RE: [PATCH v3 1/3] eal: add lcore poll busyness telemetry

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Bruce Richardson [mailto:bruce.richardson@intel.com]
> Sent: Monday, 29 August 2022 12.41
> 
> On Fri, Aug 26, 2022 at 05:46:48PM +0200, Morten Brørup wrote:
> >
> > Also, there's a new discussion about EAL bloat [1]. Perhaps I'm
> stretching it here, but it would be nice if your library was made a
> separate library, instead of part of the EAL library. (Since this kind
> of feature is not new to the EAL, I will categorize this suggestion as
> "nice to have", not "must have".)
> >
> > [1] http://inbox.dpdk.org/dev/2594603.Isy0gbHreE@thomas/T/
> >
> 
> I was actually discussing this with Kevin and Dave H. on Friay, and
> trying
> to make this a separate library is indeed a big stretch. :-)
> 
> From that discussion, the key point/gap is that we are really missing a
> clean way of providing undefs or macro fallbacks for when a library is
> just
> not present. For example, if this was a separate library we would gain
> a
> number of advantages e.g. no need for separate enable/disable flag, but
> the
> big disadvantage is that every header include for it, and every
> reference
> to the macros used in that header need to be surrounded by big ugly
> ifdefs.

I agree that we don't want everything surrounded by big ugly ifdefs.

I think solving this should be the responsibility of a library itself, not of the application or other libraries.

E.g. like the mbuf library's use of RTE_LIBRTE_MBUF_DEBUG.

Additionally, a no-op variant of the library could be required, to be compiled in when the library is disabled at build time.

> 
> For now, adding this into EAL is the far more practical approach, since
> it
> means that even if support for the feature is disabled at build time
> the
> header is still available to provide the appropriate no-op macros.

I think you already discovered the key to solving this problem, but perhaps didn't even notice it yourselves:

It must be possible to omit the *feature* at build time - not necessarily the *library*.