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[Xen-devel] Re: IO controller Mini-Summit 2009

Hi Vivek,

Thank you for CCing me.

I just wanted to let you know that Ted Tso was kind enough to let
us give a readout for the mini-summit at the kernel summit.

There will be other mini-summits sharing 50 minutes so we need to
keep each mini-summit readout to 5-6 minutes of presentation and
4-5 minutes of questions/discussions.

Yoshikawa-san and myself were planning to take notes of the
mini-summit, but it would be great if you could share yours.  The
idea is to use those to prepare a brief mini-summit report (4-5
slides) that we can show at the kernel summit.

Later in the day, after the mini-summit, we would be sending a
draft version of the slides to the relevant mailing lists for you
to review. Since the mini-summit readouts will take place on
Monday I would appreciate it if you could comment on them before
Sunday night the latest.



Vivek Goyal wrote:
On Wed, Oct 14, 2009 at 09:24:44PM +0900, Ryo Tsuruta wrote:

Hi Ryo,

CCing people who are planning to attend the mini summit either in person
or phone. (As per your list on io mini summit wiki page). Not sure if
everybody is scanning mailing list for update on mini summit.

I am checking out wiki page for more information like Venue. It says the
venue is linux foundation office Japan. Hopefully there is no change in
that information.

What are the conference call details for the people who might want to join
in over phone? Could not find those. Are you yet to post these?


I have summarized the topics for the IO controller mini-summit and
written the ideas seen in the mailing list.

- The place where IO controller should be implemented
  - Block layer in conjunction with the IO scheduler
  - Common layer right above the IO scheduler
  - CFQ enhancement.
  - Both block and common layer, users can select whichever controller
    they want.
  - VFS layer

- What kind of bandwidth control policies are needed?
  - Proportional weight
  - Enforcing upper limit
  - Minimum bandwidth guarantee

- How to handle buffered writes?
  - Add dirt-ratio in the memory controller
  - Add bufferred-write-cgroup to track buffered writebacks
  - A per group per bdi pdflush threads

- Who should be charged for swap activity?
  - who requests a page.
  - who has a page.
  - All swap activities are charged to the root group.

And I would also like to discuss about the followings.

- Extensions of struct bio
  - Make a bio point to the io_context of a process which creates the
    I/O request. This allows to pass the IO scheduling class and
    priority information to IO controller even if the IO is submitted
    by another process which does not create the request, such as a
    worker thread.
  - Add a new flag to struct bio to identify the bio as urgent. This
    gives IO controller a chance to handle the bio as high
    priority. This flag should be set if the bio is created for the
page-out operation.
- Common test methods to verify the functionality of IO controller.

Please give me comments and suggestions. I may be missing or
misunderstanding something.

Ryo Tsuruta
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