How voracious is magento?

Question

PHP

Actually, at work, I came across a client site on magento. Attendance is zero (i.e. the site has just been made and there are no visitors there yet).
The site was wildly stupid on the hosting, from the moment the request was sent to the moment the download started, 5-10 seconds passed.
Moved to VPS(OpenVZ 1024M Ram, 2 core=2.4GHz), upgraded apache+php+mysql+memcached+apc, enabled internal magento cache.
As a result, the page starts to give in 1-3 seconds, and not in 5-10.
At the same time, httpd loads the percentage by 120% during these same 1-3 seconds.
Question: this is the normal behavior of magento and I under-optimized something, or most likely the developer added some wildly crooked module of his own and it generates all this load.

Answer 1

Try to turn on profiling - then you can find an approximate bottleneck.
in index.php uncomment #Varien_Profiler::enable();
and in the admin panel system->configuration->developer->debug
+enable logging.
magento - not ideal in terms of performance - but not so much that it would load up to 10 seconds, even up to 3 - that's a lot.
Most likely there are third-party modules or just pieces of code that are inserted into templates - which make such a high load.

Answer 2

Try enabling compilation in Magento settings.
It greatly improves performance in some cases.

Answer 3

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addition from 2014-05-19:
One of the ways to speed up by 30 % of any store on Magento is my second (after the Russian assembly of Magento) software product " Fast Core Magento ".
" Fast Magento Core " is a C-based PHP extension (an additional "module" for the PHP interpreter) that replaces some of Magento's most resource-intensive programming areas (functions) with an identical in functionality, but an order of magnitude faster implementation of them in C.
"Fast Magento Core" is compatible with all editions of Magento: Magento Russian Assembly, Magento Community Edition, Magento Enterprise Edition.
"Fast Magento Core" is a tool that is recommended to be used in combination with other ways to speed up Magento: for example, " Full Page Caching " and " Block Caching " modules of Magento Russian Build.
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1. For a full-fledged industrial operation of an online store on Magento, a virtual server with 1 GB of RAM is not enough . I recommend and set up dedicated (non-virtual) servers with 32 gigabytes of RAM for
   free for Magento Russian assembly clients .
   
2. To operate an online store on Magento, the Apache web server is redundant : the online store will run faster if you use and properly configure the nginx web server .
   The functionality of nginx is quite enough for Magento.
   
3. When an online store works on only one physical server, then installing memcached is meaningless (after all, memcached is designed for distributed caching of data between several servers), it is enough to use and configure APC correctly .
   
4. To speed up Magento, it is important to purchase and set up a full-page caching module .
   This module is not included in the free version of Magento Community Edition, but it is present in the standard package of professional editions of Magento: Enterprise Edition and the Russian assembly of Magento.
   
5. To speed up Magento, it is important to use Magento's built-in compiler .
   The compiler combines files with source code (and there are thousands of them in Magento) into several (3-5) large files, which significantly speeds up the system (fewer file accesses, and these large files, if the server is properly configured, will be cached as bytecode via APC) .

Answer 4

Moved to VPS(OpenVZ 1024M Ram, 2 core=2.4GHz), upgraded apache+php+mysql+memcached+apc, enabled internal magento cache.

1024M is certainly not enough for production, but it is quite enough for a test run.
The problem is most likely in the modules. and craftsmen who developed the site.
Turn on the profiler, it will show what exactly is slowing down.