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    Subject[PATCH 1/7] [I/OAT] Push pending transactions to hardware more frequently
    Date
    Every 20 descriptors turns out to be to few append commands with
    newer/faster CPUs. Pushing every 4 still cuts down on MMIO writes to an
    acceptable level without letting the DMA engine run out of work.

    Signed-off-by: Chris Leech <christopher.leech@intel.com>
    ---

    drivers/dma/ioatdma.c | 4 ++--
    1 files changed, 2 insertions(+), 2 deletions(-)

    diff --git a/drivers/dma/ioatdma.c b/drivers/dma/ioatdma.c
    index dbd4d6c..be4fdd7 100644
    --- a/drivers/dma/ioatdma.c
    +++ b/drivers/dma/ioatdma.c
    @@ -310,7 +310,7 @@ static dma_cookie_t do_ioat_dma_memcpy(s
    list_splice_init(&new_chain, ioat_chan->used_desc.prev);

    ioat_chan->pending += desc_count;
    - if (ioat_chan->pending >= 20) {
    + if (ioat_chan->pending >= 4) {
    append = 1;
    ioat_chan->pending = 0;
    }
    @@ -818,7 +818,7 @@ static void __devexit ioat_remove(struct
    }

    /* MODULE API */
    -MODULE_VERSION("1.7");
    +MODULE_VERSION("1.9");
    MODULE_LICENSE("GPL");
    MODULE_AUTHOR("Intel Corporation");

    -
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