Messages in this thread | | | From | Muchun Song <> | Date | Wed, 21 Apr 2021 17:06:20 +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 Wed, Apr 21, 2021 at 3:33 PM Oscar Salvador <osalvador@suse.de> wrote: > > 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.
Right. I have done the test.
> > 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.
Agree. Thanks for your explanations.
> > 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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