On 21/09/2017 15:39, Alexey Kardashevskiy wrote:
> 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?
Yes, children override the parent. But more important, !mr->terminates
means that patch 3 doesn't think that MR produces an empty FlatView.
>
>> + 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.
Yeah, I did take some inspiration from your code, but we were thinking
of different scenarios (I wanted to cover the child->enabled == true).
Paolo
>
>> + /* 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;
>>
>
>
