Are you talking 'C' here?
If so, which compiler?

You need to read the appropriate manual for your compiler!

"so for this function some RAM area gets allocated"

In Keil C51, parameters & local variables go on the "virtual stack" for reentrant functions.

"i carry out few PUSH operations"

'C' does not have a 'PUSH'
The 8051 PUSH instruction always and only affects the hardware stack

It's because the 8051 hardware stack is so small the (some) 8051 'C' implementations introduce this "virtual stack" stuff - the hardware stack would soon overflow if it were used for reentrant functions!