Does page-fault effect performance much, by forking child process?

I have a busy process which occupies 30% CPU and 1G memory usage, at Linux.
The process makes a snapshot every hour, by calling fork() to create a child process which writes all data to a file. It takes about 1second.

I found that the father process’s CPU usage becomes about 60% during the snapshot.

I guess the reason may be: forking a child makes most memory as Copy-on-write, and child process just reads memory so it does not trigger page-fault to copy pages, while the father process triggers many page-fault which results to a higher CPU usage.

Am I right? Can page-fault effects performance so much?

Thanks
Wu

== add stats ==

I count the page-fault by ps -o min_flt, and there are ~7k page-faults per second. Is it effects performance much?