[GitHub] [nifi-minifi-cpp] adam-markovics commented on a change in pull request #845: MINIFICPP-1277 - Create cross-platform API for querying memory usage

[GitBox <gi...@apache.org>]

adam-markovics commented on a change in pull request #845:
URL: https://github.com/apache/nifi-minifi-cpp/pull/845#discussion_r458809881



##########
File path: libminifi/include/utils/OsUtils.h
##########
@@ -31,6 +31,12 @@ namespace OsUtils {
  */
 extern std::string userIdToUsername(const std::string &uid);
 
+/**
+ * Returns memory usage in bytes
+ */
+
+unsigned long long getMemoryUsage();

Review comment:
       Done.

##########
File path: libminifi/src/utils/OsUtils.cpp
##########
@@ -154,6 +160,80 @@ std::string OsUtils::userIdToUsername(const std::string &uid) {
   return name;
 }
 
+unsigned long long OsUtils::getMemoryUsage() {
+#ifdef __linux__
+  long resPages;
+  long sharedPages;
+  {
+    std::string ignore;
+    std::ifstream ifs("/proc/self/statm");
+    ifs >> ignore >> resPages >> sharedPages;
+  }
+
+  if (sharedPages > resPages) {
+    throw std::range_error("Shared memory page count ("
+      + std::to_string(sharedPages)
+      + ") should not be larger than resident set size ("
+      + std::to_string(resPages)
+      + "), that includes it"
+    );
+  }
+
+  const long ownPages = resPages - sharedPages;

Review comment:
       This code is Linux-only. Man says values in /proc/self/statm will be long: https://man7.org/linux/man-pages/man5/proc.5.html. Page size is usually 4096, memory usage value should definitely fit 64 bytes even after multiplication.




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