Re: [PATCH v8 4/5] app/testpmd: report lcore usage

["Robin Jarry" <rjarry@redhat.com>]

David Marchand, Feb 06, 2023 at 09:58:
> I have been playing a bit with this series with two lcores, each one
> polling a net/null port.
> At first it looked good, but then I started to have one idle lcore, by
> asking net/null not to receive anything.
>
> $ build-clang/app/dpdk-testpmd -c 7 --no-huge -m 40 -a 0:0.0 --vdev
> net_null1,no-rx=1 --vdev net_null2 -- --no-mlockall
> --total-num-mbufs=2048 -ia --record-core-cycles --nb-cores=2
>
> One thing that struck me is that an idle lcore was always showing less
> "total_cycles" than a busy one.
> The more time testpmd was running, the bigger the divergence between
> lcores would be.
>
> Re-reading the API, it is unclear to me (which is the reason for my
> comments on patch 2).
> Let's first sort out my patch 2 comments and we may revisit this patch
> 4 implementation afterwards (as I think we are not accounting some
> mainloop cycles with current implementation).

Indeed, we are not accounting for all cycles. Only the cycles spent in 
the packet_fwd_t functions. This was already the case before my series 
I only added the busy cycles accounting.

However, I agree that this should be updated to take all cycles into 
account (as much as it is possible with the current code base). Maybe 
this could be done as a separate patch or do you want to include it in 
this series?

> A fwd_lcore object is bound to a single lcore, so this lcore_id is 
> unneeded.
[snip]
> You can find which fwd_lcore is mapped to a lcore using existing 
> structures. This requires updating some helper, something like:

I had missed that. Indeed, no need for a new field. I'll address that in 
v9.