Messages in this thread | | | Date | Mon, 15 Dec 2008 16:07:13 -0500 (EST) | From | Vince Weaver <> | Subject | Re: [patch] Performance Counters for Linux, v4 |
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Hello
I'm trying a more complicated benchmark and getting even stranger results.
This is still on the Q6600 machine
The benchmark does a loop, reading some memory. It should have roughly: 12295 instructions 4096 memory loads 4096 branches
perfmon3 is close on all of these stats, and this is consistent across runs with a small variation (+/- 3 or so).
The timec program returns 0 (!) for all of the stats except retired instruction count! And with certain combinations of counters I get 0 for all counts. No error messages are printed.
Is this expected behavior?
The test program can be had from: http://www.csl.cornell.edu/~vince/projects/perf_counter/
Details below:
# # Perfmon results #
# First, trying to read all 5 events at once fails, only 4 counters # avail
tasse:~/assembly_tests% pfmon -e INSTRUCTIONS_RETIRED,BRANCH_INSTRUCTIONS_RETIRED,L1D_ALL_CACHE_REF,MEM_LOAD_RETIRED:L1D_MISS ./read_test cannot configure events: set0 events incompatible or too many events
# Cache results are close to expected, L1D looks a little high
tasse:~/assembly_tests% pfmon -e INSTRUCTIONS_RETIRED,L1D_ALL_CACHE_REF,MEM_LOAD_RETIRED:L1D_MISS ./read_test 12299 INSTRUCTIONS_RETIRED 4164 L1D_ALL_CACHE_REF 4 MEM_LOAD_RETIRED:L1D_MISS
# Branch results. Close to what they should be, though a bit higher # than expected.
tasse:~/assembly_tests% pfmon -e INSTRUCTIONS_RETIRED,BRANCH_INSTRUCTIONS_RETIRED,MISPREDICTED_BRANCH_RETIRED ./read_test 12299 INSTRUCTIONS_RETIRED 4102 BRANCH_INSTRUCTIONS_RETIRED 1 MISPREDICTED_BRANCH_RETIRED
# # performance counter v4 #
# Including all stats gives no errors, but gives no results # either
tasse:~/assembly_tests% ./timec -e 0 -e 1 -e 2 -e 3 -e 4 -e 5 ./read_test
Performance counter stats for './read_test':
0.716 task clock ticks (millisecs)
85049 cycles (events) 0 instructions (events) 0 cache references (events) 0 cache misses (events) 0 branches (events) 0 branch misses (events)
# # If I include the cycles count, I consistently get 0 # for all counts???
tasse:~/assembly_tests% ./timec -e 0 -e 1 -e 2 -e 3 ./read_test
Performance counter stats for './read_test':
0.520 task clock ticks (millisecs)
73833 cycles (events) 0 instructions (events) 0 cache references (events) 0 cache misses (events)
# # If I drop the cycles count, I get an instruction count # with a value 2300 too high (see previous e-mail) # And really low cache values.
tasse:~/assembly_tests% ./timec -e 1 -e 2 -e 3 ./read_test
Performance counter stats for './read_test':
0.723 task clock ticks (millisecs)
14644 instructions (events) 8 cache references (events) 0 cache misses (events)
# # And the branch stats don't work either #
tasse:~/assembly_tests% ./timec -e 1 -e 4 -e 5 ./read_test
Performance counter stats for './read_test':
0.711 task clock ticks (millisecs)
14643 instructions (events) 0 branches (events) 0 branch misses (events)
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