In today's era, where optimizing the performance of applications is becoming increasingly important, attention must be paid to details that might not seem key at first glance. One such detail in PHP configuration is session.gc_divisor. This article will focus on the importance and practical use of session.gc_divisor for managing sessions in PHP.
What is session.gc_divisor?
session.gc_divisor is a configuration directive in PHP that affects the likelihood of the Garbage Collector (GC) for sessions being triggered. The Garbage Collector is a process that cleans up old and unused session data to free up space and resources on the server.
The PHP session mechanism uses three main directives to control GC:
session.gc_probability: Determines the likelihood that GC will be triggered upon session opening.session.gc_divisor: This directive serves as the denominator in a fraction whose numerator issession.gc_probability.session.gc_maxlifetime: Defines the time after which session data will be considered outdated and thus suitable for cleanup.
The probability of GC being triggered is calculated as follows: Probability of GC triggering=session.gc_probabilitysession.gc_divisorProbability of GC triggering=session.gc_divisorsession.gc_probability
How session.gc_divisor Affects Performance
If the value of session.gc_divisor is set high, it means that GC will be triggered less frequently. This setting may be suitable for high-performance servers with a large amount of memory, where frequent GC is not necessary. On the other hand, for servers with limited resources, a lower session.gc_divisor value may be more appropriate to regularly free up space.
Recommended Values and Practical Settings
The default value of session.gc_divisor in PHP is 100. This number means that if session.gc_probability is also set to 1 (which is the default), GC will be triggered with a probability of 1/100 (1%) for each session.
For high-load servers with robust infrastructure, it may be appropriate to increase this number to reduce the frequency of GC and save resources. Conversely, in environments with smaller servers, it may be useful to reduce session.gc_divisor, for example, to 50, which increases the probability of GC triggering to 2%.
Proper setting of session.gc_divisor is key to maintaining the performance and stability of PHP applications. Many factors must be considered when deciding on the optimal value, including the type of hardware, expected load, and specifics of the application. By experimenting and monitoring performance, the best configuration for a specific environment can be found.
