On 21/09/17 22:07, Paolo Bonzini wrote:
> A container can be used instead of an alias to allow switching between
> multiple subregions. In this case we cannot directly share the
> subregions (since they only belong to a single parent), but if the
> subregions are aliases we can in turn walk those.
>
> While this does not reduce much the number of FlatViews that are created,
> it makes it possible to share the PCI bus master FlatViews and their
> AddressSpaceDispatch structures. For 112 virtio-net-pci devices, boot time
> is reduced from 25 to 10 seconds and memory consumption from 1.4 to 1 G.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> memory.c | 41 +++++++++++++++++++++++++++++++++++------
> 1 file changed, 35 insertions(+), 6 deletions(-)
>
> diff --git a/memory.c b/memory.c
> index 4952cc5d84..3207ae55e2 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -733,12 +733,41 @@ static void render_memory_region(FlatView *view,
>
> static MemoryRegion *memory_region_get_flatview_root(MemoryRegion *mr)
> {
> - while (mr->alias && !mr->alias_offset &&
> - int128_ge(mr->size, mr->alias->size)) {
> - /* The alias is included in its entirety. Use it as
> - * the "real" root, so that we can share more FlatViews.
> - */
> - mr = mr->alias;
> + while (mr->enabled) {
> + if (mr->alias && !mr->alias_offset &&
> + int128_ge(mr->size, mr->alias->size)) {
> + /* The alias is included in its entirety. Use it as
> + * the "real" root, so that we can share more FlatViews.
> + */
> + mr = mr->alias;
> + continue;
> + }
> +
> + if (!mr->terminates) {
Can an MR have terminates==true and children by the same time? If so, what for?
> + unsigned int found = 0;
> + MemoryRegion *child, *next = NULL;
> + QTAILQ_FOREACH(child, &mr->subregions, subregions_link) {
> + if (child->enabled) {
> + if (++found > 1) {
> + next = NULL;
> + break;
> + }
> + if (!child->addr && int128_ge(mr->size, child->size)) {
Ah, I tried this one but in v4's 18/18 (that hinting thing), did not work
out but for a different reason.
> + /* A child is included in its entirety. If it's the
> only
> + * enabled one, use it in the hope of finding an
> alias down the
> + * way. This will also let us share FlatViews.
> + */
> + next = child;
> + }
> + }
> + }
> + if (next) {
> + mr = next;
> + continue;
> + }
> + }
> +
> + break;
> }
>
> return mr;
>
--
Alexey
