Messages in this thread | | | Date | Fri, 02 Mar 2007 22:14:39 -0500 | From | Jeff Garzik <> | Subject | Re: [PATCH 1/9] ioatdma: Push pending transactions to hardware more frequently |
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Chris Leech wrote: > 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 8e87261..0f77a9d 100644 > --- a/drivers/dma/ioatdma.c > +++ b/drivers/dma/ioatdma.c > @@ -310,7 +310,7 @@ static dma_cookie_t do_ioat_dma_memcpy(struct ioat_dma_chan *ioat_chan, > 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) {
This sounds like something that will always be wrong -- or in other words, always be right for only the latest CPUs. Can this be made dynamic, based on some timing factor?
Jeff
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