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SubjectRe: [RFC][v2][patch 0/12][CFQ-cgroup]Yet another I/O bandwidth controlling subsystem for CGroups based on CFQ
From
Hi Uchida-san,

I realized that the benchmark results which I posted on Apr 25 had
some problems with the testing environment.

From: Ryo Tsuruta <ryov@valinux.co.jp>
Subject: Re: [RFC][v2][patch 0/12][CFQ-cgroup]Yet another I/O
bandwidth controlling subsystem for CGroups based on CFQ
Date: Fri, 25 Apr 2008 18:54:44 +0900 (JST)

Uchida-san said,

> In the test #2 and #3, did you use direct write?
> I guess you have used the non-direct write I/O (using cache).

I answered "Yes," but actually I did not use direct write I/O, because
I ran these tests on Xen-HVM. Xen-HVM backend driver doesn't use direct
I/O for actual disk operations even though guest OS uses direct I/O.

An another problem was that the CPU time was used up during the tests.

So, I retested with the new testing environment and got good results.
The number of I/Os is proportioned according to the priority levels.

Details of the tests are as follows:

Envirionment:
Linux version 2.6.25-rc2-mm1 based.
CPU0: Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz stepping 06
CPU1: Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz stepping 06
Memory: 2063568k/2088576k available (2085k kernel code, 23684k
reserved, 911k data, 240k init, 1171072k highmem)
scsi 1:0:0:0: Direct-Access ATA WDC WD2500JS-55N 10.0 PQ: 0 ANSI: 5
sd 1:0:0:0: [sdb] 488397168 512-byte hardware sectors (250059 MB)
sd 1:0:0:0: [sdb] Write Protect is off
sd 1:0:0:0: [sdb] Mode Sense: 00 3a 00 00
sd 1:0:0:0: [sdb] Write cache: disabled, read cache: enabled,
doesn't support DPO or FUA
sdb: sdb1 sdb2 sdb3 sdb4 < sdb5 sdb6 sdb7 sdb8 sdb9 sdb10 sdb11
sdb12 sdb13 sdb14 sdb15 >

Procedures:
o Prepare 3 partitions sdb5, sdb6 and sdb7.
o Run 100 processes issuing random direct I/O with 4KB data on each
partitions.
o Run 3 tests:
#1 issuing read I/O only.
#2 issuing write I/O only.
#3 sdb5 and sdb6 are read, sdb7 is write.
o Count up the number of I/Os which have done in 60 seconds.

Results:
Vasily's scheduler
The number of I/Os (percentage to total I/Os)
---------------------------------------------------------------------
| partition | sdb5 | sdb6 | sdb7 | total |
| priority | 7(highest) | 4 | 0(lowest) | I/Os |
|---------------+--------------+--------------+--------------|--------|
| #1 read | 3383(35%) | 3164(33%) | 3142(32%) | 9689 |
| #2 write | 3017(42%) | 2372(33%) | 1851(26%) | 7240 |
| #3 read&write | 4300(36%) | 3127(27%) | 1521(17%) | 8948 |
---------------------------------------------------------------------

Satoshi's scheduler
The number of I/Os (percentage to total I/O)
---------------------------------------------------------------------
| partition | sdb5 | sdb6 | sdb7 | total |
| priority | 0(highest) | 4 | 7(lowest) | I/Os |
|---------------+--------------+--------------+--------------|--------|
| #1 read | 3907(47%) | 3126(38%) | 1260(15%) | 8293 |
| #2 write | 3389(41%) | 3024(36%) | 1901(23%) | 8314 |
| #3 read&write | 5028(53%) | 3961(42%) | 441( 5%) | 9430 |
---------------------------------------------------------------------

Thanks,
Ryo Tsuruta


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