Re: [Xen-devel] Taking on a Xen development project

[Joshua Otto <jtotto@xxxxxxxxxxxx>]

On Sat, Dec 12, 2015 at 11:02:50PM +0000, Andrew Cooper wrote:
> On 12/12/2015 22:30, Joshua Otto wrote:
> > On Sat, Dec 12, 2015 at 10:19:31AM +0800, Yang Hongyang wrote:
> >> On 2015å12æ11æ 01:23, Andrew Cooper wrote:
> >>> Hello - thankyou for your interest.
> >>>
> >>> One area to look at might be the parameters to the live migration
> >>> looping.  As part of the migration v2 rework I did in the 4.6 dev
> >>> period, I left all of that alone, and it is in a working but poor state.
> >>>
> >>> In the past, there have been several research investigations into
> >>> improving the live migration algorithm, such as tracking the rate of
> >>> dirtying of memory, or attempting to resume the domain on the far side
> >>> and fault the final memory across.
> >> I think you mean postcopy here? The hypervisor then needs to maintain
> >> a dirty page bitmap and generate pagefault when a page is not yet
> >> tranferred to the far end.
> >> This feature already merged into QEMU2.5(kvm patch which generates
> >> pagefault also been merged into linux kernel mainline), if you want a
> >> reference, you can take a look at those patches.
> >> This surely is a great aera to work on.
> >>
> >>> If you are interested in perusing this, start with reading
> >>> docs/features/migration.pandoc in the Xen tree.
> > We'd definitely be interested in working on live migration!  The feature
> > is essentially an implementation of the approach described in Section
> > 5.1 of [0], right?
> 
> Yes - Section 5.1 is quite a good general description of live migration
> (even after my white-room redesign from first principles), although be
> aware that some of the more technical details are now out of date.
> 
> >
> > Would the focus of the project be to implement and evaluate postcopy
> > live migration in Xen, then, or to more generally build on previous
> > research efforts? (either way sounds like fun!)
> 
> I hadn't really though that far ahead.  I was more suggestion that the
> general area of live migration has a lot in the way to offer for
> projects, be it implementing someone else's research, or researching a
> new area yourself.
> 
> There are definitely areas where improvements can be made, and some of
> these would be an easier introduction to the codebase than to start with
> a full postcopy implementation.  (Not that I wish to put you off
> postcopy, but it does come with a number of non-trivial problems to
> solve as part of getting the scaffolding in place.)

Ah, okay.  Would our best path forward then be to gain enough technical
familiarity with the feature and past research to come back and propose
a more specific project on the list?

Thank you for all of your help!

Josh

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