Messages in this thread | | | Date | Mon, 8 Mar 2021 16:46:07 +0100 | From | Oscar Salvador <> | Subject | Re: [PATCH v3 3/5] mm,memory_hotplug: Add kernel boot option to enable memmap_on_memory |
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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@redhat.com>
Thanks!
-- Oscar Salvador SUSE L3
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