IPMI SOL performance

[Tom Joseph]

   Related issue -  https://github.com/openbmc/openbmc/issues/2958

On Monday 19 March 2018 04:43 PM, Tom Joseph wrote:
> Hello,
>
> I wanted to discuss about an issue related to IPMI SOL. Petitboot has 
> a menu to select the boot option, it has a timeout after which the 
> default boot option is selected and boot continues.The observation is 
> that when verbose debug traces are enabled in the hostboot, by the 
> time petitboot options are printed on the SOL console the menu timeout 
> expires and the user is not able to change the boot option.
>
> The same issue is not hit by the ssh console on port 2200 and does not 
> miss the timeout of the petitboot menu option.
>
> IPMI uses UDP protocol and the maximum size of the  SOL payload per 
> packet according to the specification is 255 bytes. Also the ack for 
> each of the IPMI packet requires a command lookup
> and execution. Compared with IPMI SOL, ssh supports 64kb payloads and 
> ack does not need an application lookup, so the round-trip timing is 
> faster. IPMI specification for SOL is written with UART speed as 
> reference, but the VUART pushes the data at a much faster rate.
>
> One suggestion that I came across support an OEM payload size for SOL, 
> which is higher than 255 bytes, to get a better throughput. Please do 
> share other ideas to tackle this problem and improve performance.
>
> Regards,
> Tom
>