inotify.max_user_watches Memory Usage

Per-Watch Cost:

• 32-bit systems: ~540 bytes per watch
• 64-bit systems: ~1 KB per watch

Example: With max_user_watches = 1048576:

• Worst case (all watches used): ~1 GB of kernel memory on 64-bit systems
• Real-world usage: Typically much less, as not all watches are actively used

⚠️ Important: Inotify uses kernel memory which cannot be swapped out. But it only uses memory when the watches are used not when you set the limit.

Memory is used when you use the watches

# Setting this limit doesn't use any memory yet
# 
# Memory is only used when watches are actually created
# If you only have 1000 active watches, you're using ~1MB, not 1GB
fs.inotify.max_user_watches = 1048576