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authorXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>2013-06-19 17:09:21 +0800
committerGleb Natapov <gleb@redhat.com>2013-06-27 14:20:43 +0300
commit0cbf8e437b60b8b12d97589509d3e5a581731d36 (patch)
tree9990c3958c06c8737d19f510f90ee453c2b14350 /Documentation/virtual
parentaccaefe07ddbeb12c0de4cec1d62dba6a0ea1605 (diff)
KVM: MMU: document write_flooding_count
Document write_flooding_count to Documentation/virtual/kvm/mmu.txt Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/kvm/mmu.txt9
1 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt
index f514a3fad9b..0db7743c55e 100644
--- a/Documentation/virtual/kvm/mmu.txt
+++ b/Documentation/virtual/kvm/mmu.txt
@@ -215,6 +215,15 @@ Shadow pages contain the following information:
atomically. The reader uses this while running out of the MMU lock
to detect in-progress updates and retry them until the writer has
finished the write.
+ write_flooding_count:
+ A guest may write to a page table many times, causing a lot of
+ emulations if the page needs to be write-protected (see "Synchronized
+ and unsynchronized pages" below). Leaf pages can be unsynchronized
+ so that they do not trigger frequent emulation, but this is not
+ possible for non-leafs. This field counts the number of emulations
+ since the last time the page table was actually used; if emulation
+ is triggered too frequently on this page, KVM will unmap the page
+ to avoid emulation in the future.
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