Is there any way how to profile what is driver doing on low level ..oprofile
is probably too highlevel although it could help.
I've got through source code that rx_missed_errors is counter that sums up
RXMPC stats register....reasons mentioned there are
1) insufficient buffers allocate
2) insufficient bandwidth on the IO bus
ad 1) ethtool -G eth0 rx 4096 does not solve this issue at all - if i
understand this should increase rx ring buffers 8 times => then there is
problem how often DMA stores these buffers into operating memory - but i
cannot modify any other coalesce parametrs to see if that can be helped..
ad 2) no idea how to see utilization of PCI-express bus :/...google did not
help with this :). I've got supermicro x8dah motherboard with enough PCI-E
2.0 slots...intel card is plugged into x8 lane slot:
LnkSta: Speed 5GT/s, Width x8, TrErr- Train- SlotClk+ DLActive-
BWMgmt- ABWMgmt-
Unidirectional bandwidth should be 32Gbps - lets say pci-e protocol has 20%
overhead that gives us still much more than 20Gbps for one direction =>
40Gbps fullduplex.
I guess we dont have to discuss if QPI is sufficient for one 10GE port :)
thanks for any hints...its just killing me ;)
Radim
On Thu, May 19, 2011 at 1:02 AM, [email protected] <
[email protected]> wrote:
> Hi,
>
> I already dont know where to ask...so I will try it here :)...my problem is
> called *rx_missed_errors* :), i've spent days trying to tune it somehow
> but still with no success.
>
> I've got 2 pretty nice computers - NUMA - 2x Xeon 5620 (quad-core)...2x
> dual port 10GE NIC - Intel 82599 controller..
>
> Lets imagine very simple scenario:
>
> generator - sink
>
> where generator and switch are computers running Linux 2.6.39 with 3.3.9
> ixgbe driver
>
> Using pktgen i generate 64B packets...lets say 10 Mpps - receiving port at
> sink.
>
> I generated 100M pacekts.
>
> smp affinity is configured
> flow control is off
>
> At sink check ethtool -S eth0
>
> NIC statistics:
> rx_packets: 68097737
> rx_missed_errors: 31902263
> rx_pkts_nic: 68097737
>
> Received packets are nicely balanced between 16 Rx queues...but 31M packets
> is lost. CPUs are idle 90% times (you can check attached mpstat-rx.txt)
>
> I wanted to tune a bit interrupt coalesce - but ethtool -C eth0 does not
> allow me to set anything else than rx-usecs - i've increased it but with no
> luck.
>
> So my questions are:
>
> 1) is there any way how to tune interrupt moderation?
>
> 2) Am I missing something?? I would expect that since all cores are mostly
> idle there should be a way how to tune driver so it actually can perform
> well even under heavy load with 64B packets.
>
> 3) Another scenario is generator - (eth0)bridge - sink....in this case
> there is 84% packet loss!! at the receiving interface and CPU cores are
> still mostly idle (90%)
>
>
> Please if you could help me a bit...I would be very happy :). Its almost
> matter of life..
>
> Thanks
> Radim
>
>
>
>
>
> --
> Radim Roška
--
Radim Roška
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