Thanks, Anoop! But I don't think you understood the point I was trying to get across. I was definitely not trying to compare nginx and apache memory usage. Let's just ignore that part was ever said. :)

I'm trying to understand why Nginx is using 2x the memory usage when the HUP signal is sent, i.e. the normal reload process.

When you use the USR2/QUIT method, i.e. the binary upgrade process, it doesn't do this.

It's a big problem on high vhost servers when you go from normally using 1G of ram to using 2G and then 4G during subsequent reloads.

It's that brief 4G spike that initially caught my attention. But then I noticed that it was always using 2x more ram. Whoa!

This is super easy to reproduce so I invite you to test it yourself.