On 09/09/2014 09:16 AM, Boaz Harrosh wrote:

On 08/22/2014 05:36 PM, Dave Hansen wrote:

quoted

Is there a reason you don't just do this at boot and have to use hotplug
at runtime for it?  

This is a plug and play thing. This memory region is not reached via memory
controller, it is on the ACPI/SBUS device with physical address/size specified
there. On load of block-device this will be called. Also a block device can
be unloaded and should be able to cleanup.

OK, cool.

quoted

What are the ratio of pmem to RAM?  Is it possible
to exhaust all of RAM with 'struct page's for pmem?

Yes! in the not very distant future there will be systems that have only pmem.
yes no RAM. This is because once available some pmem has much better power
efficiency then DRAM, because of the no refresh thing. So even cellphones and
embedded system first.

...

So the Admin/setup will need to calculate and configure the proper ratio of
volatile vs non-volatile portions of its system for proper usage.

I'm just worried that somebody will plug a card in, and immediately OOM
the system.  Or, even worse, a card gets plugged in and 98% of the RAM
gets used by this prd driver and the kernel performs horribly.

I think we probably need to have some tracking of how much memory is
getting used for these mem_map[]s, and make sure they don't get out of hand.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>