Re: Scaling noise

[Nick Piggin]

Larry McVoy wrote:

> On Wed, Sep 03, 2003 at 06:12:53PM -0700, William Lee Irwin III wrote:
>
> > On Wed, Sep 03, 2003 at 02:51:35PM -0700, William Lee Irwin III wrote:
> >
> > > > This is only truly feasible when the nodes are homogeneous. They will
> > > > not be as there will be physical locality (esp. bits like device
> > > > proximity) concerns. 
> > On Wed, Sep 03, 2003 at 05:58:22PM -0700, Larry McVoy wrote:
> >
> > > Huh?  The nodes are homogeneous.  Devices are either local or proxied.
> > Virtualized devices are backed by real devices at some level, so the
> > distance from the node's physical location to the device's then matters.
>
> Go read what I've written about this.  There is no sharing, devices are 
> local or remote.  You share in the page cache only, if you want fast access
> to a device you ask it to put the data in memory and you map it.  It's 
> absolutely as fast as an SMP.  With no locking.

There is probably more to it - I'm just an interested bystander - but
how much locking does this case incur with a single kernel system?
And what happens if more than one node wants to access the device? Through
a filesystem?


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