Re: [Xen-devel] [PATCH XEN v6 25/32] tools/libs/gnttab: Extensive updates to API documentation.

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Wed, 2015-12-09 at 16:09 +0000, Ian Jackson wrote:
> > + * The child must open a new handle if they want to interact with
> > + * gnttab.
> > Â *
> > - * Return an fd onto the grant table driver.ÂÂLogs errors.
> > + * A child may safely call xengnttab_close() on a xengnttab_handle
> > + * inherited from a parent and this will safely reclaim any virtual
> > + * address space used by mappings associated with that handle.
> 
> Is this actually true ?ÂÂNormally close() on an fd does not munmap
> anything mmapped from the fd.

Uh yes, I was talking rubbish here, unless the drivers are more magic than
I think they are.

So what is the answer? That such memory is wasted and irrecovable until
exec?

See also the discussion beneath Wei's reply.

Ack to all other feedback.

> > +ÂÂÂÂÂÂÂÂÂ* Because there are no notifications when the page is swapped
> > +ÂÂÂÂÂÂÂÂÂ* in, wait a bit before retrying, and hope that the page will
> > +ÂÂÂÂÂÂÂÂÂ* arrive eventually.
> 
> WTF.ÂÂBut not a blocker.

Quite. A feature of much of the paging code AFAICT...

> 
> 
> Ian.

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