Reduce statsd log data size.
1. Hash the strings in metric dimensions.
2. Optimize the timestamp encoding in bucket.
Use bucket num for full bucket and millis for
partial bucket.
3. Encode the dimension path per metric and avoid
deduping it across dimensons.
Test: statsd test
Change-Id: I18f69654de85edb21a9c835c73edead756295e05
BUG: b/77813755
diff --git a/cmds/statsd/src/hash.cpp b/cmds/statsd/src/hash.cpp
new file mode 100644
index 0000000..c501c9f
--- /dev/null
+++ b/cmds/statsd/src/hash.cpp
@@ -0,0 +1,130 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "hash.h"
+
+namespace android {
+namespace os {
+namespace statsd {
+
+namespace {
+// Lower-level versions of Get... that read directly from a character buffer
+// without any bounds checking.
+inline uint32_t DecodeFixed32(const char *ptr) {
+ return ((static_cast<uint32_t>(static_cast<unsigned char>(ptr[0]))) |
+ (static_cast<uint32_t>(static_cast<unsigned char>(ptr[1])) << 8) |
+ (static_cast<uint32_t>(static_cast<unsigned char>(ptr[2])) << 16) |
+ (static_cast<uint32_t>(static_cast<unsigned char>(ptr[3])) << 24));
+}
+
+inline uint64_t DecodeFixed64(const char* ptr) {
+ uint64_t lo = DecodeFixed32(ptr);
+ uint64_t hi = DecodeFixed32(ptr + 4);
+ return (hi << 32) | lo;
+}
+
+// 0xff is in case char is signed.
+static inline uint32_t ByteAs32(char c) { return static_cast<uint32_t>(c) & 0xff; }
+static inline uint64_t ByteAs64(char c) { return static_cast<uint64_t>(c) & 0xff; }
+
+} // namespace
+
+uint32_t Hash32(const char *data, size_t n, uint32_t seed) {
+ // 'm' and 'r' are mixing constants generated offline.
+ // They're not really 'magic', they just happen to work well.
+ const uint32_t m = 0x5bd1e995;
+ const int r = 24;
+
+ // Initialize the hash to a 'random' value
+ uint32_t h = static_cast<uint32_t>(seed ^ n);
+
+ // Mix 4 bytes at a time into the hash
+ while (n >= 4) {
+ uint32_t k = DecodeFixed32(data);
+ k *= m;
+ k ^= k >> r;
+ k *= m;
+ h *= m;
+ h ^= k;
+ data += 4;
+ n -= 4;
+ }
+
+ // Handle the last few bytes of the input array
+ switch (n) {
+ case 3:
+ h ^= ByteAs32(data[2]) << 16;
+ case 2:
+ h ^= ByteAs32(data[1]) << 8;
+ case 1:
+ h ^= ByteAs32(data[0]);
+ h *= m;
+ }
+
+ // Do a few final mixes of the hash to ensure the last few
+ // bytes are well-incorporated.
+ h ^= h >> 13;
+ h *= m;
+ h ^= h >> 15;
+ return h;
+}
+
+uint64_t Hash64(const char* data, size_t n, uint64_t seed) {
+ const uint64_t m = 0xc6a4a7935bd1e995;
+ const int r = 47;
+
+ uint64_t h = seed ^ (n * m);
+
+ while (n >= 8) {
+ uint64_t k = DecodeFixed64(data);
+ data += 8;
+ n -= 8;
+
+ k *= m;
+ k ^= k >> r;
+ k *= m;
+
+ h ^= k;
+ h *= m;
+ }
+
+ switch (n) {
+ case 7:
+ h ^= ByteAs64(data[6]) << 48;
+ case 6:
+ h ^= ByteAs64(data[5]) << 40;
+ case 5:
+ h ^= ByteAs64(data[4]) << 32;
+ case 4:
+ h ^= ByteAs64(data[3]) << 24;
+ case 3:
+ h ^= ByteAs64(data[2]) << 16;
+ case 2:
+ h ^= ByteAs64(data[1]) << 8;
+ case 1:
+ h ^= ByteAs64(data[0]);
+ h *= m;
+ }
+
+ h ^= h >> r;
+ h *= m;
+ h ^= h >> r;
+
+ return h;
+}
+} // namespace statsd
+} // namespace os
+} // namespace android