Hello Sanghee,
the PFC is part of normal working conditions, if PFC fails it is likely the device will have a lot problems
Presence of DFCs is optional and needed only to move to distributed CEF.
the SW performance can be much less then that of HW assisted forwarding.
Just to make an example a C7200 VXR with NPE-G2 is declared able to perform 2,000,000 pps
Cisco 7206VXR (NPE-G2) processor (revision A) with 917504K/65536K bytes of memory.
Processor board ID 35211565
MPC7448 CPU at 1666Mhz, Implementation 0, Rev 2.1
6 slot VXR midplane, Version 2.11
main cpu of RP or SP in a C6500 with sup 720 3B
cisco WS-C6506-E (R7000) processor (revision 1.1) with 458720K/65536K bytes of memory.
Processor board ID SAL10425HVV
SR71000 CPU at 600Mhz, Implementation 0x504, Rev 1.2, 512KB L2 Cache
Last reset from s/w reset
So you can think of 1 Mpps roughly. but again this should never happen in real world
To be noted that Control plane policing CoPP and the special rate limits allow to protect main cpu
see
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/dos.html#wp1141467
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SXF/native/configuration/guide/dos.html#wp1141802
Hope to help
Giuseppe