single-threaded

来源： https://stackoverflow.com/questions/48035646/if-redis-is-single-threaded-how-can-it-be-so-fast

来源： https://stackoverflow.com/questions/48035646/if-redis-is-single-threaded-how-can-it-be-so-fast

问题 I've been reading John Resig's "Secrets of a JavaScript Ninja" and it explains that JavaScript is single-threaded. However, I tried testing this and I'm not sure what to take away from here: // executing this in browser (function () { // throw something into event queue setTimeout(function () { alert("This will be called back after 1 second."); }, 1000); // arbitrary loop to take up some time for (var i = 0; i < 10000; i += 1) { console.log(i); } })(); Maybe I'm not understanding exactly what

问题 JavaScript is a single threaded language and therefore it executes one command at a time. Asynchronous programming is being implemented via Web APIs ( DOM for event handling, XMLHttpRequest for AJAX calls, WindowTimers for setTimeout ) and the Event queue which are managed by the browser. So far, so good! Consider now, the following very simple code: $('#mybox').hide(17000); console.log('Previous command has not yet terminated!'); ... Could someone please explain to me the underlying

问题 I am having issues with my php server (my computer is the only connection). I initially thought part of the reason was because of too many ajax requests (I have a script that executes an ajax request per keystroke) so I implemented a design to control the flow of ajax requests into a queue. Below is my code: //global vars: activeAjaxThread = 0; //var describing ajax thread state ajaxQue = []; //array of ajax request objects in queue to be fired after the completion of the previous request

问题 rpc.call(mycallback); { //subsequent code block } How does the single threaded async callback work? When will the callback get called? Will the subsequent code block always finish executing before the callback is allowed to run (i.e. will the callback only run once all code has finished?)? 回答1: #1 javascript is single-thread, but the browser is not, so the js-thread sends the xhr call to the browser to resolve it, and the browser returns the control to it inmediately. #2 when the browser gets

问题 I am trying to understanding basics of Redis. One that that keep coming everywhere is, Redis is single threaded that makes things atomic.But I am unable to imagine how this is working internally.I have below doubt. Don't we design a server Single thread if it is IO bound application(like Node.js),where thread got free for another request after initiating IO operation and return data to client once IO operation is finished(providing concurrency). But in case of redis all data are available in

问题 Please look at this code. Single-threaded program: http://pastebin.com/KAx4RmSJ. Compiled with: g++ -lrt -O2 main.cpp -o nnlv2 Multithread with openMP: http://pastebin.com/fbe4gZSn Compiled with: g++ -lrt -fopenmp -O2 main_openmp.cpp -o nnlv2_openmp I tested it on a dual core system (so we have two threads running in parallel). But multi-threaded version is slower than the single-threaded one (and shows unstable time, try to run it few times). What's wrong? Where did I make mistake? Some

问题 Even after reading http://krondo.com/?p=1209 or Does an asynchronous call always create/call a new thread? I am still confused about how to provide asynchronous calls on an inherently single-threaded system. I will explain my understanding so far and point out my doubts. One of the examples I read was describing a TCP server providing asynch processing of requests - a user would call a method e.g. get(Callback c) and the callback would be invoked some time later. Now, my first issue here - we

问题 I'm new to nodeJS and was wondering about the single-instance model of Node. In a simple nodeJs application, when some blocking operation is asynchronously handled with callbacks, does the main thread running the nodeJs handle the callback as well?. If the request is to get some data off the database, and there are 100s of concurrent users, and each db operation takes couple of seconds, when the callback is finally fired (for each of the connections), is the main thread accepting these