Even tho the website is behind CloudFlare CDN, we decided to use OPCache to reduce the load on server as there are a maximum (peak) of ~400 active users per second (most of the time it's 50-100 u/s).
But most pages have some different data for each user, for example user's dashboard overview, most of the data is same but it has some different numbers for each user that needs to be up to date.
My Questions are:
Is it wise to use OPCache for such a website?
How will it handle pages with unique queries? will it take more RAM (caching multiple pages for each user) than running without OPCache?
Will it affect performance on pages such as Signup/Login etc?
I read that all PHP applications should use OPCache, is that correct?
P.S. The website is running on PHP 7.3.4
Yes it will gain performance improvement
If your RAM usage increased and you're concerned with it, you can fine tune memory consumption via opcache.memory_consumption
Affect meaning they will be faster
Yes, there really is no reason to not use OPCache other than edge cases (e.g., when your app's source code changes at a very fast rate or testing).
TLDR: Production code should always have OPCached enabled.
OPcache only caches the internal opcode representation of a PHP script, not its output. The queries performed or the content displayed by the page has no impact on how OPcache will behave.
This caching will improve the performance of all PHP web pages. As such, it should always be enabled on production sites.
Each PHP script is being compiled at runtime,
It takes time to transform the human readable code into a code that can be understood by the machine.
OpCache is a bytecode cache engine , it will compile the script to bytecode script only once - so you will save time - then the precompiled script is being stored in memory, which should lead to performance boosts in your PHP applications.
What i think you are missing is that the opcache DOES NOT cache the result of the script , but it is just compile the script .
Note this method is not good if the php script it self is changing for each user
or if it is loaded from -let's say for example- a database
As general view for this approach
Php caching whatever it was APC cache or opcache or else is amazing strategy this should increase php performance by 50% in general
As it act as follows
When php script excuted there's this involve three major steps
1-parse of the script
2-compile of the script
3-output
APC cache or else act as intermediary as it saves php script in the compiled form so php will start in the output stage directly and this will not affect queries but it will increase its speed as query for MySQL or else not just the statement of SELECT or whatever but it involves execution of extensions like PDO so it will become faster
You can classify extension as follows
APC or Xcache for php 5
In new php version use opcache
All of them have the same principle
Some developers like APC other like opcache
As example X-cart the popular shopping platform use xcache .
Related
I just recently got an updated about Opcache in php and i am little familiar with file based caching in Codeigniter.
But i thought as of now File based caching is faster other caching techniques, since there won't be any database access and it directly connect to the generated html file to load. So it should be fast than other techniques.
So i have searched in Google and some websites compared the speed of caching by benchmarking it where they mentioned File caching is slow on retrieve when compared to other caching technique memcache and Opcache php and I am confused with the report.
I know every caching technique having their own pros and cons. Suggest me on the situation so my page won't be need of real time data and currently i am using file based caching. So Is it ok to go Opcache or Memache?
Opcache and Memcached store data in memory. In the vast majority of cases, retrieving data from memory is faster than retrieving data from the file system. The drawback? Running Memcached and using an opcache will obviously use up some of your server's memory.
OPcache improves PHP performance by storing precompiled script bytecode in shared memory, thereby removing the need for PHP to load and parse scripts on each request.
File based caching that you are talking about is about caching your variable to a file and get it on later. (often use when the time for getting data is very slow)
Therefore, you can still use file based caching to store your variable and use Opcache for caching your script. However, to cache your data to memory will be much more faster. In that case, try Memcached/Redis or anything you can find.
I'm just wondering is it stupid to use both Xcache 3 with Zend Opcache at the same time to cache PHP files? I know that both do almost the same job, but not sure if that would make any difference on the performance and speed.
I want to speed up my php page load so that visitors don't need to wait long.
any thoughts on that?
To answer your question: Yes, you should not run xcache and Zend Opcache at the same time. If you do, you'll get undefined behaviours, most notably "cannot redeclare class XYZ" fatal errors. That happened to me after a systems upgrade, where the packet maintainer activated Zend Opcache along the already existing xcache installation.
As for the matter of which of both to use for opcaching, that depends on your specific code - I'd recommend setting up a test environment and firing up the Apache Benchmark or a similar tool to check the answer times.
On a default wordpress installation, I was able to get a speedup (uncached vs xcache) of about 5-7x, which is quite significant. If you really need more, you'll need to check out the other possibilities already mentioned in the comments like
using a loadbalancer and multiple application servers
using memcache or memcached to cache database queries and other load heavy operations
switching to another database system like a NoSQL system (be careful of the consequences)
changing your architecture to a static site with webservices providing interactive content
I've searched all over the web for documentation including on the XCache website.
I'm new to PHP opcode caching and XCache. I'd like an explanation of how XCache works. I know that it stores compiled php code so that it doesn't need to be recompiled everytime. But how does XCache know when php code has been updated and thus the cache is out of date?
How do I know if I need to clear the cache?
Does XCache compile and cache all php code on the server? If so can this be configured?
What are clogs? OOMs? I see large numbers for both of these in the XCache Admin page interface.
In the Code Coverage Viewer... what does Percent mean? Is this the percentage of code that has been cached?
Does hits mean the number of lines of compiled code that has been read from cache?
Does lines mean the total number of lines of code?
What is the ToDo column for?
Why are some lines highlighted in red?
I'm using PHP 5.3.2, XCache 1.3.0, and Ubuntu 10.04 if it helps.
Xcache:
optimizes performance by removing the compilation time of PHP scripts
by caching the compiled state of PHP scripts into the shm (RAM) and
uses the compiled version straight from the RAM.
Based on observations using PHP 5.5.3 and Xcache 3.1.0 this is what I can deduce:
Cacher
This module deals with two kinds of caching Opcode and Variable.
The Opcode caching is designed to be a simple drop-in. You can't customize how it decides to cache, just how much:
xcache.count setting refers to how many cache threads and correlates to how many processor cores you want to utilize — the idea is that multithreading should be the fastest, but there is no guarantee so experiment yourself
As a guideline, valid count values would be 2^n like 1, 2, 4, 8 — 0 will disable the cacher and other values will get rounded to the nearest valid value
xcache.size setting refers to the aggregate memory of all cache threads. So, each thread gets roughly size/count amount of memory
OOM aka Out of Memory, refers to the event of a cache thread hitting it's maximum size
Variable caching requires using a simple get/set api in your app code. After enabling it using xcache.var_size and xcache.var_count (similar to Opcode settings) you use xcache_set($var1) and xcache_get($var1) in your scripts.
Invalidation
The xcache.stat setting controls whether or not to check if the file was modified since it was cached:
When set to On files get checked and re-cached
When set to Off skips the check will keep the first cached version as long as the expiration time, which could help performance by limiting disk i/o
In your dev environment it's a good idea to keep it On so you can update and check your code continuously — otherwise you have to flush the cache to see updates to files.
Flushing
There is a web admin interface which allows you to flush a particular cache. The web admin uses a php api: xcache_clear_cache(…).
Since the cache is RAM based anytime the server restarts the cache should be flushed.
Expiration
Cached items expire according to xcache.ttl and xcache.var_ttl which respectively control the number of seconds a cached item lives (0 is indefinite and the default).
Coverager
The coverager module, aka Code Coverage, is a little mysterious. According to the FeatureList it seems like a diagnostic tool intended to be enabled for temporary administrative/testing situations:
Coverager + real life testcase framework, this include: [TOSHARE]
real life testcase framework, a control script with real browser. you have to write the test cases.
builtin Coverager + its viewer from web, to see how much script you have tested.
the testcase+Coverager just help you make sure all real life php web applications is running correctly when
after enabling XCache
after upgrading php4 to php5
after upgrading php4/5 to php6
A friend has recommended that I install php APC, claiming it will help php run faster and use less memory
sounds promising but I'm a little nervous about adding it to my VPS server
I have one small app that I've built using codeigniter, and several sites that use the popular slideshowpro photo gallery software
could install this break any of the back end code on my sites?
I'm no high tech server guy, but should I give this a try?
Depends entirely on your situation.
Is your site unresponsive or slow at the moment? Is this definitely due to the PHP scripts and not any other data sources such as a database or remote API?
If you answered yes to the above, then installing one of the many PHP accelerators out there would be a good shout. As for using less memory, that's largely dependent on your apache/lightppd/nginx config and php.ini variables.
Most PHP accelerators work by converting the (to be) interpreted PHP code into opcode. This is then stored in memory (RAM) for fast access. If you haven't already implemented file-based caching in CodeIgniter then the benefits of installing a PHP accelerator would be noticeable. If you haven't, then I suggest you do that first before moving straight over to (wasting?) spending time trying to install APC manually.
If your site is currently performing well and you're not too confident in your *nix skills then I suggest you try implementing CodeIgniter caching first rather than try messing with what is an already working VPS.
My personal preference is PHP eAccelerator.
Should installing a PHP cache engine not improve your site's performance then I suggest you look at what other factors influence your application. As stated above, these could be: database or API to name a few.
Hope this helps.
APC is basically a cache engine that stores your compiled php scripts on a temp location on your server. Meaning that these do not have to be interpreted every time someone calls your sccript. It is a PHP extension can can safely be turned ON or OFF and it does not affect your actual code. So... do not fear!
When a php script is processed, there is a compilation phase, where php converts the source code of the php files into "opcodes". APC simply caches the result of this compilation phase, so it should be safe to turn on.
That said, when making such changes to production code it is always wise to run a regression test to ensure no new issues have been introduced.
Does anybody have experience working with PHP accelerators such as MMCache or Zend Accelerator? I'd like to know if using either of these makes PHP comparable to faster web-technologies. Also, are there trade offs for using these?
Note that Zend Optimizer and MMCache (or similar applications) are totally different things. While Zend Optimizer tries to optimize the program opcode MMCache will cache the scripts in memory and reuse the precompiled code.
I did some benchmarks some time ago and you can find the results in my blog (in German though). The basic results:
Zend Optimizer alone didn't help at all. Actually my scripts were slower than without optimizer.
When it comes to caches:
* fastest: eAccelerator
* XCache
* APC
And: You DO want to install a opcode cache!
For example:
alt text http://blogs.interdose.com/dominik/wp-content/uploads/2008/04/opcode_wordpress.png
This is the duration it took to call the wordpress homepage 10.000 times.
Edit: BTW, eAccelerator contains an optimizer itself.
MMCache has been deprecated. I recommend either http://pecl.php.net/package/APC or http://xcache.lighttpd.net/, both of which also give you variable storage (like Memcache).
Both are interesting and will provide speed boost since they compile source code into binary representation which is then executed by the PHP engine.
Any huge web site running with PHP (Facebook for example) is running some sort of opcode cache system like MMCache.
The problem is that they are not very easy to set up depending on your system.
Depending on how much of your PHP code is actually executed and how long that execution takes they can be a really big win. It certainly isn't going to hurt, but the gain you see will very much depend on where your time is currently spent.
btw mmcache has been rolled into a different project now, I forget the name but Google will tell you.
I use APC on my production servers and it works pretty well out of the box. Compile it and add it to PHP and there isn't much tweaking left to do for it. I check it every once in a while just to review stats but since I use MVC a lot all of the main files (routers, controllers, etc) rarely change on a day-to-day basis so that code stays compiled and runs pretty efficiently.
currently we use apc, free and was just a simple plug and play on our live servers. Provided a huge performance increase for our site, especially as the project size increased. I also have the apc.stat disabled so it doesn't check if the code has been updated, so whenever we need to update the code on the live site we restart apache.
I use APC, and can attest that it can dramatically reduce the CPU and I/O load on an app server if you maintain a high cache-hit rate. It not only saves you from having to compile, it can save you from having to read the php files from disk at all. (i.e. the bytecodes are served directly from main memory, so it's super fast) It lowers the speed to render a single page, and increases the requests per second your server can handle.
If you use RedHat or CentOS, installing APC is super simple:
yum install php-devel httpd-devel php-pear
pecl install apc
echo "extension=apc.so" > /etc/php.d/apc.ini
# if you're using SELinux:
chcon "system_u:object_r:textrel_shlib_t" /usr/lib/php/modules/apc.so
/etc/init.d/httpd restart
You asked about downsides. The only downside is that it requires some memory. The default on APC is 30MB, but it can be adjusted, and the cost of a little bit of memory more than pays for itself with the increased speed and response rate.
BlaM's testing included all the DB calls made by WordPress. When you're making fewer DB calls, you'll see the performance gain of opcode caches be even more dramatic.
I used Zend Accelerator a little back in the day (2004-ish). It certainly gave some significant performance wins on code it could work with, but unfortunately the system I was using was designed to quite often dynamically load code and then eval it, which Zend Accelerator couldn't do much with at the time (and I'd guess still can't).
On the down side, we certainly saw some caching issues (where the code would be changes, but the compiled version sync with the change for one reason or another). I imagine those problems have likely been ironed out by now.
Anyway, I don't have any hard comparison numbers, and certainly didn't write the same system in different environments for comparison, but for the vast majority of systems, PHP isn't going to kill you performance wise.
Have you checked out Phalanger? It compiles PHP to .NET code. Here are some benchmarks which show that it can dramatically improve performance.