在 *nix 中，是什么导致“睡眠”？在最高指挥部？
是什么导致了我在 top 中看到的这些睡眠进程？如果我要调用 PHP 的 sleep() 函数，这会增加我在 top 中看到的 sleeping 计数吗？ 睡眠次数过多有什么坏处吗？
What causes these sleeping processes that I see in top? If I were to call PHP's sleep() function, would that add to the sleeping count I see in top? Are there any disadvantages to having a high number in sleeping?
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当一个进程被阻塞时，它就处于睡眠状态，正在等待某些事情。例如，它可能已调用
read()并等待数据从网络流到达。sleep()确实是让进程休眠一段时间的一种方法。然而，睡眠是除大量计算密集型进程之外的所有进程的正常状态 - 睡眠本质上是进程在不执行任何其他操作时所做的事情。大多数进程处于休眠状态是正常情况 - 如果情况并非如此，则往往表明您需要更多的 CPU 处理能力。A process is sleeping when it is blocked, waiting for something. For example, it might have called
read()and is waiting on data to arrive from a network stream.sleep()is indeed one way to have your process sleep for a while. Sleeping is, however, the normal state of all but heavily compute-bound processes - sleeping is essentially what a process does when it isn't doing anything else. It's the normal state of affairs for most of your processes to be sleeping - if that's not the case, it tends to indicate that you need more CPU horsepower.睡眠进程就像挂起的进程。
进程在以下情况下睡眠：
任何进程的状态都可以是：
状态 含义
R 可运行
T 已停止
P 等待调入
D 等待 I/O
S 睡眠
20秒
I 空闲 - 睡眠 >20 秒
Z 僵尸或已失效
A sleeping process is like suspended process.
A process sleeps when:
The status of any process can be:
Status Meaning
R Runnable
T Stopped
P Waiting on Pagein
D Waiting on I/O
S Sleeping < 20 seconds
I Idle - sleeping >20 seconds
Z Zombie or defunct
它们是目前不在 CPU 上运行的进程。这不一定是坏事。
如果您有大量（例如，服务器系统上有 10,000 个）进程处于睡眠状态，则用于跟踪它们的内存量等可能会降低系统对于非睡眠进程的效率。
否则，没关系。
大多数普通服务器系统大部分时间有 100 到 1000 个；这没什么大不了的。
仅仅因为他们现在没有采取任何行动，并不意味着他们很快就不会采取行动。将它们保存在内存中，做好准备，可以在需要时减少延迟。
They are processes which aren't running on the CPU right now. This is not necessarily a bad thing.
If you have huge numbers (10,000 on a server system, for example) of processes sleeping, the amount of memory etc used to keep track of them may make the system less efficient for non-sleeping processes.
Otherwise, it's fine.
Most normal server systems have 100 to 1000 much of the time; this is not a big deal.
Just because they're not doing anything just now doesn't mean they won't, very soon. Keeping them in memory, ready, reduces latency when they are required.
在这里更详细地说，
S状态意味着进程正在等待计时器或慢速设备，而D状态意味着它正在等待快速设备。设备。快速设备与慢速设备的构成并没有明确的定义，但一般来说，所有串行、网络和终端设备都是慢速设备，而磁盘是快速设备。
To go into a bit more detail here, the
Sstate means the process is waiting on a timer or a slow device, while theDstate means it is waiting on a fast device.What constitutes a fast device vs a slow device is not terribly well defined, but generally, all serial, network, and terminal devices are slow devices, while disks are fast devices.