On 21.10.24 16:46, Gregory Price wrote:
On Mon, Oct 21, 2024 at 01:12:26PM +0200, David Hildenbrand wrote:
Am 16.10.24 um 21:24 schrieb Gregory Price:
Systems with hotplug may provide an advisement value on what the
memblock size should be. Probe this value when the rest of the
configuration values are considered.
The new heuristic is as follows
1) set_memory_block_size_order value if already set (cmdline param)
2) minimum block size if memory is less than large block limit
3) [new] hotplug advise: lesser of advise value or memory alignment
4) Max block size if system is bare-metal
5) Largest size that aligns to end of memory.
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Gregory Price <gourry@xxxxxxxxxx>
---
arch/x86/mm/init_64.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index ff253648706f..b72923b12d99 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1439,6 +1439,7 @@ static unsigned long probe_memory_block_size(void)
{
unsigned long boot_mem_end = max_pfn << PAGE_SHIFT;
unsigned long bz;
+ int order;
/* If memory block size has been set, then use it */
bz = set_memory_block_size;
@@ -1451,6 +1452,21 @@ static unsigned long probe_memory_block_size(void)
goto done;
}
+ /* Consider hotplug advisement value (if set) */
+ order = memblock_probe_size_order();
"size_order" is a very weird name. Just return a size?
memory_block_advised_max_size()
or sth like that?
There isn't technically an overall "max block size", nor any alignment
requirements - so order was a nice way of enforcing 2-order alignment
while also having the ability to get a -1/-EBUSY/whatever out.
I see. But we (MM) just call it "order" then, like pageblock_order,
max_order, compound_order ... but here we use "size everywhere" so I
prefer to just sticking to that.
I can change it if it's a big sticking point - but that's my reasoning.
Simply enforce it when setting the size. We call it "memory_block_size"
everywhere and it's also a power-of-2 etc and sanity-check that in
memory_dev_init().
--
Cheers,
David / dhildenb
