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>
This commit is contained in:
Xiao Guangrong 2013-06-19 17:09:21 +08:00 коммит произвёл Gleb Natapov
Родитель accaefe07d
Коммит 0cbf8e437b
2 изменённых файлов: 10 добавлений и 0 удалений

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@ -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.
Reverse map
===========

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@ -233,6 +233,7 @@ struct kvm_mmu_page {
int clear_spte_count;
#endif
/* Number of writes since the last time traversal visited this page. */
int write_flooding_count;
};