Today, I have noticed that, an application named kworker/u:4 using phone's battery. I haven't seen this app before on battery usage section. Also, I have noticed kswapd0 application using battery, last week. Are they normal operations?
I am using unrooted Xiaomi phone.
Yes, this is completely normal (although on Android you would expect it to be combined with the "System" usage). See Kworker, what is it and why is it hogging so much CPU?
"kworker" is a placeholder process for kernel worker threads, which perform most of the actual processing for the kernel, especially in cases where there are interrupts, timers, I/O, etc. These typically correspond to the vast majority of any allocated "system" time to running processes.
Similarly, kswapd is responsible for managing some kernel memory swapping; you may have seen this because your were running low on memory at some point.
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