Function GetFileCacheCapacity

src/kudu/server/server_base.cc:641–674

}

int64_t GetFileCacheCapacity(Env* env) {
  // Maximize this process' open file limit first, if possible.
  static std::once_flag once;
  std::call_once(once, [&]() {
    env->IncreaseResourceLimit(Env::ResourceLimitType::OPEN_FILES_PER_PROCESS);
  });

  uint64_t rlimit =
      env->GetResourceLimit(Env::ResourceLimitType::OPEN_FILES_PER_PROCESS);
  // See server_max_open_files.
  if (FLAGS_server_max_open_files == 0) {
    // Use file-max as a possible upper bound.
    faststring buf;
    uint64_t buf_val;
    if (ReadFileToString(env, "/proc/sys/fs/file-max", &buf).ok() &&
        safe_strtou64(buf.ToString(), &buf_val)) {
      rlimit = std::min(rlimit, buf_val);
    }

    // Callers of this function expect a signed 64-bit integer, and rlimit
    // is an uint64_t type, so we need to avoid overflow.
    // The percentage we currently use is 40% by default, and although in fact
    // 40% of any value of the `uint64_t` type must be less than `kint64max`,
    // but the percentage may be adjusted in the future, such as to 60%, so to
    // prevent accidental overflow, we cap rlimit here.
    return std::min((rlimit / 5) * 2, static_cast<uint64_t>(kint64max));
  }
  LOG_IF(FATAL, FLAGS_server_max_open_files > rlimit) <<
      Substitute(
          "Configured open file limit (server_max_open_files) $0 "
          "exceeds process open file limit (ulimit) $1",
          FLAGS_server_max_open_files, rlimit);
  return FLAGS_server_max_open_files;
}

#if defined(__linux__)
// See https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt