Linux Process

Overview

Linux Process에 대한 기술 문서입니다.

Summary

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

Purpose

이 문서가 존재하는 이유

• Goal: Linux Process에 대한 기술 정보 제공
• Scope: Linux Process의 개념, 사용법, 설정
• Non-goals: 다른 주제로의 확장

Key Concepts

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

Detailed Explanation

• Linux

S Interruptible sleep (waiting for an event to complete)
D Uninterruptible sleep (usually IO)
R Running or runnable (on run queue)
T Stopped, either by a job control signal or because it is being traced.
W paging (not valid since the 2.6.xx kernel)
X dead (should never be seen)
Z Defunct ("zombie") process, terminated but not reaped by its parent.
<< high-priority (not nice to other users)
N low-priority (nice to other users)
L has pages locked into memory (for real-time and custom IO)
s is a session leader
l is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)
+ is in the foreground process group

We can feel 'stuck' when a process goes into the "D" state usually, from time to time, Nvidia installer shows "D" state without any usefull logs when trying to install driver. We cannot kill "D" state processes, even with SIGKILL or kill -9. As the name implies, they are uninterruptible. You can only clear them by rebooting the server or waiting for the I/O to respond. Most reliable way is to look at the /proc, /proc/<pid>/ directory where it keeps information like:

1. cwd link to the current working directory
2. fd a dir with links to the open files (file descriptors)

Best Practices

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

References

• Linux Process

Related Pages

• Linux
• Server
• Hardware
• Network

Knowledge Graph

Related

→ Linux Kernel Tuning → systemd → LVM → iptables → Ubuntu → fstab → Linux Kernel