US>What is the unit of memory swap-out swap-in for Linux?

How does Linux swap out and swap in memory?

• Is it per page (approximately 4kb)?
• Or is it a little larger, internal structural unit around memory management?

This is because I think heap fragmentation occurs when dealing with scripting languages.Even if it's fragmentation, I thought it wouldn't be such a problem if the swap worked well.(If sufficient swapping is required) In that case, I'm asking because I think it's relatively important how many units the operating system is determining which area to swap.