libmeminfo: Add libmeminfo to gather global and per-process memory stats

The library is expected to be a unified place for all components to read
both global and per-process memory accounting form kernel including
getting the working set. This change adds the PageInfo, MemInfo and
ProcMemInfo classes and verifies the implementation against libpagemap
for correctness.

Adds a procmem2 tool show the usage.

TODO: Plumbing in os_debug, add vmastats, zoneinfo etc parsing.

Test: libmeminfo_test 1
Test: procmem2 1
Test: procmem2 -h -W 1
Test: procmem2 -h -w 1
Test: libmeminfo_benchmark
Bug: 111694435
Bug: 114325007

Change-Id: I280440b1dc26a498170686d10fcf63f953a0dcbd
Signed-off-by: Sandeep Patil <sspatil@google.com>
diff --git a/libmeminfo/sysmeminfo.cpp b/libmeminfo/sysmeminfo.cpp
new file mode 100644
index 0000000..50fa213
--- /dev/null
+++ b/libmeminfo/sysmeminfo.cpp
@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2018 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 <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <cctype>
+#include <fstream>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/parseint.h>
+#include <android-base/strings.h>
+
+#include "meminfo_private.h"
+
+namespace android {
+namespace meminfo {
+
+const std::vector<std::string> SysMemInfo::kDefaultSysMemInfoTags = {
+    "MemTotal:", "MemFree:",      "Buffers:",     "Cached:",     "Shmem:",
+    "Slab:",     "SReclaimable:", "SUnreclaim:",  "SwapTotal:",  "SwapFree:",
+    "ZRam:",     "Mapped:",       "VmallocUsed:", "PageTables:", "KernelStack:",
+};
+
+bool SysMemInfo::ReadMemInfo(const std::string& path) {
+    return ReadMemInfo(SysMemInfo::kDefaultSysMemInfoTags, path);
+}
+
+// TODO: Delete this function if it can't match up with the c-like implementation below.
+// Currently, this added about 50 % extra overhead on hikey.
+#if 0
+bool SysMemInfo::ReadMemInfo(const std::vector<std::string>& tags, const std::string& path) {
+    std::string buffer;
+    if (!::android::base::ReadFileToString(path, &buffer)) {
+        PLOG(ERROR) << "Failed to read : " << path;
+        return false;
+    }
+
+    uint32_t total_found = 0;
+    for (auto s = buffer.begin(); s < buffer.end() && total_found < tags.size();) {
+        for (auto& tag : tags) {
+            if (tag == std::string(s, s + tag.size())) {
+                s += tag.size();
+                while (isspace(*s)) s++;
+                auto num_start = s;
+                while (std::isdigit(*s)) s++;
+
+                std::string number(num_start, num_start + (s - num_start));
+                if (!::android::base::ParseUint(number, &mem_in_kb_[tag])) {
+                    LOG(ERROR) << "Failed to parse uint";
+                    return false;
+                }
+                total_found++;
+                break;
+            }
+        }
+        while (s < buffer.end() && *s != '\n') s++;
+        if (s < buffer.end()) s++;
+    }
+
+    return true;
+}
+
+#else
+bool SysMemInfo::ReadMemInfo(const std::vector<std::string>& tags, const std::string& path) {
+    char buffer[4096];
+    int fd = open(path.c_str(), O_RDONLY | O_CLOEXEC);
+    if (fd < 0) {
+        PLOG(ERROR) << "Failed to open file :" << path;
+        return false;
+    }
+
+    const int len = read(fd, buffer, sizeof(buffer) - 1);
+    close(fd);
+    if (len < 0) {
+        return false;
+    }
+
+    buffer[len] = '\0';
+    char* p = buffer;
+    uint32_t found = 0;
+    while (*p && found < tags.size()) {
+        for (auto& tag : tags) {
+            if (strncmp(p, tag.c_str(), tag.size()) == 0) {
+                p += tag.size();
+                while (*p == ' ') p++;
+                char* endptr = nullptr;
+                mem_in_kb_[tag] = strtoull(p, &endptr, 10);
+                if (p == endptr) {
+                    PLOG(ERROR) << "Failed to parse line in file: " << path;
+                    return false;
+                }
+                p = endptr;
+                found++;
+                break;
+            }
+        }
+        while (*p && *p != '\n') {
+            p++;
+        }
+        if (*p) p++;
+    }
+
+    return true;
+}
+#endif
+
+}  // namespace meminfo
+}  // namespace android