[dm-devel] [PATCH 3/6] libmultipath: remove code duplication in path counting

[Benjamin Marzinski]

On Thu, Aug 06, 2020 at 10:48:12AM +0000, Martin Wilck wrote:
> On Mon, 2020-07-27 at 14:24 -0500, Benjamin Marzinski wrote:
> > pathcountgr() is never used except by pathcount(), and neither is the
> > special case for PATH_WILD. Simplify this and make one function that
> > is
> > used by both pathcount() and count_active_paths(). This will be used
> > again in a future patch.
> > 
> > Also use count_active_paths() in mpath_persist.
> 
> The patch looks correct. I had thought about something like it as well
> when I first introduced count_active_paths(). But count_active_paths()
> is used a *lot*, and often in critical situations. I wonder whether it
> deserves an optimized version. The compiler can surely optimize better
> with two constant expressions than with the additional for-loop over an
> array with variable size. That's why back then I decided against
> implementing it as a special case of a generic function. I actually
> considered inlining count_active_paths().
> 
> It's hard to quantify the effect, and I haven't done any benchmarks. 
> But still, can we perhaps keep the optimized version of
> count_active_paths() itself?

Sure.

-Ben

> 
> Martin
>