On 20.02.25 20:35, Gregory Price wrote:
On Thu, Feb 20, 2025 at 08:26:21PM +0100, David Hildenbrand wrote:
On 20.02.25 19:43, Gregory Price wrote:
There were ideas in how to optimize that (e.g., requiring a new sysfs
interface to expose variable-sized blocks), if anybody is interested, please
reach out.
Multiple block sizes would allow managing the misaligned issues I
discussed earlier as well (where a memory region is not aligned to the
arch-preferred block size). At least in that scenario, the misaligned
regions could be brought online as minimal block size (256MB) while the
aligned portions could be brought online in larger (2GB) chunks.
Do you think this would this require a lot of churn to enable? Last I dug
through hotplug, it seemed to assume block sizes would be uniform. I was
hesitant to start ripping through it.
There were some discussions around variable-sized memory blocks. But we
cannot rip out the old stuff, because it breaks API and thereby Linux
user space. There would have to be a world switch (e.g., kernel cmdline,
config option)
... and some corner cases are rather nasty (e.g., hotunplugging boot
memory, where we only learn from ACPI which regions actually belong to a
single DIMM; dlpar hotunplugging individual memory blocks of boot memory
IIRC).
--
Cheers,
David / dhildenb
