On Tue, Oct 29, 2024 at 01:40:38PM +0100, David Hildenbrand wrote:
> On 22.10.24 23:34, 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.
> >
> > Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> > Signed-off-by: Gregory Price <gourry@xxxxxxxxxx>
> > ---
> > arch/x86/mm/init_64.c | 14 +++++++++-----
> > 1 file changed, 9 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> > index ff253648706f..93d669f467f7 100644
> > --- a/arch/x86/mm/init_64.c
> > +++ b/arch/x86/mm/init_64.c
> > @@ -1452,13 +1452,17 @@ 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_probe_max_size();
> > + if (!bz) {
> > bz = MAX_BLOCK_SIZE;
> > - goto done;
> > - }
> > + if (!boot_cpu_has(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) {
^^^^^^^^^^^^^^^^^^^^^^^^
>
>
> Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Will pick this up but wanted to point out the silly bug above.
This version completely ignores the advise lol.
Changing to below
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 93d669f467f7..01876629f21f 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1465,7 +1465,7 @@ static unsigned long probe_memory_block_size(void)
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;
}
>
> --
> Cheers,
>
> David / dhildenb
>
