From ab5b3db5d711b290d63e954dc64647dd51cef962 Mon Sep 17 00:00:00 2001 From: Fam Zheng 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 Signed-off-by: Paolo Bonzini --- memory.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/memory.c b/memory.c index 85798b0..4895e25 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) -- 2.7.4