Linux kernel parameter

Overview

Linux kernel parameter에 대한 기술 문서입니다.

Summary

• 무엇인가? - Linux kernel parameter
• 왜 필요한가? - HPC 및 서버 환경에서 필수 개념
• 언제 사용하는가? - 서버 구성, 성능 튜닝, 문제 해결 시

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Purpose

이 문서가 존재하는 이유

• Goal: Linux kernel parameter에 대한 기술 정보 제공
• Scope: Linux kernel parameter의 개념, 사용법, 설정
• Non-goals: 다른 주제로의 확장

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Key Concepts

Concept	Description	Related
Linux kernel parameter	HPC/서버 환경에서 중요한 기술 개념	Linux, Server

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Detailed Explanation

• Kernel

sysctl can be used to modify kernel parameters at runtime without recompiling the entire kernel. can help in faster release of network resources.After adjusting the TCP FIN Timeout:

sudo sysctl -w net.ipv4.tcp_fin_timeout=30

determines the time interval for TCP keepalive packets

sudo sysctl -w net.ipv4.tcp_keepalive_time=120

Enable the TCP selective acks option for better throughput:

# sysctl -w net.ipv4.tcp_sack=1

Disable the TCP timestamps option for better CPU utilization

# sysctl -w net.ipv4.tcp_timestamps=0

somaxconn is used to set the maximum number of connections that can be queued for a socket. This parameter is used to prevent a flood of connection requests from overwhelming the system. The maximum value for the net.core.somaxconn parameter depends on the system and kernel version. The default value for the net.core.somaxconn Linux kernel parameter is typically 128 and the maximum value is around 65535 on most systems. It is important to set the net.core.somaxconn parameter to a value that is larger than the backlog value of NGINX, as the backlog value is used to determine the maximum number of connections that can be queued for a listening socket of NGINX only. If the net.core.somaxconn value is smaller than the backlog value, NGINX will not be able to queue all the incoming connections, resulting in connection errors. For example, if your average queue length from vmstat is 1000 and you have 2 CPU cores,

the optimal value for net.core.somaxconn would be 1000 * 4 / 2 = 2000.

The formula for net.core.somaxconn 
optimal value = CPU cores * queue length / 4

can optimize how the kernel handles file system caches

sudo sysctl -w vm.vfs_cache_pressure=50

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Best Practices

• 최신 버전 사용 권장
• 공식 문서 참고
• 테스트 환경에서 먼저 검증

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References

• Linux kernel parameter

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Related Pages

• Linux
• Server
• Hardware
• Network

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Knowledge Graph

Related

→ Linux Kernel Tuning → THP (Transparent Huge Pages) → systemd → Kernel tips and tricks → LVM → iptables → Ubuntu → Kernel boot param