On Fri, Mar 05, 2021 at 04:35:08PM +0100, David Hildenbrand wrote:
> On 04.03.21 11:00, Oscar Salvador wrote:
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index 04545725f187..e626dab39c60 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -2794,6 +2794,20 @@
> > seconds. Use this parameter to check at some
> > other rate. 0 disables periodic checking.
> > + memory_hotplug.memmap_on_memory
> > + [KNL,X86,ARM] Boolean flag to enable this feature.
>
> Right now it can be set on any arch with memory hotplug, right? It's simply
> not effective.
Right.
> > + Format: {on | off (default)}
> > + When enabled, memory to build the pages tables for the
> > + memmap array describing the hot-added range will be taken
> > + from the range itself, so the memmap page tables will be
> > + self-hosted.
> > + Since only single memory device ranges are supported at
> > + the moment, this option is disabled by default because
> > + it might have an impact on workloads that needs large
> > + contiguous memory chunks.
> > + The state of the flag can be read in
> > + /sys/module/memory_hotplug/parameters/memmap_on_memory.
>
> Maybe want to add that even if enabled, there are cases where it is not
> effective?
Sure, I already added a hint.
> > +static bool memmap_on_memory __ro_after_init;
> > +module_param(memmap_on_memory, bool, 0444);
> > +MODULE_PARM_DESC(memmap_on_memory, "Enable memmap on memory for memory hotplug");
>
> Wondering if this makes sense getting wrapped in
>
> #ifdef CONFIG MHP_MEMMAP_ON_MEMORY
>
> just a thought.
Definitely, will wrapp it with MHP_MEMMAP_ON_MEMORY.
>
> LGTM
>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Thanks!
--
Oscar Salvador
SUSE L3
