[ofa-general] Re: Re: [PATCH RFC] sharing userspace IB objects

[Michael S. Tsirkin]

> Quoting Gleb Natapov <glebn at voltaire.com>:
> Subject: Re: Re: [PATCH RFC] sharing userspace IB objects
> 
> On Tue, Jun 26, 2007 at 03:58:02PM +0300, Michael S. Tsirkin wrote:
> > > > No, sharing a send queue must be done in software.  I don't really see the reason
> > > > for sarcasm: do you see value in sharing resources between multiple threads?
> > > > Why not multiple processes? Some people just don't want to program
> > > > in multithreaded environment.
> > >
> > > Yes I see the value in sharing resources between threads and processes
> > > if done right. This proposition is far from being right.
> > 
> > Ahem, *what* are you talking about? Sharing resources between threads was supported in
> > libibverbs 1.0, *right from the start*. This is still the case with 1.1, and this API
> > matches verbs quite closely which means that it can work pretty much on any
> > hardware.
> 
> Why do you think that I have a problem with multithreaded application is
> beyond my understanding. I have a problem with you thinking that peaking a
> completion by random process in FCFS order is a good idea.

Should that have been "picking"?  I keep telling you. With multithreaded
applications *that's what currently happens*. If multiple threads poll a CQ,
which one gets which completion is currently unspecified. Are you
worried about this? If not, why are you worried when multiple
processes do this?

Look here, hardware features do *not* just materialize when you build an API for
them.  What good would a pretty API that no hardware supports be?  It's the
other way around: I'm trying to extend our API to improve scalability with
existing hardware.

-- 
MST