Confusion about lts srcunit tex

Hi, I’m testing some metrics mentioned at GTC Video.

Metrics at L2 cache includes srcunit_tex. I wrote a simple kernel (only has global memory) to test metric lts__t_requests_srcunit_tex_op_read (# of LTS requests from unit TEX for reads). And I can actually reproduce some output (not zero).
Then I choose metric lts__t_requests_srcunit_l1_op_read (# of LTS requests from unit L1 for reads), but I got a value of zero.

Now I have a question about their name. Why the output of metrics in constrast to their name?
Or did I misunderstand something?
And how can i test metric lts__t_requests_srcunit_l1_op_read with a value of non-zero?