Re: [PATCH v3 3/3] tools: introduce parameter max_wp_ram_ranges.

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
[snip]
> >> >> I'm getting the impression that we're moving in circles. A blanket
> >> >> limit above the 256 one for all domains is _not_ going to be
> >> >> acceptable; going to 8k will still need host admin consent. With
> >> >> your rangeset performance improvement patch, each range is
> >> >> going to be tracked by a 40 byte structure (up from 32), which
> >> >> already means an overhead increase for all the other ranges. 8k
> >> >> of wp ranges implies an overhead beyond 448k (including the
> >> >> xmalloc() overhead), which is not _that_ much, but also not
> >> >> negligible.
> >> >>
> >> >
> >> > ... which means we are still going to need a toolstack parameter to set
> the
> >> > limit. We already have a parameter for VRAM size so is having a
> parameter
> >> for
> >> > max. GTT shadow ranges such a bad thing?
> >>
> >> It's workable, but not nice (see also Ian's earlier response).
> >>
> >> > Is the fact that the memory comes
> >> > from xenheap rather than domheap the real problem?
> >>
> >> Not the primary one, since except on huge memory machines
> >> both heaps are identical. To me the primary one is the quite
> >> more significant resource consumption in the first place (I'm not
> >> going to repeat what I've written in already way too many
> >> replies before).
> >
> > Ok. Well the only way round tracking specific ranges for emulation (and
> > consequently suffering the overhead) is tracking by type. For XenGT I
> guess
> > it would be possible to live with a situation where a single ioreq server can
> > register all wp mem emulations for a given VM. I can't say I particularly
> > like that way of doing things but if it's the only way forward then I guess
> > we may have to live with it.
> 
> Well, subject to Ian not objecting (still awaiting some follow-up by
> him), I didn't mean to say doing it the proposed way is a no-go.
> All that I really insist on is that this larger resource consumption
> won't go without some form of host admin consent.
> 

Would you be ok with purely host admin consent e.g. just setting the limit via boot command line?

  Paul

> Jan