Redis fork copy-on-write array

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Redis fork copy-on-write array

If parent dies before children have exited, children can become zombie processes All threads die when the process dies no chance of zombies More expensive for forked processes to switch context since OS needs to save and reload everything Threads have considerably less overhead since they share address space and memory Forked processes are given a new virtual memory space process isolation Threads share the same memory, so need to control and deal with concurrent memory issues Requires inter-process communication Can "communicate" via queues and shared memory Slower to create and destroy Faster to create and destroy Easier to code and debug Can be significantly more complex to code and debug Examples of Ruby solutions that use multiple processes: A Redis-backed Ruby library for creating background jobs, placing them on multiple queues, and processing them later.

Examples of Ruby solutions that use multithreading: A full-featured background processing framework for Ruby. It aims to be simple to integrate with any modern Rails application and much higher performance than other existing solutions.

A Ruby web server built for concurrency.

redis fork copy-on-write array

A very fast and simple Ruby web server. This new process is scheduled at the operating system level, so it can run concurrently with the original process, just as any other independent process can.

This code now yields the following results again, on a quad-core processor with MRI Ruby 2. If your app uses 20MB of memory, for example, forking it times could potentially consume as much as 2GB of memory!

Also, although multithreading has its own complexities as well, there are a number of complexities that need to be considered when using forksuch as shared file descriptors and semaphores between parent and child forked processesthe need to communicate via pipes, and so on.

Ruby Concurrency and Parallelism in Multithreaded Apps: A Tutorial | Toptal

Multiple threads within a single process have considerably less overhead than a corresponding number of processes since they share address space and memory. Why is this producing almost the same results as we got when we ran the code synchronously?

The Global Interpreter Lock is a mechanism used in computer language interpreters to synchronize the execution of threads so that only one thread can execute at a time. An interpreter which uses GIL will always allow exactly one thread and one thread only to execute at a time, even if run on a multi-core processor.

So back to our problem, how can we exploit multithreading in Ruby to improve performance in light of the GIL? Ruby concurrency without parallelism can still be very useful, though, for tasks that are IO-heavy e.

There is a reason threads were, after all, invented nd used even before multi-core servers were common.

聊聊并发(二)Java SE中的Synchronized | 并发编程网 –

To prove the point, here are the results we get when we run the exact same threaded version of the code as before, but this time run it on JRuby instead of CRuby: That would indeed be nice if it were true, but the reality is that threads are not free and so, sooner or later, you will run out of resources.

I got an error with my OS X Resource temporarily unavailable ThreadError As expected, sooner or later we start thrashing or run out of resources entirely. So the scalability of this approach is clearly limited. Thread Pooling Fortunately, there is a better way; namely, thread pooling.

A thread pool is a group of pre-instantiated, reusable threads that are available to perform work as needed.Effectively, in the middle of a bulk load, Redis does a fork and relies on the COW (copy-on-write) feature in Linux so that old parent pages are left untouched while the background process writes to disk.

Ben Nadel demonstrates that Redis will not store empty sets or empty hashes. And, whats more, will delete sets and hashes when their last members or key are deleted, respectively. Redis Doesn't Store Empty Sets Or Hashes (And Will Delete Empty Sets And Hashes) By Ben Nadel on December 1, here the EXEC returns an Array of results.

But yes in case of recent Linux with MMU the fork(2) will work with copy-on-write.

The reason for this comes down to the simple fact that redis-server is designed to make use of the cheap linux fork/copy-on-write functionality to perform background saving (and possibly other functionality). Copy-On-Write简称COW,是一种用于程序设计中的优化策略。其基本思路是,从一开始大家都在共享同一个内容,当某个人想要修改这个内容的时候,才会真正把内容Copy出去形成一个新的内容然后再改,这是一种延时懒惰策略。. Liste von Dateiendungen mit alphatisch sortiert mit Erklärung. Was bedeutet die File Extension?

It will only (allocate and) copy a few system structures and the page table, but the heap pages actually point to the ones of the parent until written.

Redis server commands are basically used to manage Redis server.

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Example. Following example explains how we can get all statistics and information about the server. The Redis community uses a Reddit sub for news and certain announcements (that also always go to the ML): /r/redis sub on Reddit. Meet people interested in Redis in the #redis .

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