started performance section of the guide

docs/guide/performance.md

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+Performance Tuning
+==================
+
+Application performance consists of two parts. First is the framework performance
+and the second is the application itself. Yii has a pretty low performance impact
+on your application out of the box and can be fine-tuned further for production
+environment. As for the application, we'll provide some of the best practices
+along with examples on how to apply them to Yii.
+
+Preparing framework for production
+----------------------------------
+
+### Disabling Debug Mode
+
+First thing you should do before deploying your application to production environment
+is to disable debug mode. A Yii application runs in debug mode if the constant
+`YII_DEBUG` is defined as `true` in `index.php`. Debug mode is useful during
+development stage, but it would impact performance because some components
+cause extra burden in debug mode. For example, the message logger may record
+additional debug information for every message being logged.
+
+### Enabling PHP opcode cache
+
+Enabling the PHP opcode cache improves any PHP application performance and lowers
+memory usage. Yii is no exception. It was tested with APC extension that caches
+and optimizes PHP intermediate code and avoids the time spent in parsing PHP
+scripts for every incoming request.
+
+### Turning on ActiveRecord database schema caching
+
+If the application is using Active Record, we should turn on the schema caching
+to save the time of parsing database schema. This can be done by setting the
+`Connection::enableSchemaCache` property to be `true` via application configuration
+`protected/config/main.php`:
+
+```php
+
+```
+
+### Combining and Minimizing Assets
+
+
+### Using better storage for sessions
+
+By default PHP uses plain files to handle sessions. It is OK for development and
+small projects but when it comes to handling concurrent requests it's better to
+switch to another storage such as database. You can do so by configuring your
+application via `protected/config/main.php`:
+
+
+```php
+```
+
+
+Improving application
+---------------------
+
+### Using Caching Techniques
+
+As described in the Caching section, Yii provides several caching solutions that
+may improve the performance of a Web application significantly. If the generation
+of some data takes long time, we can use the data caching approach to reduce the
+data generation frequency; If a portion of page remains relatively static, we
+can use the fragment caching approach to reduce its rendering frequency;
+If a whole page remains relative static, we can use the page caching approach to
+save the rendering cost for the whole page.
+
+
+### Database Optimization
+
+Fetching data from database is often the main performance bottleneck in
+a Web application. Although using caching may alleviate the performance hit,
+it does not fully solve the problem. When the database contains enormous data
+and the cached data is invalid, fetching the latest data could be prohibitively
+expensive without proper database and query design.
+
+Design index wisely in a database. Indexing can make SELECT queries much faster,
+but it may slow down INSERT, UPDATE or DELETE queries.
+
+For complex queries, it is recommended to create a database view for it instead
+of issuing the queries inside the PHP code and asking DBMS to parse them repetitively.
+
+Do not overuse Active Record. Although Active Record is good at modelling data
+in an OOP fashion, it actually degrades performance due to the fact that it needs
+to create one or several objects to represent each row of query result. For data
+intensive applications, using DAO or database APIs at lower level could be
+a better choice.
+
+Last but not least, use LIMIT in your SELECT queries. This avoids fetching
+overwhelming data from database and exhausting the memory allocated to PHP.
+
+### Using asArray
+
+### Processing data in background
+
+In order to respond to user requests faster you can process heavy parts of the
+request later if there's no need for immediate response.
+
+- Cron jobs + console.
+- queues + handlers.

docs/guide/template.md

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+Template
+========
+