commit dfd34be42b559a7caf607b9dca771432cf28491e
author Sandeep Patil <sspatil@google.com> Sun Jan 13 17:39:08 2019 -0800
committer Sandeep Patil <sspatil@google.com> Mon Jan 14 09:43:32 2019 -0800
tree 19b1ae3a07fc9ddcc143f7a9b19f9b724076c3f0
parent 8871e7e90f393bce69608ea19112aa15e4914166

meminfo: Add IsSmapsRollupSupported Api

Consolidate the checking of /proc/<pid>/smaps_rollup support
in libmeminfo and do it in a thread safe way.

Use the API in ProcMemInfo as well to eliminate the extra
parameters passed to SmapsOrRollup* methods.

Bug: 111694435
Test: libmeminfo_test 1 --gtest_filter=TestProcMemInfo.IsSmapsSupportedTest
Test: Tested with and without the smaps_rollup support in kernel.

Change-Id: I992057f06b54569025fa0cdade9618da2675d1de
Merged-In: I992057f06b54569025fa0cdade9618da2675d1de
Signed-off-by: Sandeep Patil <sspatil@google.com>

libmeminfo/procmeminfo.cpp

diff --git a/libmeminfo/procmeminfo.cpp b/libmeminfo/procmeminfo.cpp
index f72d469..347a293 100644
--- a/libmeminfo/procmeminfo.cpp
+++ b/libmeminfo/procmeminfo.cpp
@@ -21,6 +21,7 @@
 #include <stdio.h>
 #include <unistd.h>
 
+#include <atomic>
 #include <fstream>
 #include <iostream>
 #include <memory>
@@ -172,15 +173,15 @@
     return ForEachVmaFromFile(path, callback);
 }
 
-bool ProcMemInfo::SmapsOrRollup(bool use_rollup, MemUsage* stats) const {
-    std::string path = ::android::base::StringPrintf("/proc/%d/%s", pid_,
-                                                     use_rollup ? "smaps_rollup" : "smaps");
+bool ProcMemInfo::SmapsOrRollup(MemUsage* stats) const {
+    std::string path = ::android::base::StringPrintf(
+            "/proc/%d/%s", pid_, IsSmapsRollupSupported(pid_) ? "smaps_rollup" : "smaps");
     return SmapsOrRollupFromFile(path, stats);
-};
+}
 
-bool ProcMemInfo::SmapsOrRollupPss(bool use_rollup, uint64_t* pss) const {
-    std::string path = ::android::base::StringPrintf("/proc/%d/%s", pid_,
-                                                     use_rollup ? "smaps_rollup" : "smaps");
+bool ProcMemInfo::SmapsOrRollupPss(uint64_t* pss) const {
+    std::string path = ::android::base::StringPrintf(
+            "/proc/%d/%s", pid_, IsSmapsRollupSupported(pid_) ? "smaps_rollup" : "smaps");
     return SmapsOrRollupPssFromFile(path, pss);
 }
 
@@ -374,6 +375,31 @@
     return true;
 }
 
+enum smaps_rollup_support { UNTRIED, SUPPORTED, UNSUPPORTED };
+
+static std::atomic<smaps_rollup_support> g_rollup_support = UNTRIED;
+
+bool IsSmapsRollupSupported(pid_t pid) {
+    // Similar to OpenSmapsOrRollup checks from android_os_Debug.cpp, except
+    // the method only checks if rollup is supported and returns the status
+    // right away.
+    enum smaps_rollup_support rollup_support = g_rollup_support.load(std::memory_order_relaxed);
+    if (rollup_support != UNTRIED) {
+        return rollup_support == SUPPORTED;
+    }
+    std::string rollup_file = ::android::base::StringPrintf("/proc/%d/smaps_rollup", pid);
+    if (access(rollup_file.c_str(), F_OK | R_OK)) {
+        // No check for errno = ENOENT necessary here. The caller MUST fallback to
+        // using /proc/<pid>/smaps instead anyway.
+        g_rollup_support.store(UNSUPPORTED, std::memory_order_relaxed);
+        return false;
+    }
+
+    g_rollup_support.store(SUPPORTED, std::memory_order_relaxed);
+    LOG(INFO) << "Using smaps_rollup for pss collection";
+    return true;
+}
+
 bool SmapsOrRollupFromFile(const std::string& path, MemUsage* stats) {
     auto fp = std::unique_ptr<FILE, decltype(&fclose)>{fopen(path.c_str(), "re"), fclose};
     if (fp == nullptr) {