Re: The performance and behaviour of the anti-fragmentation relatedpatches

[KAMEZAWA Hiroyuki]

On Thu, 1 Mar 2007 21:11:58 -0800 (PST)
Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> The whole DRAM power story is a bedtime story for gullible children. Don't 
> fall for it. It's not realistic. The hardware support for it DOES NOT 
> EXIST today, and probably won't for several years. And the real fix is 
> elsewhere anyway (ie people will have to do a FBDIMM-2 interface, which 
> is against the whole point of FBDIMM in the first place, but that's what 
> you get when you ignore power in the first version!).
> 

At first, we have memory hot-add now. So I want to implement hot-removing 
hot-added memory, at least. (in this case, we don't have to write invasive
patches to memory-init-core.)

Our(Fujtisu's) product, ia64-NUMA server, has a feature to offline memory.
It supports dynamic reconfigraion of nodes, node-hoplug.

But there is no *shipped* firmware for hotplug yet. RHEL4 couldn't boot on
such hotplug-supported-firmware...so firmware-team were not in hurry.
It will be shipped after RHEL5 comes.
IMHO, a firmware which supports memory-hot-add are ready to support memory-hot-remove
if OS can handle it.

Note:
I heard embeded people often designs their own memory-power-off control on
embeded Linux. (but it never seems to be posted to the list.) But I don't know
they are interested in generic memory hotremove or not.

Thanks,
-Kame



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