tsippi wrote:
Like many other people, ever since I "upgraded" to Catalina 24 hours ago, NSurlsessiond is using up an enormous amount of CPU power and is burning through my battery. A quick web search indicates this is a very common problem. Why is Apple not responding? What can people do to fix this? (Early 2015 13 inch Retina Macbook Pro, 3.1 GHz; 16 GB 1867 MHz.)
https://discussions.apple.com/thread/7525492
To trouble shoot further you can:
—Try a SafeBoot https://support.apple.com/en-us/HT201262
Takes noticeable longer to get to the login screen, does a 5-15 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache, etc. Login and test. Reboot and test as caches get rebuilt.
In Safe mode third party system modifications and system accelerations are disabled, it removes malware, etc hampering smooth operation, however a reboot will put it back to normal mode.
This test will tell you if third party interference; extensions etc are not loaded in safe boot mode.
—Test issue in another user (or guest user) account https://support.apple.com/en-us/HT204443
This will tell you if it a universal issue or isolated to your user/admin account.