From ab5b3db5d711b290d63e954dc64647dd51cef962 Mon Sep 17 00:00:00 2001
From: Fam Zheng <famz@redhat.com>
Date: Fri, 13 Jun 2014 14:34:41 +0800
Subject: [PATCH] memory: Don't call memory_region_update_coalesced_range if
nothing changed
With huge number of PCI devices in the system (for example, 200
virtio-blk-pci), this unconditional call can slow down emulation of
irrelevant PCI operations drastically, such as a BAR update on a device
that has no coalescing region. So avoid it.
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
memory.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/memory.c b/memory.c
index 85798b0299..4895e25376 100644
--- a/memory.c
+++ b/memory.c
@@ -1332,6 +1332,7 @@ void memory_region_add_coalescing(MemoryRegion *mr,
void memory_region_clear_coalescing(MemoryRegion *mr)
{
CoalescedMemoryRange *cmr;
+ bool updated = false;
qemu_flush_coalesced_mmio_buffer();
mr->flush_coalesced_mmio = false;
@@ -1340,8 +1341,12 @@ void memory_region_clear_coalescing(MemoryRegion *mr)
cmr = QTAILQ_FIRST(&mr->coalesced);
QTAILQ_REMOVE(&mr->coalesced, cmr, link);
g_free(cmr);
+ updated = true;
+ }
+
+ if (updated) {
+ memory_region_update_coalesced_range(mr);
}
- memory_region_update_coalesced_range(mr);
}
void memory_region_set_flush_coalesced(MemoryRegion *mr)