blocks|key|1454611|text|例如，在不阻塞用户界面的情况下执行CPU密集型任务。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1454612|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Performing a CPU intensive task without blocking the user interface, for example.

blocks|key|682467|text|任何可能等待资源的应用程序(例如，从网络套接字或磁盘设备阻塞I/O+)都可以从线程中受益。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|682468|在这种情况下，慢操作上的线程阻塞可以在其他线程继续运行时进入休眠状态(包括在某些操作系统下，GUI线程，如果操作系统不能与它联系一段时间，它将提供使用机会破坏它，认为它在某种程度上陷入了僵局)。|682469|所以它并不仅仅适用于多核机器。|682470|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

Any application in which you may be waiting around for a resource (for example, blocking I/O from network sockets or disk devices) can benefit from threading.

In that case the thread blocking on the slow operation can be put to sleep while other threads continue to run (including, under some operating systems, the GUI thread which, if the OS cannot contact it for a while, will offer the use the chance to destroy it, thinking it's deadlocked somehow).

So it's not just for multi-core machines at all.

blocks|key|1421388|text|一个有趣的例子是，一个need服务器--您需要能够处理与彼此无关的多个传入连接。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|1421389|entityMap^0|8|A|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

An interesting example is a webserver - you need to be able to handle multiple incoming connections that have nothing to do with each other.

blocks|key|1454788|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1454789|什么类型的非性能相关问题值得线程处理？|blockquote|1454790|1454791|1454792|Web应用程序就是典型的例子。每个用户请求在概念上都是一个新线程。与性能无关，这只是设计的自然适合。|1454793|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|-4|4|5|6|J|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|K|7|@]|8|@]|9|$]]|$1|D|3|-4|4|5|6|L|7|@]|8|@]|9|$]]|$1|E|3|-4|4|5|6|M|7|@]|8|@]|9|$]]|$1|F|3|G|4|5|6|N|7|@]|8|@]|9|$]]|$1|H|3|-4|4|5|6|O|7|@]|8|@]|9|$]]]|I|$]]

<blockquote>
 what kinds of non-performance related
 problems justify threading?
</blockquote>

Web applications are the classic example. Each user request is conceptually a new thread. Nothing to do with performance, it's just a natural fit for the design.

blocks|key|1455037|text|与非阻塞代码相比，阻塞代码通常更容易编写，更易于阅读(因此也更易于维护)。然而，使用阻塞代码将您限制在单个执行路径上，并且还会锁定用户界面(提到)和其他IO端口等内容。在这些情况下，线程处理是一种优雅的解决方案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1455038|要考虑多线程的另一种情况是，当您有几个应该管理的近同步IO通道时:使用多个线程(通常是本地消息队列)可以获得更清晰的代码。|1455039|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Blocking code is usually much simpler to write and easier to read (and therefore maintain) than non-blocking code. Yet, using blocking code limits you to a single execution path and also locks out things like user interface (mentioned) and other IO ports. Threading is an elegant solution in these cases.

Another case when multithreading is to be considered is when you have several near-synchronous IO channels that should be managed: using multiple threads (and usually a local message queue) allows for much clearer code.

blocks|key|1454919|text|以下是我启动线程的几个具体而简单的场景..。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1454920|1454921|用户长期运行的报表请求。当报告提交时，它被放置在一个队列中，由一个单独的线程处理。然后，用户可以在应用程序中继续，稍后再检查以查看其报表的状态，不会留下“处理.”。页或图标。|ordered-list-item|1454922|线程迭代缓存存储，删除已过期或不再需要的数据。应用程序中的线程任务与特定用户的任何处理无关，但在整个应用程序运行时maintenance.|1454923|although，中的一部分|1454924|1454925|我同意，仅仅为了线程而线程不是一个好主意，如果做得不好，它可以在您的应用程序中引入问题，但是它是解决一些问题的非常有用的工具。|1454926|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|P|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|Q|8|@]|9|@]|A|$]]|$1|F|3|G|5|E|7|R|8|@]|9|@]|A|$]]|$1|H|3|I|5|E|7|S|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|T|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

Here are a couple of specific and simple scenarios where I have launched threads...

<ol>
<li>A long running report request by the user. When the report is submitted, it is placed in a queue to be processed by a separate thread. The user can then go on within the application and check back later to see the status of their report, they aren't left with a "Processing..." page or icon.</li>
<li>A thread that iterates cache storage, removing data that has expired or no longer needed. The thread's job within the application is independent of any processing for a specific user, but part of the overall application run-time maintenance.</li>
<li>although, not specifically a threading scenario, logging within our web site is handed off to a parallel process, so the throughput of the web site isn't hindered by the time it takes to record log data.</li>
</ol>

I agree that threading just for threadings sake isn't a good idea and it can introduce problems within your application if isn't done properly, but it is an extremely useful tool for solving some problems.

blocks|key|1454962|text|每当您需要调用某个外部组件时(无论是数据库查询、第三方库、操作系统原语等等)。它只提供同步/阻塞接口，或者使用异步接口，不值得额外的麻烦和痛苦--而且您还需要某种形式的并发性--例如，在服务器中服务多个客户端或保持GUI仍然响应。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1454963|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Whenever you need to call some external component (be it a database query, a 3. party library, an operating system primitive etc.) that only provides a synchronous/blocking interface or using the asynchronous interface not worth the extra trouble and pain - and you also need some form of concurrency - e.g. serving multiple clients in a server or keep the GUI still responsive.

blocks|key|1421838|text|那么，你怎么知道你的应用程序是否会运行在多核系统上呢？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1421839|除此之外，还有很多进程占用时间，但不需要CPU。例如写到磁盘或网络。谁想在GUI中按下一个按钮，然后坐在那里等待网络连接。即使在单个核心计算机上，拥有单独的IO线程也大大改善了用户体验。您至少总是希望为UI提供一个单独的线程。|1421840|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Well, how do you know if you're app is going to run on a multi-core system or not? 

Beyond that, there are a lot of processes that take up time, but don't require the CPU. Such as writing to a disk or networking. Who wants to push a button in a GUI and then have to sit there and wait for a network connection. Even on a single core machine, having a separate IO thread greatly improves user experience. You always at least want a separate thread for the UI.

blocks|key|1421358|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1421359|+--然而，许多人似乎认为，程序中可以线程化的每个任务都应该线程化，即使是在单个核心系统上也是如此。|blockquote|1421360|1421361|1421362|“很多人”。谁?|1421363|而且，根据我的经验，许多应该多线程的程序都不是(特别是游戏)。我有一个i7，但大多数游戏仍然只使用我的一个核心)，所以我不知道你在说什么。当然，像calc.exe这样的程序不是多线程(或者，如果是的话，一个线程完成99%25的工作)。|offset|length|style|CODE|1421364|例如，|1421365|在不阻塞用户界面的情况下执行CPU密集型任务。|1421366|1421367|1421368|是的，这是真的，但这是相当容易实现的，这不是OP所指的(因为，在本例中，1线程完成了几乎所有的工作，而您只需要很少的互斥)|1421369|entityMap^0|0|0|0|0|0|21|8|0|0|0|0|0|0^^$0|@$1|2|3|-4|4|5|6|X|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|Y|7|@]|8|@]|9|$]]|$1|D|3|-4|4|5|6|Z|7|@]|8|@]|9|$]]|$1|E|3|-4|4|5|6|10|7|@]|8|@]|9|$]]|$1|F|3|G|4|5|6|11|7|@]|8|@]|9|$]]|$1|H|3|I|4|5|6|12|7|@$J|13|K|14|L|M]]|8|@]|9|$]]|$1|N|3|O|4|5|6|15|7|@]|8|@]|9|$]]|$1|P|3|Q|4|C|6|16|7|@]|8|@]|9|$]]|$1|R|3|-4|4|5|6|17|7|@]|8|@]|9|$]]|$1|S|3|-4|4|5|6|18|7|@]|8|@]|9|$]]|$1|T|3|U|4|5|6|19|7|@]|8|@]|9|$]]|$1|V|3|-4|4|5|6|1A|7|@]|8|@]|9|$]]]|W|$]]

<blockquote>
 Yet many people seem to think that
 every task in a program that can be
 threaded should be threaded, even on a
 single core system.
</blockquote>

"Many people"... Who?

Also from my experience many many programs that should be multithreaded aren't (especially games.. I have an i7 and yet most games still use only 1 of my cores), so I'm not sure what you're talking about. Definitely programs like <code>calc.exe</code> are not multithread (or, if they are, 1 thread does 99% of the work).

<blockquote>
 Performing a CPU intensive task
 without blocking the user interface,
 for example.
</blockquote>

Yes, this is true but this is fairly easy to implement and it's not what the OP is referring to (since, in this case, 1 thread does almost all the work and you only need very few mutexes)

Threads make the design, implementation and debugging of a program significantly more difficult.

Yet many people seem to think that every task in a program that can be threaded should be threaded, even on a single core system.

I can understand threading something like an MPEG2 decoder that's going to run on a multicore cpu ( which I've done ), but what can justify the significant development costs threading entails when you're talking about a single core system or even a multicore system if your task doesn't gain significant performance from a parallel implementation?

Or more succinctly, what kinds of non-performance related problems justify threading?

Edit

Well I just ran across one instance that's not CPU limited but threads make a big difference:

<a href="https://stackoverflow.com/questions/2410388/tcp-http-and-the-multi-threading-sweet-spot">TCP, HTTP and the Multi-Threading Sweet Spot</a>

Multiple threads are pretty useful when trying to max out your bandwidth to another peer over a high latency network connection. Non-blocking I/O would use significantly less local CPU resources, but would be much more difficult to design and implement.

What Use are Threads Outside of Parallel Problems on MultiCore Systems?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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线程使得程序的设计、实现和调试变得非常困难。然而，许多人似乎认为，程序中可以线程化的每一个任务都应该线程化，即使是在单个核心系统上也是如此。我可以理解线程化，比如将在多核cpu上运行的MPEG2解码器(我已经这样做了)，但是如果您的任务没有从并行实现中获得显着的性能，那么当您谈论单个核心系统甚至多核系统时，线程化所带来的巨大开发成本有什么理由呢？或者更简洁地说，什么样的与性能不相关的问题值得线程处

问在MultiCore系统中，线程在并行问题之外有什么用途？
EN

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