The number of I/Os (percentage to total I/O)
--------------------------------------------------------------
| group | group 1 | group 2 | group 3 | total |
| priority | 0(highest) | 4 | 7(lowest) | I/Os |
|-------------+------------+------------+------------+---------|
| Estimate | | | | |
| Performance | 61.5% | 30.8% | 7.7% | |
|-------------+------------+------------+------------|---------|
| #1 25procs | 52763(57%) | 30811(33%) | 9575(10%) | 93149 |
| #2 100procs | 24949(40%) | 21325(34%) | 16508(26%) | 62782 |
--------------------------------------------------------------
The result of test #1 is close to your estimation, but the result
of test #2 is not, the gap between the estimation and the result
increased.
In addition, I got the following message during test #2. Program
"ioload", our benchmark program, was blocked more than 120 seconds.
Do you see any problems?
INFO: task ioload:8456 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
ioload D 00000008 2772 8456 8419
f72eb740 00200082 c34862c0 00000008 c3565170 c35653c0 c2009d80
00000001
c1d1bea0 00200046 ffffffff f6ee039c 00000000 00000000 00000000
c2009d80
018db000 00000000 f71a6a00 c0604fb6 00000000 f71a6bc8 c04876a4
00000000
Call Trace:
[<c0604fb6>] io_schedule+0x4a/0x81
[<c04876a4>] __blockdev_direct_IO+0xa04/0xb54
[<c04a3aa2>] ext2_direct_IO+0x35/0x3a
[<c04a4757>] ext2_get_block+0x0/0x603
[<c044ab81>] generic_file_direct_IO+0x103/0x118
[<c044abe6>] generic_file_direct_write+0x50/0x13d
[<c044b59e>] __generic_file_aio_write_nolock+0x375/0x4c3
[<c046e571>] link_path_walk+0x86/0x8f
[<c044a1e8>] find_lock_page+0x19/0x6d
[<c044b73e>] generic_file_aio_write+0x52/0xa9
[<c0466256>] do_sync_write+0xbf/0x100
[<c042ca44>] autoremove_wake_function+0x0/0x2d
[<c0413366>] update_curr+0x83/0x116
[<c0605280>] mutex_lock+0xb/0x1a
[<c04b653b>] security_file_permission+0xc/0xd
[<c0466197>] do_sync_write+0x0/0x100
[<c046695d>] vfs_write+0x83/0xf6
[<c0466ea9>] sys_write+0x3c/0x63
[<c04038de>] syscall_call+0x7/0xb
[<c0600000>] print_cpu_info+0x27/0x92
=======================
Thanks,
Ryo Tsuruta
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