[Ksummit-2012-discuss] [ATTEND] writeback and kernel testing

Kamezawa Hiroyuki kamezawa.hiroyu at jp.fujitsu.com
Mon Jun 18 00:20:43 UTC 2012

(2012/06/17 12:17), Fengguang Wu wrote:
> On Sun, Jun 17, 2012 at 08:03:15AM +0530, Balbir Singh wrote:
>> On Sat, Jun 16, 2012 at 6:14 PM, Fengguang Wu<fengguang.wu at intel.com>  wrote:
>>> Greetings,
>>> I'd like to attend this year's kernel summit.
>>> I may talk about the technical challenges and trade-offs on writeback and memcg
>>> and IO controllers with anyone interested, perhaps in some breakout session.
>> Do you have a reference for the tests you've mentioned. Do you have a
>> brief summary of the challenges and trade-offs?
> - memcg with dirty limits
>    The basic agreements are, we'll do per-memcg dirty limit, but set the
>    limits reasonably high and do not expose interfaces to user space.
> - write_bps IO controller, where write_bps accounts both buffered/direct IO
>    It seems that it's possible to do a write_bps max bandwidth
>    controller at the high layer. Vivek can also extend the existing
>    controller in the block layer. The two approaches may coexist nicely.
>    Re: Integrated IO controller for buffered+direct writes
>    https://lkml.org/lkml/2012/4/23/70
> - proportional IO controller with buffered write support
>    Well it's a hard problem and we've not yet reached consensus.
>    Here is the thread with lots of details:
>    [RFC] writeback and cgroup
>    https://lkml.org/lkml/2012/4/3/314
>    Basically, Tejun's approach costs some IO/CPU/interactive
>    performance and could considerably increase writeback pages which
>    will have big problems supporting dozens of cgroups. While my
>    approach is perfectly scalable, but involves balance_dirty_pages()
>    <=>  IO scheduler interactions and will be challenging to implement.
>    Currently my attitude is,
>    - I won't go straight off to implement the balance_dirty_pages()
>      based approach without general acknowledgements beforehand.
>    - The writeback pages problem must be addressed to remove my NAK,
>      otherwise I believe it will go and bite the MM/FS developers soon.

Yes, topics seems interesting to me. I think we should have cgroup+writeback
breakout session.


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