Squashed commit of the following:

commit b96ddedf4ffbba57faaaf8bf18781a7abfb9d4c1
Author: Carl Pearson <pearson@illinois.edu>
Date:   Mon Sep 23 16:53:54 2019 -0500

    add newline to result.hpp

commit c7e9f6ff4775bf86f9af216cbe311f65bf985f63
Author: Carl Pearson <pearson@illinois.edu>
Date:   Mon Sep 23 16:53:09 2019 -0500

    add EPERM to fs operations

commit bac918fd022006cad0da899c06ac31e9db59a2fb
Author: Carl Pearson <pearson@illinois.edu>
Date:   Mon Sep 23 16:49:25 2019 -0500

    add filesystem cache interface

include/perfect/cpu_set.hpp

@@ -0,0 +1,361 @@
+#pragma once
+
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include <algorithm>
+#include <cstring>
+#include <fstream>
+#include <set>
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include "init.hpp"
+#include "result.hpp"
+
+#define SUCCESS_OR_RETURN(stmt) \
+{\
+  Result _ret; \
+  _ret = (stmt); \
+if (_ret != Result::SUCCESS) {\
+  return _ret;\
+}\
+}
+
+std::set<int> operator-(const std::set<int> &lhs, const std::set<int> &rhs) {
+  std::set<int> result;
+  for (auto e : lhs) {
+    if (0 == rhs.count(e)) {
+      result.insert(e);
+    }
+  }
+  return result;
+}
+
+std::string remove_space(const std::string &s) {
+  std::string result;
+
+  for (auto c : s) {
+    if (!isspace(c)) {
+      result += c;
+    }
+  }
+  return result;
+}
+
+// like "8" or "8-10"
+std::set<int> parse_token(const std::string &token) {
+  // std::cerr << "parse_token: parsing '" << s << "'\n";
+  std::set<int> result;
+
+  std::string s = token;
+  // ignore empty string
+  if (s.empty()) {
+    return result;
+  }
+
+  // remove newline
+  s = remove_space(s);
+
+  size_t pos = 0;
+
+  int first = std::stoi(s, &pos);
+  // std::cerr << "parse_token: found '" << first << "'\n";
+
+  // single int
+  if (pos == s.length()) {
+    result.insert(first);
+    return result;
+  }
+
+  // next char should be a "-"
+  assert(s[pos] == '-');
+
+  std::string rest = s.substr(pos + 1);
+  int second = std::stoi(rest, &pos);
+  // std::cerr << "parse_token: found '" << second << "'\n";
+
+  // insert first-second
+  // std::cerr << "parse_token: range " << first << " to " << second << "\n";
+  for (int i = first; i <= second; ++i) {
+    result.insert(i);
+  }
+  return result;
+}
+
+std::set<int> parse_cpuset(const std::string &s) {
+  // std::cerr << "parse_cpuset: parsing '" << s << "'\n";
+  std::set<int> result;
+
+  std::string token;
+  std::stringstream ss(s);
+  while (std::getline(ss, token, ',')) {
+
+    if ("\n" != token) {
+      auto newCpus = parse_token(token);
+      for (auto cpu : newCpus) {
+        result.insert(cpu);
+      }
+    }
+  }
+
+  return result;
+}
+
+// http://man7.org/linux/man-pages/man7/cpuset.7.html
+namespace perfect {
+class CpuSet {
+public:
+  std::string path_;
+  std::set<int> cpus_;
+  std::set<int> mems_;
+  CpuSet *parent_;
+
+  // make sure cpuset is initialized
+  static Result init() {
+
+    // check for "nodev cpuset" in /proc/filesystems
+
+    // mkdir /dev/cpuset
+    if (mkdir("/dev/cpuset", S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) {
+      switch (errno) {
+      case EEXIST: {
+        // okay
+        break;
+      }
+      case EACCES:
+        // std::cerr << "access error in mkdir: " << strerror(errno) << "\n";
+        return Result::NO_PERMISSION;
+      case ENOENT:
+      case EROFS:
+      default:
+        std::cerr << "unhandled error in mkdir: " << strerror(errno) << "\n";
+        return Result::UNKNOWN;
+      }
+
+      // mount -t cpuset none /dev/cpuset
+      if (mount("none", "/dev/cpuset", "cpuset", 0, nullptr)) {
+        switch (errno) {
+        case EEXIST: {
+          // okay
+          break;
+        }
+        case EBUSY: {
+          // FIXME: something is mounted here, assume it is what we want
+          // std::cerr << "EBUSY in mount: " << strerror(errno) << "\n";
+          return Result::SUCCESS;
+        }
+        case EPERM: {
+        // std::cerr << "EPERM in mount: " << strerror(errno) << "\n";
+        return Result::NO_PERMISSION;
+        }
+        case ENOENT:
+        case EROFS:
+        default:
+          std::cerr << "unhandled error in mount: " << strerror(errno) << "\n";
+          return Result::UNKNOWN;
+        }
+      }
+    }
+    return Result::SUCCESS;
+  }
+
+  std::string get_raw_cpus() {
+    std::ifstream is(path_ + "/cpuset.cpus");
+    std::stringstream ss;
+    ss << is.rdbuf();
+    return remove_space(ss.str());
+  }
+
+  std::string get_raw_mems() {
+    std::ifstream is(path_ + "/cpuset.mems");
+    std::stringstream ss;
+    ss << is.rdbuf();
+    return remove_space(ss.str());
+  }
+
+  std::set<int> get_cpus() { return parse_cpuset(get_raw_cpus()); }
+
+  std::set<int> get_mems() { return parse_cpuset(get_raw_mems()); }
+
+  // migrate the caller task from this cpu set to another
+  Result migrate_self_to(CpuSet &other) {
+    // enable memory migration in other
+    other.enable_memory_migration();
+
+    // get my pid
+    pid_t self = this_task();
+
+    // read this tasks and write each line to other.tasks
+    std::ifstream is(path_ + "/tasks");
+    std::string line;
+    while (std::getline(is, line)) {
+      line = remove_space(line);
+      if (std::to_string(self) == line) {
+        // std::cerr << "migrating self task " << line << " to " << other.path
+        //           << "\n";
+        other.write_task(line);
+        return Result::SUCCESS;
+      }
+    }
+    return Result::NO_TASK;
+  }
+
+  // migrate tasks in this cpu set to another
+  Result migrate_tasks_to(CpuSet &other) {
+    // enable memory migration in other
+    SUCCESS_OR_RETURN(other.enable_memory_migration());
+
+    // read this tasks and write each line to other.tasks
+    std::ifstream is(path_ + "/tasks");
+    std::string line;
+    while (std::getline(is, line)) {
+      // std::cerr << "migrating task " << line << " to " << other.path << "\n";
+      other.write_task(line);
+    }
+
+    return Result::SUCCESS;
+  }
+
+  Result enable_memory_migration() {
+    std::ofstream ofs(path_ + "/" + "cpuset.memory_migrate");
+    ofs << "1";
+    ofs.close();
+    if (ofs.fail()) {
+    switch (errno) {
+    case EACCES:
+      return Result::NO_PERMISSION;
+    case ENOENT:
+      return Result::NOT_SUPPORTED;
+    default:
+      return Result::UNKNOWN;
+    }
+  }
+    return Result::SUCCESS;
+  }
+
+  void write_task(const std::string &task) {
+    // write `task` to path/tasks
+    std::ofstream os(path_ + "/tasks");
+    os << task << "\n";
+  }
+
+  // object representing the root CPU set
+  static Result get_root(CpuSet &root) {
+    SUCCESS_OR_RETURN(CpuSet::init());
+    root.path_ = "/dev/cpuset";
+    root.parent_ = nullptr;
+    return Result::SUCCESS;
+  }
+
+  // the ID of this task
+  static pid_t this_task() { return getpid(); }
+
+  Result make_child(CpuSet &child, const std::string &name) {
+
+    if (mkdir((path_ + "/" + name).c_str(),
+              S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) {
+      switch (errno) {
+      case EEXIST: {
+        // okay
+        break;
+      }
+      case EACCES:
+        return Result::NO_PERMISSION;
+      case ENOENT:
+      case EROFS:
+      default:
+        return Result::UNKNOWN;
+      }
+    }
+
+    child.path_ = path_ + "/" + name;
+    child.parent_ = this;
+    return Result::SUCCESS;
+  }
+
+  Result enable_cpu(const int cpu) {
+    std::set<int> cpus = get_cpus();
+    cpus.insert(cpu);
+    return write_cpus(cpus);
+  }
+
+  Result enable_cpus(const std::set<int> &cpus) {
+    std::set<int> finalCpus = get_cpus();
+    for (auto cpu : cpus) {
+      finalCpus.insert(cpu);
+    }
+    return write_cpus(finalCpus);
+  }
+
+  // FIXME: check error
+  Result write_cpus(std::set<int> cpus) {
+    std::ofstream os(path_ + "/cpuset.cpus");
+    bool comma = false;
+    for (auto cpu : cpus) {
+      if (comma)
+        os << ",";
+      os << cpu << "-" << cpu;
+      comma = true;
+    }
+    return Result::SUCCESS;
+  }
+
+  // FIXME: check write
+  Result write_mems(std::set<int> mems) {
+    std::ofstream os(path_ + "/cpuset.mems");
+    bool comma = false;
+    for (auto mem : mems) {
+      if (comma)
+        os << ",";
+      os << mem << "-" << mem;
+      comma = true;
+    }
+    return Result::SUCCESS;
+  }
+
+  Result enable_mem(const int mem) {
+    std::set<int> mems = get_mems();
+    mems.insert(mem);
+    return write_mems(mems);
+  }
+
+  Result enable_mems(const std::set<int> &mems) {
+    std::set<int> finalMems = get_mems();
+    for (auto mem : mems) {
+      finalMems.insert(mem);
+    }
+    return write_mems(finalMems);
+  }
+
+  Result destroy() {
+    // remove all child cpu sets
+
+    // move all attached processes back to parent
+    assert(parent_);
+    migrate_tasks_to(*parent_);
+
+    // remove with rmdir
+    if (rmdir(path_.c_str())) {
+      switch (errno) {
+      default:
+        std::cerr << "unhandled error in rmdir: " << strerror(errno) << "\n";
+        return Result::UNKNOWN;
+      }
+    }
+
+    path_ = "";
+    return Result::SUCCESS;
+  }
+
+
+};
+
+  std::ostream &operator<<(std::ostream &s, const CpuSet &c) {
+    s << c.path_;
+    return s;
+  }
+
+} // namespace perfect

include/perfect/detail/fs.hpp

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <fstream>
+#include <string>
+
+#include "perfect/result.hpp"
+
+namespace perfect {
+namespace detail {
+Result write_str(const std::string &path, const std::string &val) {
+  std::ofstream ofs(path);
+  if (ofs.fail()) {
+    return Result::NOT_SUPPORTED;
+  }
+
+  ofs << val;
+  ofs.close();
+  if (ofs.fail()) {
+    switch (errno) {
+    case EACCES:
+    std::cerr << "EACCES when writing to " << path << "\n";
+      return Result::NO_PERMISSION;
+    case EPERM:
+      std::cerr << "EPERM when writing to " << path << "\n";
+      return Result::NO_PERMISSION;
+    case ENOENT:
+      return Result::NOT_SUPPORTED;
+    default:
+      return Result::UNKNOWN;
+    }
+  }
+  return Result::SUCCESS;
+}
+
+} // namespace detail
+} // namespace perfect

include/perfect/drop_caches.hpp

@@ -0,0 +1,43 @@
+#pragma once
+
+#include <unistd.h>
+
+#include <fstream>
+#include <iostream>
+
+#include "result.hpp"
+#include "init.hpp"
+#include "detail/fs.hpp"
+
+namespace perfect {
+
+enum DropCaches_t {
+    PAGECACHE = 0x1,
+    ENTRIES = 0x2
+};
+
+
+// commit filesystem caches to disk
+Result sync() {
+    // http://man7.org/linux/man-pages/man2/sync.2.html
+    ::sync(); // always successful
+    return Result::SUCCESS;
+}
+
+Result drop_caches(const DropCaches_t mode) {
+    using detail::write_str;
+    const std::string path = "/proc/sys/vm/drop_caches";
+    if (mode & PAGECACHE & ENTRIES) {
+        PERFECT_SUCCESS_OR_RETURN(write_str(path, "3"));
+    } else if (mode & PAGECACHE) {
+        PERFECT_SUCCESS_OR_RETURN(write_str(path, "1"));
+    } else if (mode & ENTRIES) {
+        PERFECT_SUCCESS_OR_RETURN(write_str(path, "2"));
+    } else {
+        std::cerr << "unexpected mode: " << mode << "\n";
+        return Result::UNKNOWN;
+    }
+    return Result::SUCCESS;
+}
+
+}

include/perfect/result.hpp

@@ -78,3 +78,12 @@ inline void check(Result result, const char *file, const int line) {
 } // namespace perfect
 
 #define PERFECT(stmt) check(stmt, __FILE__, __LINE__);
+
+#define PERFECT_SUCCESS_OR_RETURN(stmt) \
+{\
+  Result _ret; \
+  _ret = (stmt); \
+if (_ret != Result::SUCCESS) {\
+  return _ret;\
+}\
+}