Messages in this thread | | | Date | Wed, 21 Apr 2021 09:33:52 +0200 | From | Oscar Salvador <> | 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 Wed, Apr 21, 2021 at 11:41:24AM +0800, Muchun Song wrote: > > 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.
Heh, I realized this is not completely true. Users can check whether the feature is __enabled__ by checking the sys fs, but although it is enabled, it might not be effective.
This might be due to a different number of reasons, vmemmap does not fully span a PMD, the size we want to add spans more than a single memory block, etc.
That is what
"Note that even when enabled, there are a few cases where the feature is not effective."
is supposed to mean.
Anyway, I did not change my opionion on this.
Thanks
-- Oscar Salvador SUSE L3
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