Clear (madvise) card table for CC
Since the cards are not really used, we can madvise them to reduce
RAM. Image and zygote cards are cleared in pause to prevent races
between with mutators.
Pause time goes up by only 1.5us on N6P maps:
(Paused)ClearCards: Sum: 755us 99% C.I. 0.250us-28us Avg: 1.540us Max: 28us
AOSP N6P before (60s after boot system wide CC):
4,194K: .GC
4,172K: .GC
4,110K: .GC
After:
3,253K: .GC
3,205K: .GC
3,245K: .GC
Bug: 12687968
Test: test-art-host
Change-Id: I3194b5b8044c2dca427302c32d9974920fecb289
diff --git a/runtime/mem_map.cc b/runtime/mem_map.cc
index bb07fcb..e4c67e0 100644
--- a/runtime/mem_map.cc
+++ b/runtime/mem_map.cc
@@ -918,4 +918,23 @@
}
}
+void ZeroAndReleasePages(void* address, size_t length) {
+ uint8_t* const mem_begin = reinterpret_cast<uint8_t*>(address);
+ uint8_t* const mem_end = mem_begin + length;
+ uint8_t* const page_begin = AlignUp(mem_begin, kPageSize);
+ uint8_t* const page_end = AlignDown(mem_end, kPageSize);
+ if (!kMadviseZeroes || page_begin >= page_end) {
+ // No possible area to madvise.
+ std::fill(mem_begin, mem_end, 0);
+ } else {
+ // Spans one or more pages.
+ DCHECK_LE(mem_begin, page_begin);
+ DCHECK_LE(page_begin, page_end);
+ DCHECK_LE(page_end, mem_end);
+ std::fill(mem_begin, page_begin, 0);
+ CHECK_NE(madvise(page_begin, page_end - page_begin, MADV_DONTNEED), -1) << "madvise failed";
+ std::fill(page_end, mem_end, 0);
+ }
+}
+
} // namespace art