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    SubjectRe: [RFC PATCH 0/5] Memory access profiler(IBS) driven NUMA balancing
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    On 2/9/23 20:28, Bharata B Rao wrote:
    > On 2/9/2023 7:58 PM, Dave Hansen wrote:
    >> On 2/8/23 22:04, Bharata B Rao wrote:
    >>>> First, IIRC, Intel PEBS at the time only gave guest virtual addresses in
    >>>> the PEBS records. They had to be translated back to host addresses to
    >>>> be usable. That was extra expensive.
    >>> Just to be clear, I am using IBS in host only and it can give both virtual
    >>> and physical address.
    >> Could you talk a little bit about how IBS might get used for NUMA
    >> balancing guest memory?
    > IBS can work for guest, but will not provide physical address. Also
    > the support for virtualized IBS isn't upstream yet.
    >
    > However I am not sure how effective or useful NUMA balancing within a guest
    > is, as the actual physical addresses are transparent to the guest.
    >
    > Additionally when using IBS in host, it is possible to prevent collection
    > of samples from secure guests by using the PreventHostIBS feature.
    > (https://lore.kernel.org/linux-perf-users/20230206060545.628502-1-manali.shukla@amd.com/T/#)
    I was wondering specifically about how a host might use IBS to balance
    guest memory transparently to the guest. Now how a guest might use IBS
    to balance its own memory.

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