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[dm-devel] Re: [PATCH 0/8] I/O bandwidth controller and BIO tracking

On Thu, 13 Nov 2008 12:10:19 +0900 (JST)
Ryo Tsuruta <ryov valinux co jp> wrote:

> Hi everyone,
> This is a new release of dm-ioband and bio-cgroup. With this release,
> the overhead of bio-cgroup is significantly reduced and the accuracy
> of block I/O tracking is much improved. These patches are for
> 2.6.28-rc2-mm1.

>From my point of view, a way to record bio_cgroup_id to page_cgroup is quite neat
and nice.

My concern is "bio_cgroup_id". It's provided only for bio_cgroup.
In this summer, I tried to add swap_cgroup_id only for mem+swap controller but
commenters said "please provide "id and lookup" in cgroup layer, it should be useful."
And I agree them. (and postponed it ;)

Could you try "id" in cgroup layer ? How do you think, Paul and others ?

That's my only concern and if I/O controller people decides to live with
this bio tracking infrastracture,
   page -> page_cgroup -> bio_cgroup_id
I have no objections. And enqueue necessary changes to my queue.


> Enjoy it!
> dm-ioband
> =========
> Dm-ioband is an I/O bandwidth controller implemented as a
> device-mapper driver, which gives specified bandwidth to each job
> running on the same block device. A job is a group of processes
> or a virtual machine such as KVM or Xen. 
> I/O throughput on dm-ioband is excellent not only on SATA storage
> but on SDD, which as good as the one without dm-ioband.
> Changes from the previous release:
>   - Fix a bug that create_workqueue() is called during spin lock
>     when creating a new ioband group.
>   - A new tunable parameter "carryover" is added, which specifies
>     how many tokens an ioband group can keep for the future use
>     when the group isn't so active.
>   - Other policies to schedule BIOs.
>     - Policies which fits SSD.
>      e.g.)
>        - Guarantee response time.
>        - Guarantee throughput.
>     - Policies which fits Highend Storage or hardware raid storage.
>        - Some LUNs may share the same bandwidth.
>   - Support WRITE_BARRIER when the device-mapper layer supports it.
>   - Implement the algorithm of dm-ioband in the block I/O layer
>     experimentally.
> bio-cgroup
> ==========
> Bio-cgroup is a BIO tracking mechanism, which is implemented on the
> cgroup memory subsystem. With the mechanism, it is able to determine
> which cgroup each of bio belongs to, even when the bio is one of
> delayed-write requests issued from a kernel thread such as pdflush.
> Changes from the previous release:
>   - This release is a new implementation.
>   - This is based on the new design of the cgroup memory controller
>     framework, which pre-allocates all cgroup-page data structures to
>     reduce the overhead.
>   - The overhead to trace block I/O requests is much smaller than that
>     of the previous one. This is done by making every page have the id
>     of its corresponding bio-cgroup instead of the pointer to it and
>     most of spin-locks and atomic operations are gone.
>   - This implementation uses only 4 bytes per page for I/O tracking
>     while the previous version uses 12 bytes on a 32 bit machine and 24
>     bytes on a 64 bit machine.
>   - The accuracy of I/O tracking is improved that it can trace I/O
>     requests even when the processes which issued these requests get
>     moved into another bio-cgroup.
>   - Support bounce buffers tracking. They will have the same bio-cgroup
>     owners as the original I/O requests.
>   - Support to track I/O requests that will be generated in Linux
>     kernel, such as those of RAID0 and RAID5.
> A list of patches
> =================
> The following is a list of patches:
>   [PATCH 0/8] I/O bandwidth controller and BIO tracking
>   [PATCH 1/8] dm-ioband: Introduction
>   [PATCH 2/8] dm-ioband: Source code and patch
>   [PATCH 3/8] dm-ioband: Document
>   [PATCH 4/8] bio-cgroup: Introduction
>   [PATCH 5/8] bio-cgroup: The new page_cgroup framework
>   [PATCH 6/8] bio-cgroup: The body of bio-cgroup
>   [PATCH 7/8] bio-cgroup: Page tracking hooks
>   [PATCH 8/8] bio-cgroup: Add a cgroup support to dm-ioband
> Please see the following site for more information:
>   Linux Block I/O Bandwidth Control Project
>   http://people.valinux.co.jp/~ryov/bwctl/
> Thanks,
> Ryo Tsuruta

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