Thank you for the prompt response.
My system (default, as far as I know) is set at 262144 (256K). If I
understand correctly, then only packets larger than 256K will go through
ioatdma. The maximum MTU of ixgbe is 16K, IIRC, so the system will never
use ioatdma with this configuration, is that correct?
Thanks,
Scott Silverman | IT | Simplex Investments | 312-360-2444
230 S. LaSalle St., Suite 4-100, Chicago, IL 60604
On Wed, Apr 3, 2013 at 1:33 PM, Tantilov, Emil S
<[email protected]>wrote:
> >-----Original Message-----
> >From: Scott Silverman [mailto:[email protected]]
> >Sent: Wednesday, April 03, 2013 10:45 AM
> >To: [email protected]
> >Subject: [E1000-devel] Issues using ioatdma / DCA
> >
> >I'm trying to get the linux networking stack to start using ioatdma (and,
> >ideally, DCA as well).
> >
> >Despite my efforts, the "/sys/class/dma/dma*chan*/in_use" is never set to
> >1, and the memcpy_count and bytes_transferred stay at 0.
> >
> >I'm working with two systems, one using igb, and the other using ixgbe, I
> >have the same results with both. I've tried the in-kernel igb driver (for
> >82576), as well as the three most recent ixgbe drivers (for 82599EB), same
> >results (though sometimes "in_use" is 5, or 8, instead of 2).
> >
> >What am I missing?
>
> By default only very large packets will go through ioatdma. You can
> control this by setting:
>
> sysctl net.ipv4.tcp_dma_copybreak=<packet size>
>
> if you set it very low (like 1) you should see the byte counter
> incrementing when receiving TCP packets.
>
> Thanks,
> Emil
>
>
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