Re: [PHP] XCache, APC, Memcached... confused
First of all you need to get it clear in your head what an opcode cache is actually doing. It does not cache the website, it caches the compiled version of the PHP scripts such that PHP doesn't need to recompile each file every time it's included which is the default way PHP works. And, to be really clear, the savings in compile time is gravy. The REAL savings is not hitting that slow-spinning disk drive to LOAD the PHP script into RAM. You'd get very similar performance boost if the opcode cache simply cached the PHP source. But it's just as easy to cache the compiled version, and that saves a few more microseconds/milliseconds. Depends how big/long/convoluted the PHP source is, but, really, it rarely is that big of a file. I doubt that 2 opcode caches can run in parallel, as they both hook into the same line of code in PHP. And if they did run in parallel, the second one would not help in the least, and would actually just be more overhead for zero gain. PS All the opcode caches have a strategy for unloading less-used scripts if RAM is full, so don't sweat it unless you have crazy number of scripts. -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
[PHP] XCache, APC, Memcached... confused
Hi, I became confused after an hour trying to understand the PHP cache solutions. XCache, APC, eAccelerator and others are opcode cache systems... is memcache in the same category? or is it completely different? If I install for example XCache, set it for certain directory... it will automatically cache the website into the memory. What happens if the memory will get full? Thanks for explanation, Martin -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] XCache, APC, Memcached... confused
On 22 Oct 2008, at 22:19, Martin Zvarík wrote: I became confused after an hour trying to understand the PHP cache solutions. XCache, APC, eAccelerator and others are opcode cache systems... is memcache in the same category? or is it completely different? Memcache is completely different in that it's not an opcode cache, it's an in-memory volatile cache for arbitrary key = value data with a client-server API. If I install for example XCache, set it for certain directory... it will automatically cache the website into the memory. What happens if the memory will get full? First of all you need to get it clear in your head what an opcode cache is actually doing. It does not cache the website, it caches the compiled version of the PHP scripts such that PHP doesn't need to recompile each file every time it's included which is the default way PHP works. Secondly, if you run out of memory you buy more!! But seriously, you'd need a very very very big site to have this problem. An opcode cache of a PHP script will generally take less space than the script itself. So if you're worried about it simply get the total size of all the PHP scripts in your site and you'll see that even on modest hardware you'll have a lot of headroom. Obviously you need to take other users of the server into account, especially if you're on a shared hosting account, but in most cases you won't have a problem. -Stut -- http://stut.net/ -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] XCache, APC, Memcached... confused
Thanks for reply Stut. So, the APC, XCache etc. doesn't work as FileCache and also doesn't decrease the number of database queries, since it is not caching the content... I see now, it is obvious that it would be very hard to run out of memory. -- Martin Stut napsal(a): On 22 Oct 2008, at 22:19, Martin Zvarík wrote: I became confused after an hour trying to understand the PHP cache solutions. XCache, APC, eAccelerator and others are opcode cache systems... is memcache in the same category? or is it completely different? Memcache is completely different in that it's not an opcode cache, it's an in-memory volatile cache for arbitrary key = value data with a client-server API. If I install for example XCache, set it for certain directory... it will automatically cache the website into the memory. What happens if the memory will get full? First of all you need to get it clear in your head what an opcode cache is actually doing. It does not cache the website, it caches the compiled version of the PHP scripts such that PHP doesn't need to recompile each file every time it's included which is the default way PHP works. Secondly, if you run out of memory you buy more!! But seriously, you'd need a very very very big site to have this problem. An opcode cache of a PHP script will generally take less space than the script itself. So if you're worried about it simply get the total size of all the PHP scripts in your site and you'll see that even on modest hardware you'll have a lot of headroom. Obviously you need to take other users of the server into account, especially if you're on a shared hosting account, but in most cases you won't have a problem. -Stut -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] XCache, APC, Memcached... confused
I am looking at the eAccelerator's website and I realize what got me confused: there is a function for OUTPUT CACHE, so it actually could cache the whole website and then run out of memory I guess... that means I would be able to store anything into the memory and reference it by a variable? are the variables accessible across the whole server? I still don't really understand, but I am trying... Stut napsal(a): On 22 Oct 2008, at 22:19, Martin Zvarík wrote: I became confused after an hour trying to understand the PHP cache solutions. XCache, APC, eAccelerator and others are opcode cache systems... is memcache in the same category? or is it completely different? Memcache is completely different in that it's not an opcode cache, it's an in-memory volatile cache for arbitrary key = value data with a client-server API. If I install for example XCache, set it for certain directory... it will automatically cache the website into the memory. What happens if the memory will get full? First of all you need to get it clear in your head what an opcode cache is actually doing. It does not cache the website, it caches the compiled version of the PHP scripts such that PHP doesn't need to recompile each file every time it's included which is the default way PHP works. Secondly, if you run out of memory you buy more!! But seriously, you'd need a very very very big site to have this problem. An opcode cache of a PHP script will generally take less space than the script itself. So if you're worried about it simply get the total size of all the PHP scripts in your site and you'll see that even on modest hardware you'll have a lot of headroom. Obviously you need to take other users of the server into account, especially if you're on a shared hosting account, but in most cases you won't have a problem. -Stut -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] XCache, APC, Memcached... confused
On 23 Oct 2008, at 00:04, Martin Zvarík wrote: I am looking at the eAccelerator's website and I realize what got me confused: there is a function for OUTPUT CACHE, so it actually could cache the whole website and then run out of memory I guess... that means I would be able to store anything into the memory and reference it by a variable? are the variables accessible across the whole server? I still don't really understand, but I am trying... Having never used eAccelerator I can only guess, but it sounds like it's a way to cache HTML output. As for how accessible that is I have no idea. I suggest you find the eAccelerator mailing list, subscribe to that and ask your question there. -Stut -- http://stut.net/ Stut napsal(a): On 22 Oct 2008, at 22:19, Martin Zvarík wrote: I became confused after an hour trying to understand the PHP cache solutions. XCache, APC, eAccelerator and others are opcode cache systems... is memcache in the same category? or is it completely different? Memcache is completely different in that it's not an opcode cache, it's an in-memory volatile cache for arbitrary key = value data with a client-server API. If I install for example XCache, set it for certain directory... it will automatically cache the website into the memory. What happens if the memory will get full? First of all you need to get it clear in your head what an opcode cache is actually doing. It does not cache the website, it caches the compiled version of the PHP scripts such that PHP doesn't need to recompile each file every time it's included which is the default way PHP works. Secondly, if you run out of memory you buy more!! But seriously, you'd need a very very very big site to have this problem. An opcode cache of a PHP script will generally take less space than the script itself. So if you're worried about it simply get the total size of all the PHP scripts in your site and you'll see that even on modest hardware you'll have a lot of headroom. Obviously you need to take other users of the server into account, especially if you're on a shared hosting account, but in most cases you won't have a problem. -Stut -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
