Magento is a extremely flexible ecommerce framework, but that flexibility comes with a price: performance. This answer is a collection of pointers and some details on caching (especially for blocks).
One thing to consider is the Magento environment, e.g. tuning the php, the web server (favor nginx over Apache), and MySQL. Also, set up a good caching backend for Magento. All these are covered e.g. in the Magento Performance Whitepaper that applies also to the CE.
After the environment is set up, the other side of things is the code.
Reducing the number of queries is possible for some pages by enabling the flat table catalog (System > Configuration > Catalog > Frontend), but you will always have a high number of queries.
You also can't really reduce the time spent creating the blocks except by tuning the environment (APC, memory, CPU). So as the other commenters said, your best choice is utilizing the caching functionality that Magento has built in.
Magento Block Caching
Because you specifically mentioned blocks in the question, I'll elaborate a bit more on block caching. Block caching is governed by three properties:
- cache_lifetime
- cache_key
- cache_tags
All these properties can be set in the _construct() method of a block using setData() or magic setters, or by implementing the associated getter methods (getCacheLifetime(), getCacheKey(), getCacheTags()).
The cache_lifetime is specified in (integer) seconds. If it is set to false(boolean), the block will be cached for ever (no expiry). If it is set to nullthe block will not be cached (this is the default in Mage_Core_Block_Abstract).
The cache_key is the unique string that is used to identify the cache record in the cache pool. By default it is constructed from the array returned by the method getCacheKeyInfo().
// Mage_Core_Block_Abstract
public function getCacheKeyInfo()
{
return array(
$this->getNameInLayout()
);
}
public function getCacheKey()
{
if ($this->hasData('cache_key')) {
return $this->getData('cache_key');
}
/**
* don't prevent recalculation by saving generated cache key
* because of ability to render single block instance with different data
*/
$key = $this->getCacheKeyInfo();
//ksort($key); // ignore order
$key = array_values($key); // ignore array keys
$key = implode('|', $key);
$key = sha1($key);
return $key;
}
The best way to customize the cache key in custom blocks is to override the getCacheKeyInfo() method and add the data that you need to uniquely identify the cached block as needed.
For example, in order to cache a different version of a block depending on the customer group you could do:
public function getCacheKeyInfo()
{
$info = parent::getCacheKeyInfo();
$info[] = Mage::getSingleton('customer/session')->getCustomerGroupId()
return $info;
}
The cache_tags are an array that enable cache segmentation. You can delete sections of the cache matching one or more tags only.
In the admin interface under System > Cache Management you can see a couple of the default cache tags that are available (e.g. BLOCK_HTML, CONFIG, ...). You can use custom cache tags, too, simply by specifying them.
This is part of the Zend_Cache implementation, and needs to be customized far less frequently compared to the cache_lifetime and the cache_key.
Other Caching
Besides blocks Magento caches many other things (collection data, configuration, ...).
You can cache your own data using Mage::app()->saveCache(), Mage::app()->loadCache(), Mage::app()->cleanCache() and Mage::app()->removeCache(). Please look in Mage_Core_Model_App for details on these methods, they are rather straight forward.
You will also want to use a full page cache module. If you are using the Magento EE, you already have one. Otherwise search Magento Connect - there are many options (commercial).
Some of those modules also tune various parts of Magento for you beyond the full page caching aspect, e.g. Nitrogento (commercial).
Using a reverse proxy like Varnish is also very beneficial.
There are quite a number of blog posts on this subject. Here is one post by the publishers of the Nitrogento extension.
If you are running Magento on a more low-scale environment, check out my post on the optimization of the file cache backend on magebase.com.
Best Answer
Here is a method of updating the config cache rather than clearing it, thus avoiding race-conditions.
https://gist.github.com/2715268