Os Memory Mlock

In this tutorial, you'll learn about How to Fix Memory Locking Errors. We cover key concepts, practical examples, and best practices.

Fix memory locking errors when critical data paged out to swap causing latency spikes.

Quick Fix

Wrong

import os, mmap
secret=bytes(1024)
# secret may be paged out at any time!

Sensitive data (passwords, keys) may be written to swap. Exposed and slow.

Right

import mmap, os
# Lock memory to prevent swapping:
pid=os.getpid()
try:
    import ctypes
    libc=ctypes.CDLL('libc.so.6')
    libc.mlock(ctypes.c_void_p(id(secret)), 4096)
    # or use mlockall:
    libc.mlockall(2)  # MCL_CURRENT
    print('Memory locked')
except: print('mlock not available (need root/CAP_IPC_LOCK)')

mlock prevents pages from being swapped. Critical for security and latency-sensitive code.

Prevention

Use mlock() for sensitive data and real-time critical buffers. Requires CAP_IPC_LOCK.

DodaTech Tools

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