Measuring L2 -> L1 Fill latency..

I am trying to measure the L2 -> L1 Fill latency. I'm using PMC 0x48 umask=0x01. This increments each cycle the number of Line Fill Buffers currently allocated, right? If I also tabulate the number of allocations in the L1D (PMC 51 umask=0x01): <# cycles a fill takes from L2 -> L1> =(# active LFB per instruction) / (# L1D allocations made per instruction) Is this correct? perfwise