Pu usage is very high

Why cpu usage is very high after using cf, the ddos mode is very low, and I have not encountered any attacks.

Switching to Cloudflare generally doesn’t do that, you should check with your host or use tools like htop (linux command line) to see what’s using your CPU.

I use other providers without this problem, I think it is not the configuration problem, so that cf has been reading the server’s files during the caching process.

In the attack mode, there is no such high CPU usage.