3 ms·

I profiled my program looking for TLB misses, and got 0 dTLB misses (https://gist.github.com/jvns/a42ff6f48c659cfc4600 https://gist.github.com/jvns/a42ff6f48c65

by jvns 12y ago

I profiled my program looking for TLB misses, and got 0 dTLB misses (https://gist.github.com/jvns/a42ff6f48c659cfc4600 https://gist.github.com/jvns/a42ff6f48c659cfc4600).

nkurz 12y ago
I think 'perf' is probably lying to you. Although maybe it's not a lie, as your Gist does contain that line '<not supported> dTLB-misses'. Perf tries very hard to be non-CPU specific, and thus doesn't do a great job of handling the CPU specific stuff. What processor are you running this on? If Intel, you might have luck with some of the more Intel specific wrappers here: https://github.com/andikleen/pmu-tools https://github.com/andikleen/pmu-tools You also might have better luck with 'likwid': https://code.google.com/p/likwid/ https://code.google.com/p/likwid/ Here's the arguments I was giving it to check: sudo likwid -C 1 -g \ INSTR_RETIRED_ANY:FIXC0, \ CPU_CLK_UNHALTED_CORE:FIXC1,\ CPU_CLK_UNHALTED_REF:FIXC2, \ DTLB_LOAD_MISSES_WALK_COMPLETED:PMC0 \ ./bytesum 1gb_file | INSTR_RETIRED_ANY | 7.38826e+08 | | CPU_CLK_UNHALTED_CORE | 5.42765e+08 | | CPU_CLK_UNHALTED_REF | 5.42753e+08 | | DTLB_LOAD_MISSES_WALK_COMPLETED | 1.04509e+06 | sudo likwid -C 1 -g \ INSTR_RETIRED_ANY:FIXC0, \ CPU_CLK_UNHALTED_CORE:FIXC1,\ CPU_CLK_UNHALTED_REF:FIXC2, \ DTLB_LOAD_MISSES_WALK_COMPLETED:PMC0 \ ./hugepage_prefetch 1gb_file | INSTR_RETIRED_ANY | 5.79098e+08 | | CPU_CLK_UNHALTED_CORE | 2.63809e+08 | | CPU_CLK_UNHALTED_REF | 2.63809e+08 | | DTLB_LOAD_MISSES_WALK_COMPLETED | 11970 | The other main advantage of 'likwid' is that it allows you to profile just a section of the code, rather than the program as a whole. For odd political reasons, 'perf' doesn't make this possible. ps. I think your 'argc' check is off by one. Since the name of the program is in argv[0], and argc is the length of argv, you want to check 'argc != 2' to confirm that a filename has been given.

by jvns 12y ago

I profiled my program looking for TLB misses, and got 0 dTLB misses (https://gist.github.com/jvns/a42ff6f48c659cfc4600 https://gist.github.com/jvns/a42ff6f48c659cfc4600).

nkurz 12y ago

I think 'perf' is probably lying to you. Although maybe it's not a lie, as your Gist does contain that line '<not supported> dTLB-misses'. Perf tries very hard to be non-CPU specific, and thus doesn't do a great job of handling the CPU specific stuff. What processor are you running this on? If Intel, you might have luck with some of the more Intel specific wrappers here: https://github.com/andikleen/pmu-tools https://github.com/andikleen/pmu-tools You also might have better luck with 'likwid': https://code.google.com/p/likwid/ https://code.google.com/p/likwid/ Here's the arguments I was giving it to check: sudo likwid -C 1 -g \ INSTR_RETIRED_ANY:FIXC0, \ CPU_CLK_UNHALTED_CORE:FIXC1,\ CPU_CLK_UNHALTED_REF:FIXC2, \ DTLB_LOAD_MISSES_WALK_COMPLETED:PMC0 \ ./bytesum 1gb_file | INSTR_RETIRED_ANY | 7.38826e+08 | | CPU_CLK_UNHALTED_CORE | 5.42765e+08 | | CPU_CLK_UNHALTED_REF | 5.42753e+08 | | DTLB_LOAD_MISSES_WALK_COMPLETED | 1.04509e+06 | sudo likwid -C 1 -g \ INSTR_RETIRED_ANY:FIXC0, \ CPU_CLK_UNHALTED_CORE:FIXC1,\ CPU_CLK_UNHALTED_REF:FIXC2, \ DTLB_LOAD_MISSES_WALK_COMPLETED:PMC0 \ ./hugepage_prefetch 1gb_file | INSTR_RETIRED_ANY | 5.79098e+08 | | CPU_CLK_UNHALTED_CORE | 2.63809e+08 | | CPU_CLK_UNHALTED_REF | 2.63809e+08 | | DTLB_LOAD_MISSES_WALK_COMPLETED | 11970 | The other main advantage of 'likwid' is that it allows you to profile just a section of the code, rather than the program as a whole. For odd political reasons, 'perf' doesn't make this possible. ps. I think your 'argc' check is off by one. Since the name of the program is in argv[0], and argc is the length of argv, you want to check 'argc != 2' to confirm that a filename has been given.