Thank you for your comment.
I'm very glad. :-)
> Yasunori Goto <[email protected]> wrote:
> >
> > I'll post newest patches for memory hotadd with pgdat allocation as V3.
> > There are many changes to make more common code.
>
> General comments:
>
> - Thanks for working against -mm. It can be a bit of a pain, but it
> eases staging and integration later on.
>
> - Please review all the code to check that all those functions which can
> be made static are indeed made static. I see quite a few global
> functions there.
> - Make sure that all functions which can be tagged __meminit are so tagged.
>
> - It would be useful to build a CONFIG_MEMORY_HOTPLUG=n kernel both with
> and without the patchsets and to publish and maintain the increase in
> code size. Ideally that increase will be zero. Probably it won't be,
> and it'd be nice to understand why, and to minimise it.
Ok. I'll check and fix it.
>
> - Arch issues:
>
> - Which architectures is this patchset aimed at and tested on?
IA64.
At least, Fujitsu is making this style hot-add feature
on ia64 box which is named as PrimeQuest.
(SGI or HP might wait it.)
> - Which other architectures might be able to use this code in the
> future? Because we should ask the maintainers of those other
> architectures to take a look at the changes.
I heard from Andi-san that x86-64 will need this.
And ppc64 might use some of my patch.
It depends on ....
- There is Numa box on its architecture.
- One node of NUMA will be hot-added.
> - What locking does node hot-add use? There are quite a few places in
> the kernel which cheerfully iterate across node lists while assuming that
> they won't change. The usage of stop_machine_run() is supposed to cover
> all that, I assume?
If my understanding is correct, there is 2 critical point.
- One is zonelist update, indeed. Stop_machine_run() can
cover it.
- Another is node_online_map and NODE_DATA().
If node_online_map is onlined before that
NODE_DATA() is updated, or before that pgdat is initialized,
kernel might touch uninitialized pgdat.
So, node_set_online() is called at final point.
The old kernel had pgdat->next link list, it was also critial point
for hot-add. But current -mm remove it. So, it is not issue now. :-)
Thanks.
--
Yasunori Goto
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