Spotlight

Forever33 wrote:

It seems spotlight in Big Sur uses much CPU. How to turn off Spotlight ?

I would not recommend turning it off.

Spot light is the search index use by the macOS for machine search, Finder Directory search, Mail Search, etc....

If you have an issue simply rebuild the index to sort issues—

Rebuild the Spotlight index on your Mac - Apple Support

If you still have an issue try a SafeBoot to clear system caches among others, reboot as normal as cache files get rebuild automatically.

When you first power up your Mac, Spotlight will spawn several mdworker processes to index what was not previously indexed on your startup drive. Additionally, I just observed Spotlight using 4 cores of my M1 mini at 100% for its 15 spawned mdworker processes following a Time Machine backup. In either case, this is perfectly normal and indexing does not run for an extended period.