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    SubjectRe: [PATCH] x86/mm: Tracking linear mapping split events since boot
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    On 1/25/21 12:11 PM, Saravanan D wrote:
    > Numerous hugepage splits in the linear mapping would give
    > admins the signal to narrow down the sluggishness caused by TLB
    > miss/reload.
    >
    > One of the many lasting (as we don't coalesce back) sources for huge page
    > splits is tracing as the granular page attribute/permission changes would
    > force the kernel to split code segments mapped to huge pages to smaller
    > ones thereby increasing the probability of TLB miss/reload even after
    > tracing has been stopped.
    >
    > The split event information will be displayed at the bottom of
    > /proc/meminfo
    > ....
    > DirectMap4k: 3505112 kB
    > DirectMap2M: 19464192 kB
    > DirectMap1G: 12582912 kB
    > DirectMap2MSplits: 1705
    > DirectMap1GSplits: 20

    This seems much more like something we'd want in /proc/vmstat or as a
    tracepoint than meminfo. A tracepoint would be especially nice because
    the trace buffer could actually be examined if an admin finds an
    excessive number of these.

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