Re: [PATCH 2/3] KVM: Guest page hinting functionality

[Rik van Riel <riel@redhat.com>]

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On Wed, 2017-08-02 at 14:59 -0400, Nitesh Narayan Lal wrote:
> 
> > > -struct hypervisor_pages hypervisor_pagelist[MAX_FGPT_ENTRIES];
> > > +struct hypervisor_pages hypervisor_pagelist[MAX_FGPT_ENTRIES -
> > > 1];
> > > +
> > > +static void empty_hyperlist(void)
> > > +{
> > > +	int i = 0;
> > > +
> > > +	while (i < MAX_FGPT_ENTRIES - 1) {
> > 
> >       MAX_FGPT_ENTRIES in-place of 'MAX_FGPT_ENTRIES - 1' here
> >       and at similar other places?
> 
> This is because CPU local list has a total of 1000 entries
> (MAX_FGPT_ENTRIES) where as CPU global list has 999 entries. If you
> see
> the arch_free_page_slowpath() and consider a situation where there
> are
> 1000 entries of singly allocated free pages in cpu-local list i.e.,
> none
> of them are re-allocated. While adding them to the cpu global list
> when
> cpu local list index reaches to 1000 the outer loop will terminate
> due
> to which cpu global list index will never reach to 1000 and
> compress_hyperlist()/make_hypercall() will never be called.
> > 
> 
Can you explain why the hypervisor_pagelist
is smaller than the cpu local list?

This makes no sense to me. Why are they not
the same size?

That would certainly make the code easier to read.

-- 
All rights reversed

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