(8/12/13 2:07 PM), Tejun Heo wrote:

Hey,

On Tue, Aug 13, 2013 at 01:01:09AM +0800, Tang Chen wrote:

quoted

Sorry for the misunderstanding.

I was trying to answer your question: "Why can't the kenrel allocate
hotpluggable memory opportunistic ?".

I've used the wrong word, I was meaning best-effort, which is the only
thing we can do anyway given that we have no control over where the
kernel image is linked in relation to NUMA nodes.

quoted

If the kernel has any opportunity to allocate hotpluggable memory in
SRAT, then the kernel should tell users which memory is hotpluggable.

But in what way ?  I think node is the best for now. But a node could
have a lot of memory. If the kernel uses only a little memory, we will
lose the whole movable node, which I don't want to do.

So, I don't want to allow the kenrel allocating hotpluggable memory
opportunistic.

What I was saying was that the kernel should try !hotpluggable memory
first then fall back to hotpluggable memory instead of failing boot as
nothing really is worse than failing to boot.

I don't follow this. We need to think why memory hotplug is necessary.
Because system reboot is unacceptable on several critical services. Then,
if someone set wrong boot option, systems SHOULD fail to boot. At that time,
admin have a chance to fix their mistake. In the other hand, after running
production service, they have no chance to fix the mistake. In general, default
boot option should have a fallback and non-default option should not have a
fallback. That's a fundamental rule.