[mort96]

"Page" is OS terminology. "Arena" is Go terminology. An arena is made up of sequential pages. Go asks the OS for 64MB of sequential memory, and calls that 64MB chunk an arena; this is consistent with the text you quoted. It is not incorrect.

[burntcaramel]

Thank you, I stand corrected! I must have been tired originally reading this.

[lucketone]

Cunningham’s Law in action (thanks for the summary)