Messages in this thread | | | From | Muchun Song <> | Date | Wed, 21 Apr 2021 11:41:24 +0800 | Subject | Re: [External] Re: [PATCH v20 8/9] mm: memory_hotplug: disable memmap_on_memory when hugetlb_free_vmemmap enabled |
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On Tue, Apr 20, 2021 at 6:35 PM Oscar Salvador <osalvador@suse.de> 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
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