Message ID | 20241106155847.7985-3-gourry@gourry.net |
---|---|
State | New |
Headers | show |
Series | memory,x86,acpi: hotplug memory alignment advisement | expand |
Gregory Price wrote: > 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) if no hotplug advice: Max block size if system is bare-metal, > otherwise use end of memory alignment. > 4) if hotplug advice: lesser of advice and end of memory alignment. This seems like documentation that also belongs in-line in the code. Perhaps a follow-on to add this to memory_block_advised_max_size()? For this one: Acked-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index ff253648706f..2622dc7c78ba 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -1452,16 +1452,21 @@ static unsigned long probe_memory_block_size(void) } /* - * Use max block size to minimize overhead on bare metal, where - * alignment for memory hotplug isn't a concern. + * When hotplug alignment is not a concern, maximize blocksize + * to minimize overhead. Otherwise, align to the lesser of advice + * alignment and end of memory alignment. */ - if (!boot_cpu_has(X86_FEATURE_HYPERVISOR)) { + bz = memory_block_advised_max_size(); + if (!bz) { bz = MAX_BLOCK_SIZE; - goto done; + if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR)) + goto done; + } else { + bz = max(min(bz, MAX_BLOCK_SIZE), MIN_MEMORY_BLOCK_SIZE); } /* Find the largest allowed block size that aligns to memory end */ - for (bz = MAX_BLOCK_SIZE; bz > MIN_MEMORY_BLOCK_SIZE; bz >>= 1) { + for (; bz > MIN_MEMORY_BLOCK_SIZE; bz >>= 1) { if (IS_ALIGNED(boot_mem_end, bz)) break; }