On 12.07.23 05:16, Aneesh Kumar K V wrote:
On 7/11/23 10:49 PM, David Hildenbrand wrote:
On 11.07.23 06:48, Aneesh Kumar K.V wrote:
Add a new kconfig option that can be selected if we want to allow
pageblock alignment by reserving pages in the vmemmap altmap area.
This implies we will be reserving some pages for every memoryblock
This also allows the memmap on memory feature to be widely useful
with different memory block size values.
"reserving pages" is a nice way of saying "wasting memory". :) Let's spell that out.
I think we have to find a better name for this, and I think we should have a toggle similar to memory_hotplug.memmap_on_memory. This should be an admin decision, not some kernel config option.
memory_hotplug.force_memmap_on_memory
"Enable the memmap on memory feature even if it could result in memory waste due to memmap size limitations. For example, if the memmap for a memory block requires 1 MiB, but the pageblock size is 2 MiB, 1 MiB
of hotplugged memory will be wasted. Note that there are still cases where the feature cannot be enforced: for example, if the memmap is smaller than a single page, or if the architecture does not support the forced mode in all configurations."
Thoughts?
With module parameter, do we still need the Kconfig option?
No.
Sleeping over this, maybe we can convert the existing
memory_hotplug.memmap_on_memory parameter to also accept "force".
--
Cheers,
David / dhildenb
