Re: [perfmon2] Forking perfmon2/libpfm into LKML and vendor branches

[William C. <wc...@re...>]

Philip Mucci wrote:
> HI Stefane,
> 
> In light of the recent discussions, I would request as a vendor that  
> we fork perfmon2 into two branches:
> 
> 1) That can be hacked up for the LKML folks into whatever form it needs
> 2) One that runs on a stable kernel platform (I nominate 2.6.22) and  
> that only has bug fixes applied and contains the current supported  
> interface.
> 
> As a vendor, I need a stable platform until this all gets resolved.  
> It is without question that the Perfmon2 interface will change over  
> time to make it into the kernel. SiCortex, SGI, IBM and Cray are  
> wedded to this infrastructure and we need to be able to propagate  
> fixes against a stable base, without worrying about feature removal  
> or linux rev compatibility.
> 
> I do not think this will be much extra work at all, and I'm happy to  
> lend a hand making it happen. This will allow infrastructure  
> development to continue on the existing Perfmon2 for the users,  
> vendors and tool authors, as well as giving you the flexibility to  
> make whatever changes you need for the LKML folks. When the interface  
> does settle, we can all work together to rolling forward our support  
> into whatever the kernel provides.
> 
> Comments?
> 
> Phil

Hi Phil,

Having two branches won't work so well with the model of development used for 
Fedora and Red Hat Enterprise Linux. Both of these distributions have the 
expectations that things are in upstream software. In some cases there may 
backport a specific feature. Neither Fedora or Red Hat Enterprise Linux are 
going to start putting the perfmon bits in until they start getting in upstream 
kernels.

The chance for divergence between the two branches is significant as patches are 
revised to be accepted into the upstream kernel. Working on the stable kernel 
platform may divert attention getting the perfmon support where it really should 
be, in the mainline kernel.

-Will