Messages in this thread | | | Date | Wed, 13 Apr 2022 12:10:51 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH v8 4/4] mm: hugetlb_vmemmap: add hugetlb_optimize_vmemmap sysctl |
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On Wed, 13 Apr 2022 22:47:48 +0800 Muchun Song <songmuchun@bytedance.com> wrote:
> We must add hugetlb_free_vmemmap=on (or "off") to the boot cmdline and > reboot the server to enable or disable the feature of optimizing vmemmap > pages associated with HugeTLB pages. However, rebooting usually takes a > long time. So add a sysctl to enable or disable the feature at runtime > without rebooting.
Do we really need this feature? Really? What's the use case and what is the end-user value?
Presumably CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP worsens things for some setups/workloads? Please tell us much more about that. What is the magnitude of the deoptimization?
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