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    SubjectRe: [PATCH v2 5/6] powerpc/pseries/iommu: Make use of DDW even if it does not map the partition
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    On Wed, 2020-06-24 at 03:24 -0300, Leonardo Bras wrote:
    > As of today, if a DDW is created and can't map the whole partition, it's
    > removed and the default DMA window "ibm,dma-window" is used instead.
    >
    > Usually this DDW is bigger than the default DMA window, so it would be
    > better to make use of it instead.
    >
    > Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
    > ---

    I tested this change with a 256GB DDW which did not map the whole
    partition, with a MT27700 Family [ConnectX-4 Virtual Function].

    I noticed the performance improvement is about the same as using DDW
    with IOMMU bypass.

    64 thread write throughput: +203.0%
    64 thread read throughput: +17.5%
    1 thread write throughput: +20.5%
    1 thread read throughput: +3.43%
    Averag
    e write latency: -23.0%
    Average read latency: -2.26%


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