[CRIU] [PATCH 1/2] pagemap-cache: Introduce engine

[Cyrill Gorcunov]

On Mon, Feb 17, 2014 at 11:14:10PM +0400, Pavel Emelyanov wrote:
> >>> +
> >>> +		list_for_each_entry_continue(vma, pmc->vma_head, list) {
> >>> +			if (vma->e->start > high || vma->e->end > high)
> >>> +				break;
> >>> +
> >>
> >> So, we just merge the next vma regardless of how far from the previous it is.
> >> Why?
> > 
> > We pick next only if previous VMA is less than 2M and lays close to low 2M
> > bound, then next VMA is tested to have both addresses inside high 2M bound.
> 
> Why don't we check the size of the gap between the 1st and the 2nd (and all
> subsequent) vmas?

Because it's easier. We don't have to track "previous" vmas and such. What we
do -- we simply make sure the all "next" vmas are laying in same 2M area. As
I posted you privately the results or "reading" shows that even small VMAs
read at once by 2M chunk is still faster than doing 2 reads.