Re: [patch 0/4] [RFC] Another proportional weight IO controller

[Li Zefan <lizf@cn.fujitsu.com>]

Vivek Goyal wrote:
> On Fri, Nov 14, 2008 at 02:44:22PM -0800, Nauman Rafique wrote:
>> In an attempt to make sure that this discussion leads to
>> something useful, we have summarized the points raised in this
>> discussion and have come up with a strategy for future.
>> The goal of this is to find common ground between all the approaches
>> proposed on this mailing list.
>>
>> 1 Start with Satoshi's latest patches.
> 
> I have had a brief look at both Satoshi's patch and bfq. I kind of like
> bfq's patches for keeping track of per cgroup, per queue data structures.
> May be we can look there also.
> 
>> 2 Do the following to support propotional division:
>>  a) Give time slices in proportion to weights (configurable
>>  option). We can support both priorities and weights by doing
>>  propotional division between requests with same priorities.
>> 3 Schedule time slices using WF2Q+ instead of round robin.
>>  Test the performance impact (both throughput and jitter in latency).
>> 4 Do the following to support the goals of 2 level schedulers:
>>  a) Limit the request descriptors allocated to each cgroup by adding
>>  functionality to elv_may_queue()
>>  b) Add support for putting an absolute limit on IO consumed by a
>>  cgroup. Such support exists in dm-ioband and is provided by Andrea
>>  Righi's patches too.
> 
> Does dm-iobnd support abosolute limit? I think till last version they did
> not. I have not check the latest version though.
> 

No, dm-ioband still provides weight/share control only. Only Andrea Righi's
patches support absolute limit.

>>  c) Add support (configurable option) to keep track of total disk
>> time/sectors/count
>>  consumed at each device, and factor that into scheduling decision
>>  (more discussion needed here)
>> 5 Support multiple layers of cgroups to align IO controller behavior
>>  with CPU scheduling behavior (more discussion?)
>> 6 Incorporate an IO tracking approach which re-uses memory resource
>> controller code but is not dependent on it (may be biocgroup patches from
>> dm-ioband can be used here directly)
>> 7 Start an offline email thread to keep track of progress on the above
>> goals.
>>
>> Please feel free to add/modify items to the list
>> when you respond back. Any comments/suggestions are more than welcome.
>>