Rare project developers

[Frédéric LOUI <>]

Hi,

Based on the ptf tests provided. INTEL concluded that this is more a global 
bug ( WRT TOFINO 1 & TOFINO 2) related to PHV allocation during p4c 
compilation.
This p4c « corner case » bug would most likely be visible on TOFINO 2. 
--dead-code-elimination is a trigger that would change PHV allocation and 
thus would more likely hide the bug instead of correcting it.

> If so, I will add the --no-dead-code-elimination flag to the build
> procedure for Tofino2-based platforms in the rare-nix repo.

IIUC, this can result in having a correct PHV allocation that would not yield 
the bug.
TBH this is not 100% sure that this PHV allocation would be correct for all 
RARE profile,

> If so, I will add the --no-dead-code-elimination flag to the build
> procedure for Tofino2-based platforms in the rare-nix repo.

Yes for now, we have nothing better than adding «  --no-dead-code-elimination 
» flag.
Good news is that we will be able to test all of them either with TNA2 model 
but also we should have received 2xTOFINO2 switch in Geneva.

> My previous workaround (commit 09e14ee4 in the rare repo) only worked
> on the model but not on the ASIC. I notice that it has already been
> removed by the combination of commits 5b0e759 and 3d6d736. That's fine
> but I'm not sure if it was intentional (I'm still unhappy with these
> automated commits...).

MMhh … What you are mentioning is interesting. This would mean that PHV 
allocation has somewhat a runtime behaviour or is BSP related.

Anyway, more importantly, _WELCOME_BACK_ !

I’m on leave but feel free to move forward with your build. 
Xavier is eager to move forward with newest freeRtr (tna-experimental) 
release that would help debug LAG at the dataplane level.

All the best,
Frederic

> Le 15 déc. 2022 à 13:25, Alexander Gall <> a écrit :
> 
> Hi Frédéric
> 
> Thanks for helping to debug the issue with the dropped packets on
> Tofino2. Do I understand correctly that disabling dead-code
> eliminiation when compiling for Tofino2 is a workaround for this
> problem until Intel fixes the bug (P4C-5045) in the compiler?
> 
> If so, I will add the --no-dead-code-elimination flag to the build
> procedure for Tofino2-based platforms in the rare-nix repo.
> 
> My previous workaround (commit 09e14ee4 in the rare repo) only worked
> on the model but not on the ASIC. I notice that it has already been
> removed by the combination of commits 5b0e759 and 3d6d736. That's fine
> but I'm not sure if it was intentional (I'm still unhappy with these
> automated commits...).
> 
> -- 
> Alex