On Tue, Apr 20, 2021 at 6:35 PM Oscar Salvador <osalvador@xxxxxxx> wrote:
>
> On Thu, Apr 15, 2021 at 04:40:04PM +0800, Muchun Song wrote:
> > bool mhp_supports_memmap_on_memory(unsigned long size)
> > {
> > + bool supported;
> > unsigned long nr_vmemmap_pages = size / PAGE_SIZE;
> > unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
> > unsigned long remaining_size = size - vmemmap_size;
> > @@ -1011,11 +1012,18 @@ bool mhp_supports_memmap_on_memory(unsigned long size)
> > * altmap as an alternative source of memory, and we do not exactly
> > * populate a single PMD.
> > */
> > - return memmap_on_memory &&
> > - IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) &&
> > - size == memory_block_size_bytes() &&
> > - IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
> > - IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT);
> > + supported = memmap_on_memory &&
> > + IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) &&
> > + size == memory_block_size_bytes() &&
> > + IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
> > + IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT);
> > +
> > + if (supported && is_hugetlb_free_vmemmap_enabled()) {
> > + pr_info("Cannot enable memory_hotplug.memmap_on_memory, it is not compatible with hugetlb_free_vmemmap\n");
> > + supported = false;
> > + }
>
> I would not print anything and rather have
>
> return memmap_on_memory &&
> !is_hugetlb_free_vmemmap_enabled &&
> IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) &&
> size == memory_block_size_bytes() &&
> IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
> IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT);
OK. Will do.
>
> Documentation/admin-guide/kernel-parameters.txt already provides an
> explanation on memory_hotplug.memmap_on_memory parameter that states
> that the feature cannot be enabled when using hugetlb-vmemmap
> optimization.
>
> Users can always check whether the feature is enabled via
> /sys/modules/memory_hotplug/parameters/memmap_on_memory.
If memory_hotplug.memmap_on_memory is enabled
$ cat /sys/module/memory_hotplug/parameters/memmap_on_memory
$ Y
If memory_hotplug.memmap_on_memory is disabled
$ cat /sys/module/memory_hotplug/parameters/memmap_on_memory
$ N
>
> Also, I did not check if it is, but if not, the fact about hugetlb-vmemmmap vs
> hotplug-vmemmap should also be called out in the hugetlb-vmemmap kernel
> parameter.
Make sense. I will update the doc.
Thanks.
>
> Thanks
>
> --
> Oscar Salvador
> SUSE L3
