Re: pgo_get()? what's that? (was Re: Device page)

[David Young <dyoung%pobox.com@localhost>]

On Mon, Feb 08, 2010 at 12:37:44AM +0900, Masao Uebayashi wrote:
> > What's pgo_get()?  Since you seem to be immersed in UVM, you may be in a
> > good position to write the manual pages that it so badly lacks.  Even if
> > you just jot some notes on each function, I can write the manual pages.
> 
> UVM abstracts things that is mapped & put onto the main memory as 
> "uvm_object".
> Most typically vnode.  UVM doesn't know how those instances corresponds to
> their backends.  When UVM wants to load those objects put onto memory, UVM
> asks its super class to get objects from backends.  That's the pgo_get()
> operation.

Do you mean subclass?

> I'm not sure it should be documented in 9 section manual.  Its interface is
> internal to VM, and somewhat ambiguous.  I'm thinking to collect pgo_* call
> sites into one place (probably uvm_object.c) and slowly rethink / improve
> the API...

I suppose that they could be internal in principle, but they are not
internal in practice. :-) For example, whenever I have looked at tmpfs,
I have found it uses undocumented uvm(9) functions *and* uvm_pagerops
calls.

Dave

-- 
David Young             OJC Technologies
dyoung%ojctech.com@localhost      Urbana, IL * (217) 278-3933