95d4c16ce7
Currently, write protecting a slot needs to walk all the shadow pages and checks ones which have a pte mapping a page in it. The walk is overly heavy when dirty pages in that slot are not so many and checking the shadow pages would result in unwanted cache pollution. To mitigate this problem, we use rmap_write_protect() and check only the sptes which can be reached from gfns marked in the dirty bitmap when the number of dirty pages are less than that of shadow pages. This criterion is reasonable in its meaning and worked well in our test: write protection became some times faster than before when the ratio of dirty pages are low and was not worse even when the ratio was near the criterion. Note that the locking for this write protection becomes fine grained. The reason why this is safe is descripted in the comments. Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp> Signed-off-by: Avi Kivity <avi@redhat.com> |
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