Messages in this thread | | | Date | Fri, 02 Mar 2007 20:27:06 -0800 (PST) | Subject | Re: [PATCH 1/9] ioatdma: Push pending transactions to hardware more frequently | From | David Miller <> |
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From: Jeff Garzik <jeff@garzik.org> Date: Fri, 02 Mar 2007 22:14:39 -0500
> 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?
In fact I think this has been tweaked twice in the vanilla tree already. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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