On Wed, Apr 21, 2021 at 3:33 PM Oscar Salvador <osalvador@xxxxxxx> 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
