cvs commit: src/sys/vm vm_map.c vm_map.h

[Stephan Uphoff]

John Baldwin wrote:
> On Monday 02 August 2004 10:58 pm, Stephan Uphoff wrote:
> > John Baldwin wrote:
> > > On Friday 30 July 2004 12:06 pm, Brian Fundakowski Feldman wrote:
> > > > On Fri, Jul 30, 2004 at 09:10:28AM +0000, Maxime Henrion wrote:
> > > > > mux         2004-07-30 09:10:28 UTC
> > > > >
> > > > >   FreeBSD src repository
> > > > >
> > > > >   Modified files:
> > > > >     sys/vm               vm_map.c vm_map.h
> > > > >   Log:
> > > > >   Get rid of another lockmgr(9) consumer by using sx locks for the
> > > > > user maps.  We always acquire the sx lock exclusively here, but we
> > > > > can't use a mutex because we want to be able to sleep while holding
> > > > > the lock.  This is completely equivalent to what we were doing with
> > > > > the lockmgr(9) locks before.
> > > >
> > > > Not that I don't think it's worth doing in general, but is there a
> > > > comparison anyone has done between speeds of sx and lockmgr?
> > >
> > > Speed aside, when allproc_lock and proctree_lock were lockmgr locks
> > > (before sx was implemented), my SMP machines routinely locked up and when
> > > I looked at things in the debugger it seemed that no one held
> > > allproc_lock but several processes were blocked on it.  Quite frankly, I
> > > don't trust lockmgr()'s implementation.
> >
> > Since the vfs layer forces me to use the lockmgr you scared me into
> > taking a look.
> > And yes there is a bug in the current implementation. (kern/69934).
> 
> Good catch!  Unfortunately, the problems I was seeing above involved locks 
> that didn't use upgrade or downgrade. :(  

Mhhh .. I found another bug (kern/69964).
Getting closer?  ;-)

> I've pondered taking an axe to all 
> of lockmgr and just rewriting it from scratch to use mutexes and cv's like 
> sx.

I hope to take the axe on the current vfs layer. 
(Eliminating the need for lockmgr)
However it might take a while until I can show/share results.

	Stephan