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 GzePzkbA G45vA0H8UdbzfTQ9dLAnxc3Gt0sVjANPDHyOjZpe5zSRUaOSkbc7s4GuOWnv1b48NWn63aLwUaOkzEf/+eDWIyHRgVw7YMVJ0SPScAJ82oAPXvISG/iyK9iumyWvI2n4BqWgPjeUW9bi7nWfFc8e02jKJHe1iIyxSEj8gV+EUrK8GoUvJys8NAV84K+lqSq+k3NoU4QyOIEfhcocqswFaa0uTj6RMapJdvlIMD1575tMzRsJI3pKOOCcPf5uxWOwsQYFpkGCzQtCK2/eRba65zeigVYevnA2pKFDrANCUR/o+PNAM7cVuJZyOC79eg04s1dQltSZdspS02rVkuLLGZgF2qzysZFsiLpBvBdvyl9Av1ILIM0NXO+fuX5mCvhx3o7zZdkibfBIW2HU+fncIidPtPQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 4/10/2023 10:47 AM, Joao Martins wrote: > > > On 10/04/2023 18:27, Jane Chu wrote: >> >> On 4/8/2023 3:19 AM, Aneesh Kumar K.V wrote: >>> Jane Chu writes: >>> >>>> On 4/7/2023 5:23 AM, Aneesh Kumar K.V wrote: >>>>> diff --git a/mm/Kconfig b/mm/Kconfig >>>>> index ff7b209dec05..99f87c1be1e8 100644 >>>>> --- a/mm/Kconfig >>>>> +++ b/mm/Kconfig >>>>> @@ -461,6 +461,9 @@ config SPARSEMEM_VMEMMAP >>>>>          pfn_to_page and page_to_pfn operations.  This is the most >>>>>          efficient option when sufficient kernel resources are available. >>>>>    +config ARCH_WANT_OPTIMIZE_VMEMMAP >>>>> +    bool >>>>> + >>>> >>>> Could this devdax specific config switch be added to drivers/dax/Kconfig >>>> ? also, how about adding 'DAX' to the config switch name? >>> >>> I would say we want to make it more generic. ie, both hugetlb and devdax >>> can now derive the feature support via ARCH_WANT_OPTIMIZE_VMEMAP >> >> The two config switches have different purposes, it's better to keep them >> separate.  For example, recent hugetlb high granularity mapping (HGM) project >> requires to users to make a choice between HGM and hugetlb vmemmap >> optimization(at least for now), while one can keep devdax compound page support >> enabled. >> > > Is it done by kconfig? If it helps: > > * there's a static key hugetlb can use to tell if this is enabled or not like > how page_fixed_fake_head() uses it: > > if (!static_branch_unlikely(&hugetlb_optimize_vmemmap_key)) > ... > > * there's a hugetlb page bit for that vmemmap optimized pages with > HpageOptimized(page). > > * there is a separate hugetlb CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP which is not > the same as the ARCH kconfig. > > But perhaps there's some relevance in the ARCH_HUGETLB specific to HGMv2 that I > am unaware. > Looks like there is no consumer of CONFIG_ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP. There are three ways to enable HVO via CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON alone, or a combination of CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP and boot param 'vmemmap_optimize_enabled' or sysctl variable /proc/sys/vm/hugetlb_optimize_vmemmap. It seems that the devdax compound page support does not cross path with HVO which has a lot more moving arms, and so it's better to keep the devdax config switch local to devdax and leave HVO alone. thanks! -jane