# Can anyone \*really\* explain opcode caching with PHP? **URL:** \ **Category:** NGINX\ **Created:** [March 7, 2012, 4:13am UTC](https://www.ruby-forum.com/t/can-anyone-really-explain-opcode-caching-with-php/217637 "2012-03-07T04:13:56Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![dubstep](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/cdc98d/32.png) [@dubstep](https://www.ruby-forum.com/u/dubstep)\ **Post date:** [March 7, 2012, 4:13am UTC](https://www.ruby-forum.com/t/can-anyone-really-explain-opcode-caching-with-php/217637/1 "2012-03-07T04:13:56Z")
Hi folks Thinking of abandoning mod\_php for the wonderful world of nginx, but googling the issue of opcode caching with fastcgi is proving surprisingly confusing: there’s a lot of conflicting information out there. My basic question is this: what is the most performant, memory-efficient, Slashdot resistant way to set up nginx for running a complex PHP app? More specifically: 1. Why cache? I understood that a fastcgi process compiles the app into memory, and serves it from there till it’s recycled after max\_requests. So what’s the value of opcode caching? To speed up one request in 500? But I’ve seen benchmarks that claim an opcode cache with nginx offers 50% savings on memory and response time. Where would these savings be coming from? No one explains… 2. What cache? Nginx/PHP setup tutorials either omit opcode caching or recommend xcache, without explaining why. There’s a lot of conflicting information about whether each process needs its own cache (very memory intensive?) or whether processes can share a cache. Some bloggers claim that Xcache handles this better than APC, but again, no one explains how or why. Can anyone offer an authoritative answer to this? So is opcode caching effective with fastcgi? If so, how does it work, and what setup plays best with nginx? I would be more than grateful if anyone can make sense of this. Also, can I please suggest this as a candidate for the nginx FAQs? Judging by what I’ve been reading, I’m not the only one who’se confused by this… Posted at Nginx Forum: > **[Can anyone \*really\* explain opcode caching with PHP?](https://forum.nginx.org/read.php?2,223556,223556#msg-223556)** > > Hi folks Thinking of abandoning mod\_php for the wonderful world of nginx, but googling the issue of opcode caching with fastcgi is proving surprisingly confusing: there's a lot of conflicting information out there. My basic question is this: what is... ---
**Author:** ![gcaplan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/8baadc/32.png) [@gcaplan](https://www.ruby-forum.com/u/gcaplan)\ **Post date:** [March 7, 2012, 10:47am UTC](https://www.ruby-forum.com/t/can-anyone-really-explain-opcode-caching-with-php/217637/2 "2012-03-07T10:47:18Z")
> Hi folks > > Thinking of abandoning mod\_php for the wonderful world of nginx, but > googling the issue of opcode caching with fastcgi is proving > surprisingly confusing: there’s a lot of conflicting information out > there. > > My basic question is this: what is the most performant, > memory-efficient, Slashdot resistant way to set up nginx for running a > complex PHP app? You have to take in account one fundamental point: mod\_php is often see as “easy” because it get the apache’s adaptive process spawning. That means you have not to take in account how much processes to dedicate to php requests. Apache will spawn processes on demand. With nginx you have a proxy talking to a set of processes (via various protocols). The default php fastcgi server does not have adaptive process spawning, so you have to preallocate them, carefully choosing the number. This often smashes even experienced apache “sysadmin”, used to not care that aspect. (i remember one guy working on one of fortune 500 company blaming nginx on that list). I still have customer (experienced php developers) that still not get the “multiprocess” concept. I answer your questions below > More specifically: > > 1. Why cache? I understood that a fastcgi process compiles the app into > memory, and serves it from there till it’s recycled after max\_requests. > So what’s the value of opcode caching? To speed up one request in 500? > But I’ve seen benchmarks that claim an opcode cache with nginx offers > 50% savings on memory and response time. Where would these savings be > coming from? No one explains… fastcgi is only a communication protocol from nginx to your app (the php server). I am not a big fan of opcode caching, but i can assure you that it works in php fastcgi server, php-fpm and uWSGI. It really works whenever your php processes are not recycled (that is why it will never works on CGI mode) > anyone can make sense of this. Also, can I please suggest this as a > candidate for the nginx FAQs? Judging by what I’ve been reading, I’m not > the only one who’se confused by this… again, caching fully works whenever you do not recycle your processes, so you will not have problems with that. I only suggest you to choose a more advanced server, like php-fpm or uWSGI (even if it is very new in the php world), as the old-style embedded php fastcgi-server has very few features (read: none) – Roberto De Ioris > **[unbit - Overview](https://github.com/unbit)** > > makers of uWSGI and many more open source projects - unbit ---
**Author:** ![gcaplan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/8baadc/32.png) [@gcaplan](https://www.ruby-forum.com/u/gcaplan)\ **Post date:** [March 7, 2012, 11:11am UTC](https://www.ruby-forum.com/t/can-anyone-really-explain-opcode-caching-with-php/217637/3 "2012-03-07T11:11:01Z")
Am Wed, 7 Mar 2012 10:46:23 +0100 schrieb “Roberto De Ioris” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > I only suggest you to choose a more advanced server, like php-fpm or > uWSGI (even if it is very new in the php world), > as the old-style embedded php fastcgi-server has very few features > (read: none) Additionally, one has to take into account that opcode-caching and the like that zend, apc etc. do only usually gives you a couple of percents of increased performance. When you get “slashdotted”, that is basically useless. What you have to do is aggressive output-caching via varnish or nginx (we haven’t done this, yet, but I assume it’s possible since some time, too). That will give you much (x-times) more performance than an opcode-cache will ever be able to. Rainer ---
**Author:** ![gcaplan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/8baadc/32.png) [@gcaplan](https://www.ruby-forum.com/u/gcaplan)\ **Post date:** [March 8, 2012, 4:14am UTC](https://www.ruby-forum.com/t/can-anyone-really-explain-opcode-caching-with-php/217637/4 "2012-03-08T04:14:11Z")
Hi Volodymyr Thanks for your helpful response. From what you say, opcode caching is essential and Xcache is the way to go. But just to understand - does a php-fpm pool access a single Xcache, or is there a separate cache set up for each process? I’m trying to get a handle on the memory implications. Thanks for the heads up on uWSGI. But my sysadmin skills are basic (I’m a developer really) and it looks a bit scary. There’s not much info out there, while fastcgi is supported in the php core. For someone who is not a proper sysadmin, is uWSGI, in its present state of development, really a sensible way to go? Posted at Nginx Forum: > **[Re: Can anyone \*really\* explain opcode caching with PHP?](https://forum.nginx.org/read.php?2,223556,223565#msg-223565)** > > Hi folks Thinking of abandoning mod\_php for the wonderful world of nginx, but googling the issue of opcode caching with fastcgi is proving surprisingly confusing: there's a lot of conflicting information out there. My basic question is this: what is... ---
**Author:** ![gcaplan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/8baadc/32.png) [@gcaplan](https://www.ruby-forum.com/u/gcaplan)\ **Post date:** [March 8, 2012, 4:34am UTC](https://www.ruby-forum.com/t/can-anyone-really-explain-opcode-caching-with-php/217637/5 "2012-03-08T04:34:45Z")
> Roberto > > > I am not a big fan of opcode caching > > I’m interested in your reasons for this. My experience with mod\_php is > that I get huge performance improvements with opcode caching (my app > loads a lot of code and libraries). If you don’t use opcode caching, is > there a better way to get the same benefits? Your answer, is my reason 🙂 It is app-dependent, so i never blindly suggest to someone using it, without a proper undestanding of the system. Often i have seen badly configured apache server exposing the cached files to all the users of the system and so on. I see it as a second step in building an infrastructure. Having said that, i prefer having an additional layer (like nginx caching or varnish, as already suggested) in front of the apps. …But you can obviously have opcode and caching both working on the same app 🙂 – Roberto De Ioris > **[unbit - Overview](https://github.com/unbit)** > > makers of uWSGI and many more open source projects - unbit ---
**Author:** ![gcaplan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/8baadc/32.png) [@gcaplan](https://www.ruby-forum.com/u/gcaplan)\ **Post date:** [March 8, 2012, 4:19am UTC](https://www.ruby-forum.com/t/can-anyone-really-explain-opcode-caching-with-php/217637/6 "2012-03-08T04:19:50Z")
Roberto > I am not a big fan of opcode caching I’m interested in your reasons for this. My experience with mod\_php is that I get huge performance improvements with opcode caching (my app loads a lot of code and libraries). If you don’t use opcode caching, is there a better way to get the same benefits? Posted at Nginx Forum: [http://forum.nginx.org/read.php?2,223556,223568#msg-223568](http://forum.nginx.org/read.php?2,223556,223568#msg-223568) ---
**Author:** ![gcaplan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/8baadc/32.png) [@gcaplan](https://www.ruby-forum.com/u/gcaplan)\ **Post date:** [March 8, 2012, 4:36am UTC](https://www.ruby-forum.com/t/can-anyone-really-explain-opcode-caching-with-php/217637/7 "2012-03-08T04:36:00Z")
> Thanks for the heads up on uWSGI. But my sysadmin skills are basic (I’m > a developer really) and it looks a bit scary. There’s not much info out > there, while fastcgi is supported in the php core. For someone who is > not a proper sysadmin, is uWSGI, in its present state of development, > really a sensible way to go? php-fpm (far better that the fastcgi embedded server) is in the core from a couple of php releases (even if not compiled-in by default and somewhere marked as experimental) but you will find tons of users of it. uWSGI got proper php support from a couple of weeks, but it has the advantage in having years of python/perl/lua hosting, so it has a very solid core. Is its php plugin stable ? I would be a fool in saying that after only two weeks, but i suggest you to maintain an eye on it 🙂 – Roberto De Ioris > **[unbit - Overview](https://github.com/unbit)** > > makers of uWSGI and many more open source projects - unbit ---
**Author:** ![gcaplan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/8baadc/32.png) [@gcaplan](https://www.ruby-forum.com/u/gcaplan)\ **Post date:** [March 8, 2012, 8:16am UTC](https://www.ruby-forum.com/t/can-anyone-really-explain-opcode-caching-with-php/217637/8 "2012-03-08T08:16:11Z")
Hi guys You’ve been brilliant - so for now I go with php-fpm and xcache, and I actually understand what’s happening! As I say, the community might consider adding this info to the FAQs, as there’s a lot of misleading blogs and post out there on this whole issue of fastcgi and opcode caching… Thanks for all your help! Posted at Nginx Forum: > **[Re: Can anyone \*really\* explain opcode caching with PHP?](https://forum.nginx.org/read.php?2,223556,223583#msg-223583)** > > Hi folks Thinking of abandoning mod\_php for the wonderful world of nginx, but googling the issue of opcode caching with fastcgi is proving surprisingly confusing: there's a lot of conflicting information out there. My basic question is this: what is...