Hi, I was running some perf mem test for an upcoming patch when I realize that precise=2 was broken on 3.18. It seems it never (or extremely rarely) correct the off-by-one error, when until 3.18-rc4 it was 100% on the same program. So something was introduced that broke the asm walker in perf_event_intel_ds.c.
Looking at the log of that file, I can see one change that could have some impact: Author: Dave Hansen <dave.han...@linux.intel.com> 6ba48ff x86: Remove arbitrary instruction size limit in instruction decoder if I use a kernel without this fix (prior to that commit), then correction works. Any kernel after fails. I have not investigated why but may you have an idea. To reproduce try using perf mem -t load rec my_load_test, then use perf report to navigate to the assembly view, the samples should be on load instructions, not on the instructions following them. If you use perf mem -t load rec -vv you can verify that precise=2. So something is not working anymore in the instruction decoder that the fixup routine bails out. Any clue? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/