diff --git a/src/ray/util/filesystem.cc b/src/ray/util/filesystem.cc
index ae961083c..4e1c119e5 100644
--- a/src/ray/util/filesystem.cc
+++ b/src/ray/util/filesystem.cc
@@ -24,49 +24,10 @@
 
 namespace ray {
 
-std::string GetExeSuffix() {
-  std::string result;
-#ifdef _WIN32
-  result = ".exe";
-#endif
-  return result;
-}
-
 std::string GetFileName(const std::string &path) {
-  size_t i = GetRootPathLength(path), j = path.size();
-  while (j > i && !IsDirSep(path[j - 1])) {
-    --j;
-  }
-  return path.substr(j);
+  return std::filesystem::path(path).filename().string();
 }
 
-size_t GetRootPathLength(const std::string &path) {
-  size_t i = 0;
-#ifdef _WIN32
-  if (i + 2 < path.size() && IsDirSep(path[i]) && IsDirSep(path[i + 1]) &&
-      !IsDirSep(path[i + 2])) {
-    // UNC paths begin with two separators (but not 1 or 3)
-    i += 2;
-    for (int k = 0; k < 2; ++k) {
-      while (i < path.size() && !IsDirSep(path[i])) {
-        ++i;
-      }
-      while (i < path.size() && IsDirSep(path[i])) {
-        ++i;
-      }
-    }
-  } else if (i + 1 < path.size() && path[i + 1] == ':') {
-    i += 2;
-  }
-#endif
-  while (i < path.size() && IsDirSep(path[i])) {
-    ++i;
-  }
-  return i;
-}
-
-std::string GetRayTempDir() { return JoinPaths(GetUserTempDir(), "ray"); }
-
 std::string GetUserTempDir() {
   std::string result;
 #if defined(__APPLE__) || defined(__linux__)
diff --git a/src/ray/util/filesystem.h b/src/ray/util/filesystem.h
index 32db3243a..995bf5586 100644
--- a/src/ray/util/filesystem.h
+++ b/src/ray/util/filesystem.h
@@ -14,6 +14,7 @@
 
 #pragma once
 
+#include <filesystem>
 #include <string>
 #include <utility>
 
@@ -25,65 +26,36 @@ namespace ray {
 /// \return The portable directory separator (slash on all OSes).
 static inline char GetAltDirSep() { return '/'; }
 
-/// \return The platform directory separator (backslash on Windows, slash on other OSes).
-static inline char GetDirSep() {
-  char result;
-#ifdef _WIN32
-  result = '\\';
-#else
-  result = '/';
-#endif
-  return result;
-}
-
-/// \return The platform PATH separator (semicolon on Windows, colon on other OSes).
-static inline char GetPathSep() {
-  char result;
-#ifdef _WIN32
-  result = ';';
-#else
-  result = ':';
-#endif
-  return result;
-}
-
-/// Returns the executable binary suffix for the platform, if any.
-std::string GetExeSuffix();
-
 /// Equivalent to Python's os.path.basename() for file system paths.
 std::string GetFileName(const std::string &path);
 
-size_t GetRootPathLength(const std::string &path);
-
-/// \return A non-volatile temporary directory in which Ray can stores its files.
-std::string GetRayTempDir();
-
 /// \return The non-volatile temporary directory for the current user (often /tmp).
 std::string GetUserTempDir();
 
 /// \return Whether or not the given character is a directory separator on this platform.
 static inline bool IsDirSep(char ch) {
-  bool result = ch == GetDirSep();
+  bool result = ch == std::filesystem::path::preferred_separator;
 #ifdef _WIN32
   result |= ch == GetAltDirSep();
 #endif
   return result;
 }
 
-/// \return Whether or not the given character is a PATH separator on this platform.
-static inline bool IsPathSep(char ch) { return ch == GetPathSep(); }
-
 /// \return The result of joining multiple path components.
 template <class... Paths>
-std::string JoinPaths(std::string base, Paths... components) {
-  std::string to_append[] = {components...};
-  for (size_t i = 0; i < sizeof(to_append) / sizeof(*to_append); ++i) {
-    const std::string &s = to_append[i];
-    if (!base.empty() && !IsDirSep(base.back()) && !s.empty() && !IsDirSep(s[0])) {
-      base += GetDirSep();
+std::string JoinPaths(std::string base, const Paths &...components) {
+  auto join = [](auto &joined_path, const auto &component) {
+    // if the components begin with "/" or "////", just get the path name.
+    if (!component.empty() &&
+        component.front() == std::filesystem::path::preferred_separator) {
+      joined_path = std::filesystem::path(joined_path)
+                        .append(std::filesystem::path(component).filename().string())
+                        .string();
+    } else {
+      joined_path = std::filesystem::path(joined_path).append(component).string();
     }
-    base += s;
-  }
+  };
+  (join(base, std::string_view(components)), ...);
   return base;
 }
 }  // namespace ray
diff --git a/src/ray/util/filesystem_test.cc b/src/ray/util/filesystem_test.cc
index 3434f756a..179839af9 100644
--- a/src/ray/util/filesystem_test.cc
+++ b/src/ray/util/filesystem_test.cc
@@ -18,6 +18,21 @@
 
 namespace ray {
 
+namespace testing {
+template <class... Paths>
+std::string JoinPaths(std::string base, Paths... components) {
+  std::string to_append[] = {components...};
+  for (size_t i = 0; i < sizeof(to_append) / sizeof(*to_append); ++i) {
+    const std::string &s = to_append[i];
+    if (!base.empty() && !IsDirSep(base.back()) && !s.empty() && !IsDirSep(s[0])) {
+      base += std::filesystem::path::preferred_separator;
+    }
+    base += s;
+  }
+  return base;
+}
+}  // namespace testing
+
 TEST(FileSystemTest, PathParseTest) {
   ASSERT_EQ(GetFileName("."), ".");
   ASSERT_EQ(GetFileName(".."), "..");
@@ -32,6 +47,22 @@ TEST(FileSystemTest, PathParseTest) {
 #endif
 }
 
+TEST(FileSystemTest, JoinPathTest) {
+#ifdef _WIN32
+  auto old_path =
+      testing::JoinPaths(GetUserTempDir(), "hello", "\\subdir", "more", "", "last/");
+  auto new_path =
+      ray::JoinPaths(GetUserTempDir(), "hello", "\\subdir", "more", "", "last/");
+  ASSERT_EQ(old_path, new_path);
+#else
+  auto old_path =
+      testing::JoinPaths(GetUserTempDir(), "hello", "/subdir", "more", "", "last/");
+  auto new_path =
+      ray::JoinPaths(GetUserTempDir(), "hello", "/subdir", "more", "", "last/");
+  ASSERT_EQ(old_path, new_path);
+#endif
+}
+
 }  // namespace ray
 
 int main(int argc, char **argv) {
diff --git a/src/ray/util/logging.cc b/src/ray/util/logging.cc
index b2bb97156..ed9beffab 100644
--- a/src/ray/util/logging.cc
+++ b/src/ray/util/logging.cc
@@ -201,10 +201,6 @@ void RayLog::StartRayLog(const std::string &app_name, RayLogLevel severity_thres
 
   if (!log_dir_.empty()) {
     // Enable log file if log_dir_ is not empty.
-    std::string dir_ends_with_slash = log_dir_;
-    if (!ray::IsDirSep(log_dir_[log_dir_.length() - 1])) {
-      dir_ends_with_slash += ray::GetDirSep();
-    }
     std::string app_name_without_path = app_name;
     if (app_name.empty()) {
       app_name_without_path = "DefaultApp";
@@ -247,7 +243,7 @@ void RayLog::StartRayLog(const std::string &app_name, RayLogLevel severity_thres
       spdlog::drop(RayLog::GetLoggerName());
     }
     auto file_sink = std::make_shared<spdlog::sinks::rotating_file_sink_mt>(
-        dir_ends_with_slash + app_name_without_path + "_" + std::to_string(pid) + ".log",
+        JoinPaths(log_dir_, app_name_without_path + "_" + std::to_string(pid) + ".log"),
         log_rotation_max_size_, log_rotation_file_num_);
     sinks.push_back(file_sink);
   } else {
diff --git a/src/ray/util/logging_test.cc b/src/ray/util/logging_test.cc
index fc7c555e4..217166866 100644
--- a/src/ray/util/logging_test.cc
+++ b/src/ray/util/logging_test.cc
@@ -190,7 +190,7 @@ TEST(PrintLogTest, TestRayLogEveryMs) {
 
 TEST(PrintLogTest, LogTestWithInit) {
   // Test empty app name.
-  RayLog::StartRayLog("", RayLogLevel::DEBUG, ray::GetUserTempDir() + ray::GetDirSep());
+  RayLog::StartRayLog("", RayLogLevel::DEBUG, ray::GetUserTempDir());
   PrintLog();
   RayLog::ShutDownRayLog();
 }
@@ -198,8 +198,8 @@ TEST(PrintLogTest, LogTestWithInit) {
 // This test will output large amount of logs to stderr, should be disabled in travis.
 TEST(LogPerfTest, PerfTest) {
   RayLog::StartRayLog("/fake/path/to/appdire/LogPerfTest", RayLogLevel::ERROR,
-                      ray::GetUserTempDir() + ray::GetDirSep());
-  int rounds = 100000;
+                      ray::GetUserTempDir());
+  int rounds = 10;
 
   int64_t start_time = current_time_ms();
   for (int i = 0; i < rounds; ++i) {