[openib-general] [PATCH] use mmiowb after doorbell ring

[Michael S. Tsirkin]

Quoting r. Jason Gunthorpe <jgunthorpe at obsidianresearch.com>:
> Subject: Re: [PATCH] use mmiowb after doorbell ring
> 
> On Tue, Oct 17, 2006 at 08:44:34PM -0700, Roland Dreier wrote:
> >     Jason> I think the typical way this is done would be to use
> >     Jason> ld.so's 'hwcap' handling and stick an optimized library in
> >     Jason> /usr/lib/sse2.
>  
> > It's a good suggestion, but the problem is that the CPU-dependent code
> > is in the mthca.so driver-dependent plugin, which libibverbs dlopen()s
> > at runtime.  Do you know how to use the hwcap stuff with dlopen()?
> > I'm not thrilled about creating an sse2 special case in libibverbs
> > just to handle libmthca on i386.
> 
> It is automatic, I just doubled checked to be sure:

The difference here is that libibverbs insists on putting all plugins
in a separate directory and passing full path to dlopen, which of course
breaks this.

Roland, I've been looking at changing the way we handle plugins
and this might be a good reason to finally do this before 1.1:
rather than look for plugins in a pre-configured path, let's just have
a config file (or files) and ask users to put the list of plugins there.

As it is, it is already painful to keep both 32 and 64 bit libibverbs on the
same system - we have to invent a methodology for where to put 64/32 bit
libraries. And when I have to keep several library versions around for testing
it's much easier (at least, for me) to just use LD_LIBRARY_PATH for everything
and stick each version in a separate directory, than to remember playing with
special environment that was invented just for libibverbs.

Does this make sense?

-- 
MST