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memory: avoid updating ioeventfds for some address_space

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When updating ioeventfds, we need to iterate all address spaces,
but some address spaces do not register eventfd_add|del call when
memory_listener_register() and they do nothing when updating ioeventfds.
So we can skip these AS in address_space_update_ioeventfds().

The overhead of memory_region_transaction_commit() can be significantly
reduced. For example, a VM with 8 vhost net devices and each one has
64 vectors, can reduce the time spent on memory_region_transaction_commit by 20%.

Message-ID: <20230830032906.12488-1-hongmianquan@bytedance.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: hongmianquan <hongmianquan@bytedance.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
This commit is contained in:
hongmianquan
2023-08-30 11:29:06 +08:00
committed by David Hildenbrand
parent 41ddcd2308
commit 544cff46c0
2 changed files with 13 additions and 0 deletions
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include/exec/memory.h
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@@ -1095,6 +1095,7 @@ struct AddressSpace {
struct FlatView *current_map;
int ioeventfd_nb;
int ioeventfd_notifiers;
struct MemoryRegionIoeventfd *ioeventfds;
QTAILQ_HEAD(, MemoryListener) listeners;
QTAILQ_ENTRY(AddressSpace) address_spaces_link;