On Mon, 2021-06-07 at 15:02 +1000, David Gibson wrote: > On Fri, Apr 30, 2021 at 11:36:06AM -0300, Leonardo Bras wrote: > > Because hypervisors may need to create HPTs without knowing the > > guest > > page size, the smallest used page-size (4k) may be chosen, > > resulting in > > a HPT that is possibly bigger than needed. > > > > On a guest with bigger page-sizes, the amount of entries for HTP > > may be > > too high, causing the guest to ask for a HPT resize-down on the > > first > > hotplug. > > > > This becomes a problem when HPT resize-down fails, and causes the > > HPT resize to be performed on every LMB added, until HPT size is > > compatible to guest memory size, causing a major slowdown. > > > > So, avoiding HPT resizing-down on hot-add significantly improves > > memory > > hotplug times. > > > > As an example, hotplugging 256GB on a 129GB guest took 710s without > > this > > patch, and 21s after applied. > > > > Signed-off-by: Leonardo Bras <leobra...@gmail.com> > > Sorry it's taken me so long to look at these > > I don't love the extra statefulness that the 'shrinking' parameter > adds, but I can't see an elegant way to avoid it, so: > > Reviewed-by: David Gibson <da...@gibson.dropbear.id.au>
np, thanks for reviewing! Best regards, Leonardo Bras
