From 6e840c55cf077c166740a837edd92b8346be2cb9 Mon Sep 17 00:00:00 2001
From: Fam Zheng <famz@redhat.com>
Date: Fri, 8 Aug 2014 03:23:27 +0200
Subject: [PATCH 10/10] memory: Don't call memory_region_update_coalesced_range if nothing changed

Message-id: <1407468207-28928-1-git-send-email-famz@redhat.com>
Patchwork-id: 60486
O-Subject: [RHEL-7.0.z qemu-kvm PATCH] memory: Don't call memory_region_update_coalesced_range if nothing changed
Bugzilla: 1124660
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Amos Kong <akong@redhat.com>

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1124660
Brew: http://brewweb.devel.redhat.com/brew/taskinfo?taskID=7805797

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>
(cherry picked from commit ab5b3db5d711b290d63e954dc64647dd51cef962)
Signed-off-by: Fam Zheng <famz@redhat.com>
---
 memory.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 memory.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/memory.c b/memory.c
index edaf6fd..a71d096 100644
--- a/memory.c
+++ b/memory.c
@@ -1210,6 +1210,7 @@ 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;
@@ -1218,8 +1219,12 @@ 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)
-- 
1.7.1