From: Longpeng <longpe...@huawei.com>
When updating ioeventfds, we need to iterate all address spaces and
iterate all flat ranges of each address space. There is so much
redundant process that a FlatView would be iterated for so many times
during one commit (memory_region_transaction_commit).
We can mark a FlatView as UPDATED and then skip it in the next iteration
and clear the UPDATED flag at the end of the commit. The overhead can
be significantly reduced.
For example, a VM with 16 vdpa net devices and each one has 65 vectors,
can reduce the time spent on memory_region_transaction_commit by 95%.
Signed-off-by: Longpeng <longpe...@huawei.com>
---
include/exec/memory.h | 2 ++
softmmu/memory.c | 28 +++++++++++++++++++++++++++-
2 files changed, 29 insertions(+), 1 deletion(-)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 2e602a2fad..974eabf765 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -1093,6 +1093,8 @@ struct FlatView {
unsigned nr_allocated;
struct AddressSpaceDispatch *dispatch;
MemoryRegion *root;
+#define FLATVIEW_FLAG_IOEVENTFD_UPDATED (1 << 0)
+ unsigned flags;
};
static inline FlatView *address_space_to_flatview(AddressSpace *as)
diff --git a/softmmu/memory.c b/softmmu/memory.c
index 9d64efca26..71ff996712 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -815,6 +815,15 @@ FlatView *address_space_get_flatview(AddressSpace *as)
return view;
}
+static void address_space_reset_view_flags(AddressSpace *as, unsigned mask)
+{
+ FlatView *view = address_space_get_flatview(as);
+
+ if (view->flags & mask) {
+ view->flags &= ~mask;
+ }
+}
+
static void address_space_update_ioeventfds(AddressSpace *as)
{
FlatView *view;
@@ -825,6 +834,12 @@ static void address_space_update_ioeventfds(AddressSpace
*as)
AddrRange tmp;
unsigned i;
+ view = address_space_get_flatview(as);
+ if (view->flags & FLATVIEW_FLAG_IOEVENTFD_UPDATED) {
+ return;
+ }
+ view->flags |= FLATVIEW_FLAG_IOEVENTFD_UPDATED;
+
/*
* It is likely that the number of ioeventfds hasn't changed much, so use
* the previous size as the starting value, with some headroom to avoid
@@ -833,7 +848,6 @@ static void address_space_update_ioeventfds(AddressSpace
*as)
ioeventfd_max = QEMU_ALIGN_UP(as->ioeventfd_nb, 4);
ioeventfds = g_new(MemoryRegionIoeventfd, ioeventfd_max);
- view = address_space_get_flatview(as);
FOR_EACH_FLAT_RANGE(fr, view) {
for (i = 0; i < fr->mr->ioeventfd_nb; ++i) {
tmp = addrrange_shift(fr->mr->ioeventfds[i].addr,
@@ -1086,6 +1100,15 @@ void memory_region_transaction_begin(void)
++memory_region_transaction_depth;
}
+static inline void address_space_update_ioeventfds_finish(void)
+{
+ AddressSpace *as;
+
+ QTAILQ_FOREACH(as, &address_spaces, address_spaces_link) {
+ address_space_reset_view_flags(as, FLATVIEW_FLAG_IOEVENTFD_UPDATED);
+ }
+}
+
void memory_region_transaction_commit(void)
{
AddressSpace *as;
@@ -1106,12 +1129,14 @@ void memory_region_transaction_commit(void)
}
memory_region_update_pending = false;
ioeventfd_update_pending = false;
+ address_space_update_ioeventfds_finish();
MEMORY_LISTENER_CALL_GLOBAL(commit, Forward);
} else if (ioeventfd_update_pending) {
QTAILQ_FOREACH(as, &address_spaces, address_spaces_link) {
address_space_update_ioeventfds(as);
}
ioeventfd_update_pending = false;
+ address_space_update_ioeventfds_finish();
}
}
}
@@ -3076,6 +3101,7 @@ void address_space_init(AddressSpace *as, MemoryRegion
*root, const char *name)
as->name = g_strdup(name ? name : "anonymous");
address_space_update_topology(as);
address_space_update_ioeventfds(as);
+ address_space_reset_view_flags(as, FLATVIEW_FLAG_IOEVENTFD_UPDATED);
}
static void do_address_space_destroy(AddressSpace *as)
--
2.23.0
