Re: GRO aggregation

On 09/11/2012 03:41 PM, Shlomo Pongratz wrote:

From: Marcelo Ricardo Leitner [mleitner@redhat.com]
Sent: Tuesday, September 11, 2012 9:20 PM
To: Shlomo Pongratz
Cc: netdev@vger.kernel.org
Subject: Re: GRO aggregation

On 09/11/2012 10:45 AM, Shlomo Pongartz wrote:

quoted

Hi,

I’m checking GRO aggregation with kernel 3.6.0-rc1+ using Intel ixgbe
driver.
The mtu is 1500 and GRO is on and so are SG and RX checksum.
I ran iperf with default setting and monitor the receiver with tcpdump.
The tcpdump shows that the maximal aggregation is 32120 which is 21 * 1500.
In the transmitter side tcpdump shows that TSO works better (~64K).
I did a capture without GRO enabled to see if there was a difference
between any flag
of any two consecutive packets that forced flushing but didn't find
anything.
Is the GRO aggregation can be tuned.

Hi Shlomo,

Have you tried tuning coalescing parameters?

Marcelo


Hi Marcelo

I didn't play with interrupts coalescing.
Do you suggest to increase the value?

Actually it was an idea from top of my mind, I don't know how it applies 
to ixgbe, sorry. But making the NIC hold the packets a bit more should 
make it send larger ones to kernel. Trade-off between latency/throughput.

I was thinking about ethtool -c options, like rx-usecs*

Marcelo