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    SubjectRe: [Xen-devel] [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux
    On 14/09/15 12:32, Arnd Bergmann wrote:
    > On Monday 14 September 2015 13:04:59 Roger Pau Monné wrote:
    >>> TBH, I'm expecting a small impact to the performance. It would be hard
    >>> to get the exactly the same performance as today if we keep the helpers
    >>> to avoid the backend dealing himself with the splitting and page
    >>> granularity.
    >>>
    >>> Although, if the performance impact is not acceptable, it may be
    >>> possible to optimize gnttab_foreach_grant_in_range by moving the
    >>> function inline. The current way to the loop is the fastest I've found
    >>> (I've wrote a small program to test different way) and we will need it
    >>> when different of size will be supported.
    >>
    >> I don't expect the performance to drop massively with this patches
    >> applied, but it would be good to al least have an idea of the impact.
    >
    > Note that using 64kb pages in Linux tends to destroy performance
    > in Linux in any case, as the memory consumption for most workloads
    > explodes. In a virtualized environment you already tend to be
    > memory constrained, so any measurement should take that into account
    > and put the extra overhead into perspective to the massive overhead
    > of running 64kb pages when RAM is tight.

    If this is the case, why are some distros using 64 KiB pages then?

    David


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