Re: [Xen-devel] Re: [RFC][PATCH] Basic support for page offline

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 13/02/2009 17:03, "Tim Deegan" <Tim.Deegan@xxxxxxxxxx> wrote:

> I'll leave page_offline_xen.patch to Keir since he's said he'll do it,
> but 700 new lines of code seems like quite a lot -- surely some subsets
> of he existing buddy splitting and merging code could be split out and
> reused?

It could indeed surely be half the size. It's split for some reason into a
chain of about five functions, each of which does a little bit of the work.
Just merge them all together. And unless you have a good reason for
currently expecting to offline large ranges of pages, and can measure a
substantial performance difference, I would actually just offline one page a
at a time -- implement that in a function and call it repeatedly from a for
loop. It will be far less complex and for bad-page offlining should perform
just fine.

Also some comments about what the difference is between offlining, offlined,
and broken would be nice. The change in free_heap_pages() to preserve
PGC_offlining|PGC_broken struck me as particularly worrying -- no sane C
programmer should write it like that, which just makes me more worried about
the verbosity of the rest.

 -- Keir



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