Process is getting slow while tcpdump is runing

when I start tcpdump all process for file transfer is slowing down and when I stop tcpdump file transfer is processes running normal.
what was the reason for that?
command : sudo tcpdump port not 8080 -w path_of_file.pcap

try tcpdump with output in different directory than workspace/
also you can limit tcpdump to a specfic port which will significanlty decrease it size