On Fri, 2018-06-15 at 18:09 +0300, Michael S. Tsirkin wrote:
> On Mon, Jun 11, 2018 at 11:18:57AM -0400, nilal@xxxxxxxxxx wrote:
> > From: Nitesh Narayan Lal <nilal@xxxxxxxxxx>
> > + write_seqlock(&guest_page_lock);
> > + while (idx < MAX_FGPT_ENTRIES) {
> > + unsigned long pfn = free_page_obj[idx].pfn;
> > + unsigned long pfn_end = free_page_obj[idx].pfn +
> > + free_page_obj[idx].pages -
> > 1;
> > + bool prev_free = false;
> > +
> > + while (pfn <= pfn_end) {
>
> It seems like this can be MAX_FGPT_ENTRIES^2 so 1000000 cycles in the
> inner-most loop in the worst case, all with interrupts disabled and
> all
> kind of MM locks held. This kind of latency likely won't be
> acceptable
> to the MM crowd even if it only happens once in a while.
That makes me wonder if instead of spending time making
this code perfect, it would make time to also implement
a prototype of your bitmap page hinting idea, and compare
the two.
This project is probably at the "50% effort" stage, and
the bitmap page hinting approach seems like an interesting
possible different tradeoff...
--
All Rights Reversed.Attachment:
signature.asc
Description: This is a digitally signed message part
