Re: Scaling noise

Nick Piggin
2003-09-04T03:42:48Z

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?