IPMI SOL performance

[Tom Joseph]

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