[Lxc-users] blkio.weight doesn't work

[Zhu Yanhai]

在 2011年12月14日 下午5:30，陈竞 <cj.magina at gmail.com> 写道：
> i got the problem, my script is wrong, it should drop the cache, or it will
> read data from cache,
>  the script is :
> sync
> echo 3 > /proc/sys/vm/drop_caches
> dd if=/tmp/file1 of=/dev/null
>
>
> size of file1 is 400M, and i get new test result:
> A: blkio.weight=100    cost 11.12s   speed is 37.5MB/s
> B: blkio.weight=1000    cost 6.4s   speed is 65.7MB/s
>
> so the blkio.weight has some effect, bu the result is not as good as 1:10

No, it is good.
Blkio controller doesn't reserve bandwith for any groups, so what
happened in your test is Group B finished before Group A, and after
that Group A was able to occupy all bandwith, which made it much
faster.
So if the size of input files are the same, then the expect run time is:
For Group B: Runtime A = size / 10B
For Group A: Runtiem B = size / 10B + 0.9 * size / 11B
Then Runtime A / Runtime B = 0.55

In your test, 6.4 / 11.12 = 0.5755, so it works well.

--
Thanks,
Zhu Yanhai


>
>
> 2011/12/14 Zhu Yanhai <zhu.yanhai at gmail.com>
>>
>> And neither slice_idle nor group_idle is zero? Did you change any
>> default parameters for CFQ?
>>
>> -zyh
>>
>> 在 2011年12月14日 下午4:55，陈竞 <cj.magina at gmail.com> 写道：
>> > my io scheduler is CFQ.... So the result is weird
>> >
>> > 在 2011年12月14日 下午4:12，陈竞 <cj.magina at gmail.com>写道：
>> >
>> >> Hi， i'm using lxc in my project, i want to control disk io speed, so i
>> >> use
>> >> blkio.weight. I test it, but the result is confusing.
>> >> I create two container A and B:
>> >> A: blkio.weight = 100            B : blkio.weight=1000
>> >>
>> >> the running process in A and B are the same, which is bash script :
>> >> dd if=/tmp/xxx of=/dev/null
>> >> the size of xxx is 400Mb
>> >>
>> >> I suppose that A would be slower than B, since its weight is small,
>> >> while
>> >> the test turns out that B run as fast as A, they are in same speed.
>> >> Can any help me figure it out ?
>> >> PS: my kernel is 2.6.32, and lxc is 0.7.5
>> >> --
>> >> 陈竞，中科院计算技术研究所，高性能计算机中心
>> >> Jing Chen HPCC.ICT.AC China
>> >
>> >
>> >
>> >
>> > --
>> > 陈竞，中科院计算技术研究所，高性能计算机中心
>> > Jing Chen HPCC.ICT.AC China
>> >
>> >
>> > ------------------------------------------------------------------------------
>> > Cloud Computing - Latest Buzzword or a Glimpse of the Future?
>> > This paper surveys cloud computing today: What are the benefits?
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>
>
>
>
> --
> 陈竞，中科院计算技术研究所，高性能计算机中心
> Jing Chen HPCC.ICT.AC China