On 21/09/17 23:57, Paolo Bonzini wrote:
> 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.
I see, after some debugging only MRs with @terminates==true appear in the
dispatch tree which makes sense. But I am still struggling to understand
what @terminates really means here in plain english.
--
Alexey
