Home Backend Development PHP Problem How to limit memory usage of PHP process using memory_limit

How to limit memory usage of PHP process using memory_limit

Jun 23, 2021 pm 04:24 PM
php

Memory_limit in virtual host PHP is the maximum available memory limit for a single execution of a single PHP script; the default limit is 256MB, and the maximum can be adjusted to 512MB. The editor below introduces how to use memory_limit to limit the memory usage of the PHP process.

How to limit memory usage of PHP process using memory_limit

memory_limit As the name suggests, it limits the memory usage of the PHP process. For example:

magento2’s system requirements have restrictions on PHP memory_limit, which cannot be lower than 512M. (The default value is 128M. If it is not changed, magento’s background processing logic will not be executed normally)

Look at the explanation on the PHP official website

This sets the maximum amount of memory in bytes that a script is allowed to allocate. This helps prevent poorly written scripts for eating up all available memory on a server. Note that to have no memory limit, set this directive to -1.

Required Note that the higher the value of memory_limit, that is, the more memory a single PHP process takes up, the fewer requests the system can handle concurrently. For example, if a machine with 2G memory

memory_limit is set to 128M, it can handle up to 16 requests at the same time. If memory_limit is set to 256M, it can handle up to 8 requests at the same time. If memory_limit is set to 512M, it can handle up to 4 requests at the same time. Request

Is the larger the value of memory_limit, the better?

Of course not, memory_limit is mainly to prevent program bugs or infinite loops from occupying a large amount of memory, causing system downtime. When introducing a large number of third-party plug-ins or codes, it is very necessary to limit memory.

Memory_limit will make each PHP process occupy a fixed amount of memory?

Or is it just the upper limit of allocated memory? Test the

idea, set memory_limit to 10M, initialize a 2M/20M string in the PHP request, and see the memory usage in the system process.

Nginx configuration

server {
        listen 8093;
        root /home/zhongwei/work/test/memory_limit/;
        index index.php index.html index.htm;
        server_name localhost;
        location / {
                # try_files $uri $uri/ =404;
                try_files $uri $uri/ /index.php?q=$uri&$args;
        }
        location ~ \.php$ {
include snippets/fastcgi-php.conf;
fastcgi_param PHP_VALUE "memory_limit = 10M";
fastcgi_pass unix:/run/php/php7.0-fpm.sock;
        }
}
Copy after login

PHP test file

<?php
$char_count = 2;
$M = 1024 * 1024;
echo sprintf("Current memory_limit value is: %s.", ini_get(&#39;memory_limit&#39;));
echo sprintf(&#39;<br/>Amount of memory allocated to PHP: %0.3fM.&#39;, memory_get_usage() / $M);
$s = str_repeat("a", $M * $char_count);
//sleep(30);
echo sprintf(&#39;<br/>Amount of memory allocated to PHP: %0.3fM.&#39;, memory_get_usage() / $M);
echo sprintf(&#39;<br/>Total memory allocated from system: %0.3fM.&#39;, memory_get_usage($real_usage=true) / $M);
echo &#39;<br/>success&#39;;
Copy after login

Test result

When $char_count is 2, a string occupying 2M of memory is initialized and output The result is

Current memory_limit value is: 10M.
Amount of memory allocated to PHP: 0.344M.
Amount of memory allocated to PHP: 2.348M.
Total memory allocated from system: 4.004M.
success
Copy after login

$char_count is 20, that is, a string occupying 20M of memory is initialized, and the output result is

Current memory_limit value is: 10M.
Amount of memory allocated to PHP: 0.346M.
Copy after login

Note that the HTTP status code is 500, which means that the string is executed During initialization, the PHP process was killed by the system.

Look at the log information recorded in Nginx error.log

2017/03/01 10:41:23 [error] 6903#6903: *39 FastCGI sent in stderr: "PHP message: PHP Fatal error:  Allowed memory size of 10485760 bytes exhausted (tried to allocate 20971552 bytes) in /home/zhongwei/work/test/memory_limit/index.php on line 8
PHP message: PHP Stack trace:
PHP message: PHP   1. {main}() /home/zhongwei/work/test/memory_limit/index.php:0
PHP message: PHP   2. str_repeat() /home/zhongwei/work/test/memory_limit/index.php:8" while reading response header from upstream, client: 127.0.0.1, server: localhost, request: "GET / HTTP/1.1", upstream: "fastcgi://unix:/run/php/php7.0-fpm.sock:", host: "localhost:8093"
Copy after login

The actual test results show that memory_limit only limits the upper limit of memory usage for each PHP process, rather than allocating it to each process. Fixed memory. Therefore, the number of concurrency will not decrease because the memory_limit setting is larger.

What is the default value of memory_limit

  • Before PHP 5.2 it was 8M

  • PHP 5.2 is 16M

  • The version after PHP 5.2 is 128M

Recommended learning: php video tutorial

The above is the detailed content of How to limit memory usage of PHP process using memory_limit. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian Dec 24, 2024 pm 04:42 PM

PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals. This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati

7 PHP Functions I Regret I Didn't Know Before 7 PHP Functions I Regret I Didn't Know Before Nov 13, 2024 am 09:42 AM

If you are an experienced PHP developer, you might have the feeling that you’ve been there and done that already.You have developed a significant number of applications, debugged millions of lines of code, and tweaked a bunch of scripts to achieve op

How To Set Up Visual Studio Code (VS Code) for PHP Development How To Set Up Visual Studio Code (VS Code) for PHP Development Dec 20, 2024 am 11:31 AM

Visual Studio Code, also known as VS Code, is a free source code editor — or integrated development environment (IDE) — available for all major operating systems. With a large collection of extensions for many programming languages, VS Code can be c

Explain JSON Web Tokens (JWT) and their use case in PHP APIs. Explain JSON Web Tokens (JWT) and their use case in PHP APIs. Apr 05, 2025 am 12:04 AM

JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,

How do you parse and process HTML/XML in PHP? How do you parse and process HTML/XML in PHP? Feb 07, 2025 am 11:57 AM

This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an

PHP Program to Count Vowels in a String PHP Program to Count Vowels in a String Feb 07, 2025 pm 12:12 PM

A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total

Explain late static binding in PHP (static::). Explain late static binding in PHP (static::). Apr 03, 2025 am 12:04 AM

Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.

What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases? What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases? Apr 03, 2025 am 12:03 AM

What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.

See all articles