[Devel] Re: [RFC][PATCH 5/7] VPIDs: vpid/pid conversion in VPID enabled case

[Serge E. Hallyn]

Quoting Dave Hansen (haveblue at us.ibm.com):
> On Thu, 2006-02-02 at 19:30 +0300, Kirill Korotaev wrote:
> > This is the main patch which contains all vpid-to-pid conversions
> > and auxilliary stuff. Virtual pids are distinguished from real ones
> > by the VPID_BIT bit set. Conversion from vpid to pid and vice versa
> > is performed in two ways: fast way, when vpid and it's according pid
> > differ only in VPID_BIT bit set ("linear" case), and more complex way,
> > when pid may correspond to any vpid ("sparse" case) - in this case we
> > use a hash-table based mapping. 
> 
> This is an interesting approach.  Could you elaborate a bit on on why
> you need the two different approaches?  What conditions cause the switch
> to the sparse approach?
> 
> Also, if you could separate those two approaches out into two different
> patches, it would be much easier to get a grasp about what's going on.
> One of them is just an optimization, right?
> 
> Did you happen to catch Linus's mail about his preferred approach?  
> 
> http://marc.theaimsgroup.com/?l=linux-kernel&m=113874154731279&w=2

And in particular, is there any functionality which you could not
implement by using this approach, which you can implement with the
pid_to_vpid approach?

thanks,
-serge