Re: [dpdk-dev] [PATCH v1 1/6] build: increase default of max lcores to 512

[David Hunt <david.hunt@intel.com>]

On 17/11/2021 3:55 PM, Morten Brørup wrote:
> My microphone was not working during the Techboard meeting, so here goes instead:
>
> Please consider if the default of max 128 assigned lcores suffices for the expected lifetime of the 21.11 LTS, or if the default should be bumped to 512 as suggested.
>
> @David Hunt, do you have idea about the memory cost of increasing from 128 to 512? This seems to be the primary objection.
>
> -Morten


Hi Morten,

I seem to recall that a simple increase from 128 to 512 cores would 
result in an increased static memory footprint of 2.5MBs per 
application, but there were additional patches in the opriginal patch 
set that switch from static allocation to dynamic allocation reducing 
this to a few hundred kilobytes. This was not deemed the best direction, 
so we went with the improvement of informing the user more clearly on 
how to use the command line syntax to use the physical core numbers 
above 128 as lcores in your application.

I believe the thinking is that 128 lcores is plenty for a single 
application, and if there is a case where more than that is needed (for 
a single application), then the default can be over-ridden by changing 
the max_lcores setting and recompiling.

Rgds,
Dave.