如何衡量 Ruby 中的互斥锁争用？

Question

我最近发现自己试图诊断为什么特定的 Ruby 程序运行慢。最后证明它是由缩放问题引起的，导致对特定互斥锁的大量争用。

我想知道是否有任何工具可以用来使这个问题更容易诊断？我知道我可以使用 ruby-prof 来详细输出该程序的所有 100 多个线程花费的时间，但我很好奇是否有任何工具专门用于测量互斥锁Ruby?

中的争用

Answer 1

所以，如果知道如何使用 DTrace 执行此操作。

给定一个这样的 Ruby 程序：

# mutex.rb
mutex = Mutex.new
threads = []

threads << Thread.new do
  loop do
    mutex.synchronize do
      sleep 2
    end
  end
end

threads << Thread.new do
  loop do
    mutex.synchronize do
      sleep 4
    end
  end
end

threads.each(&:join)

我们可以像这样使用 DTrace 脚本：

/* mutex.d */
ruby$target:::cmethod-entry
/copyinstr(arg0) == "Mutex" && copyinstr(arg1) == "synchronize"/
{
  self->file = copyinstr(arg2);
  self->line = arg3;
}

pid$target:ruby:rb_mutex_lock:entry
/self->file != NULL && self->line != NULL/
{
  self->mutex_wait_start = timestamp;
}

pid$target:ruby:rb_mutex_lock:return
/self->file != NULL && self->line != NULL/
{
  mutex_wait_ms = (timestamp - self->mutex_wait_start) / 1000;
  printf("Thread %d acquires mutex %d after %d ms - %s:%d\n", tid, arg1, mutex_wait_ms, self->file, self->line);
  self->file = NULL;
  self->line = NULL;
}

当我们运行这个脚本针对Ruby程序时，我们会得到这样的信息：

$ sudo dtrace -q -s mutex.d -c 'ruby mutex.rb'

Thread 286592 acquires mutex 4313316240 after 2 ms - mutex.rb:14
Thread 286591 acquires mutex 4313316240 after 4004183 ms - mutex.rb:6
Thread 286592 acquires mutex 4313316240 after 2004170 ms - mutex.rb:14
Thread 286592 acquires mutex 4313316240 after 6 ms - mutex.rb:14
Thread 286592 acquires mutex 4313316240 after 4 ms - mutex.rb:14
Thread 286592 acquires mutex 4313316240 after 4 ms - mutex.rb:14
Thread 286591 acquires mutex 4313316240 after 16012158 ms - mutex.rb:6
Thread 286592 acquires mutex 4313316240 after 2002593 ms - mutex.rb:14
Thread 286591 acquires mutex 4313316240 after 4001983 ms - mutex.rb:6
Thread 286592 acquires mutex 4313316240 after 2004418 ms - mutex.rb:14
Thread 286591 acquires mutex 4313316240 after 4000407 ms - mutex.rb:6
Thread 286592 acquires mutex 4313316240 after 2004163 ms - mutex.rb:14
Thread 286591 acquires mutex 4313316240 after 4003191 ms - mutex.rb:6
Thread 286591 acquires mutex 4313316240 after 2 ms - mutex.rb:6
Thread 286592 acquires mutex 4313316240 after 4005587 ms - mutex.rb:14
...

我们可以收集此输出并使用它来获取有关哪些互斥量引起最多争用的信息。

如何衡量 Ruby 中的互斥锁争用？

How can I measure mutex contention in Ruby?

ruby

concurrency

monitoring

mutex