[OpenIndiana-discuss] Are there any known problems with OI and jumbo frames MTU 9000

[Flo]

On 01/15/2013 01:00 AM, Jason Matthews wrote:>
 > I use this configuration with no issues. For an MTU of 9000 with 
VLANs  on
 > the host, make sure the switch MTU is set to 9014 or greater.
 >
 > Thanks,
 > j.
 >

Hi Jason,
do you also use Link Aggregation?
Why must I use 9014 on the switch? I thought, that when the MTU is 9000, 
it will behave like MTU 1500.

Why do you use a MTU of 9000? Only for the higher performance or for the 
lower CPU load?


On 01/14/2013 04:43 PM, Jim Klimov wrote:
> Likely yes, there should be a gain - although some experts on the list
> have recently stated, that with modern hardware the difference should
> be negligible. In the past it could have been greater due to slower
> NIC processors, I suppose.
>
>  From my experience with Jumbo on e1000 interfaces, there are flags
> you should set in the driver config file (and reapply after each OS
> upgrade which overwrites this file):
>
> # diff /kernel/drv/e1000g.conf-orig /kernel/drv/e1000g.conf-jumbo
> 52c52,53
> < MaxFrameSize=0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
> ---
>  > #MaxFrameSize=0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
>  > MaxFrameSize=3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3;
>
>
> Or to test without LSO (dunno why we have this, maybe hunted for bugs?)
>
> # diff /kernel/drv/e1000g.conf-orig /kernel/drv/e1000g.conf-jumbo-noLSO
> 52c52,53
> < MaxFrameSize=0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
> ---
>  > #MaxFrameSize=0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
>  > MaxFrameSize=3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3;
> 84a86,88
>  >
>  >       #Disable LSO in e1000g.conf by adding one line:
>  > lso_enable = 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
>
>
> On my OI boxes I see that the default flag value is still zero...
>
>
> After you set these flags to 3 and reboot, you can use the increased
> frame sizes in "ifconfig ... mtu" clauses.
>
> Also take care to verify that all the NICs and switches and OSes on
> each side do indeed support your chosen frame size (i.e. 9000 bytes),
> because there were many different maximum "increased frame sizes"
> supported over time. By using no more than the lowest common size
> supported by all your gear, you'd avoid packet fragmentation and/or
> errors and benefit from Jumbo.
>
> Good luck,
> //Jim

Hi Jim

thank you for your advice!

I don't know, if the broadcom nics are powerfull enough?
I tested the throghput with iperf with MTU 1500 and MTU 9000.
With 1500 I got 945Mbit and with 9000 I got 985Mbit.

With the newest Solaris version, there is no need to edit the driver 
config file. Is this also possible with OIa7 or is it possible to 
activate the new config file without a reboot?