Messages in this thread | | | Date | Wed, 9 Jan 2019 16:38:42 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH 6/6] perf thread-stack: Hide x86 retpolines |
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On Wed, Jan 09, 2019 at 11:18:35AM +0200, Adrian Hunter wrote: > x86 retpoline functions pollute the call graph by showing up everywhere > there is an indirect branch, but they do not really mean anything. Make > changes so that the default retpoline functions will no longer appear in > the call graph. Note this only affects the call graph, since all the > original branches are left unchanged. > > This does not handle function return thunks, nor is there any improvement > for the handling of inline thunks or extern thunks. > > Example: > > $ cat simple-retpoline.c > __attribute__((noinline)) int bar(void) > { > return -1; > } > > int foo(void) > { > return bar() + 1; > } > > __attribute__((indirect_branch("thunk"))) int main() > { > int (*volatile fn)(void) = foo; > > fn(); > return fn(); > } > $ gcc -ggdb3 -Wall -Wextra -O2 -o simple-retpoline simple-retpoline.c > $ objdump -d simple-retpoline > <SNIP> > 0000000000001040 <main>: > 1040: 48 83 ec 18 sub $0x18,%rsp > 1044: 48 8d 05 25 01 00 00 lea 0x125(%rip),%rax # 1170 <foo> > 104b: 48 89 44 24 08 mov %rax,0x8(%rsp) > 1050: 48 8b 44 24 08 mov 0x8(%rsp),%rax > 1055: e8 1f 01 00 00 callq 1179 <__x86_indirect_thunk_rax> > 105a: 48 8b 44 24 08 mov 0x8(%rsp),%rax > 105f: 48 83 c4 18 add $0x18,%rsp > 1063: e9 11 01 00 00 jmpq 1179 <__x86_indirect_thunk_rax> > <SNIP> > 0000000000001160 <bar>: > 1160: b8 ff ff ff ff mov $0xffffffff,%eax > 1165: c3 retq > <SNIP> > 0000000000001170 <foo>: > 1170: e8 eb ff ff ff callq 1160 <bar> > 1175: 83 c0 01 add $0x1,%eax > 1178: c3 retq > 0000000000001179 <__x86_indirect_thunk_rax>: > 1179: e8 07 00 00 00 callq 1185 <__x86_indirect_thunk_rax+0xc> > 117e: f3 90 pause > 1180: 0f ae e8 lfence > 1183: eb f9 jmp 117e <__x86_indirect_thunk_rax+0x5> > 1185: 48 89 04 24 mov %rax,(%rsp) > 1189: c3 retq > <SNIP> > $ perf record -o simple-retpoline.perf.data -e intel_pt/cyc/u ./simple-retpoline > [ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0,017 MB simple-retpoline.perf.data ] > $ perf script -i simple-retpoline.perf.data --itrace=be -s ~/libexec/perf-core/scripts/python/export-to-sqlite.py simple-retpoline.db branches calls > 2019-01-08 14:03:37.851655 Creating database... > 2019-01-08 14:03:37.863256 Writing records... > 2019-01-08 14:03:38.069750 Adding indexes > 2019-01-08 14:03:38.078799 Done > $ ~/libexec/perf-core/scripts/python/exported-sql-viewer.py simple-retpoline.db > > Before: > > main > -> __x86_indirect_thunk_rax > -> __x86_indirect_thunk_rax > -> foo > -> bar > > After: > > main > -> foo > -> bar >
hi, I still see them in kernel report.. after a while the output is shifted too far right out of the screen due to (I guess) this call/ret imbalance
[root@krava perf]# ./perf-with-kcore record pt -e intel_pt/cyc/k -a -- sleep 1 [root@krava perf]# ./perf-with-kcore script pt --call-trace -C 0 Xorg 2115 [000] 5850.032452321: cbr: 36 freq: 3621 MHz (171%) Xorg 2115 [000] 5850.032452351: ([kernel.kallsyms]) __list_add_valid Xorg 2115 [000] 5850.032452380: ([kernel.kallsyms]) perf_pmu_enable.part.101 Xorg 2115 [000] 5850.032452380: ([kernel.kallsyms]) __indirect_thunk_start Xorg 2115 [000] 5850.032452415: ([kernel.kallsyms]) __indirect_thunk_start Xorg 2115 [000] 5850.032452415: ([kernel.kallsyms]) __indirect_thunk_start Xorg 2115 [000] 5850.032452442: ([kernel.kallsyms]) __list_add_valid Xorg 2115 [000] 5850.032452457: ([kernel.kallsyms]) rb_next Xorg 2115 [000] 5850.032452494: ([kernel.kallsyms]) __x86_indirect_thunk_r12 Xorg 2115 [000] 5850.032452494: ([kernel.kallsyms]) __x86_indirect_thunk_r12 Xorg 2115 [000] 5850.032452535: ([kernel.kallsyms]) group_sched_in Xorg 2115 [000] 5850.032452535: ([kernel.kallsyms]) __indirect_thunk_start Xorg 2115 [000] 5850.032452535: ([kernel.kallsyms]) __indirect_thunk_start Xorg 2115 [000] 5850.032452548: ([kernel.kallsyms]) event_sched_in.isra.113 Xorg 2115 [000] 5850.032452548: ([kernel.kallsyms]) perf_event_set_state.part.70 Xorg 2115 [000] 5850.032452548: ([kernel.kallsyms]) perf_event_update_time Xorg 2115 [000] 5850.032452562: ([kernel.kallsyms]) perf_log_itrace_start Xorg 2115 [000] 5850.032452562: ([kernel.kallsyms]) __indirect_thunk_start Xorg 2115 [000] 5850.032452562: ([kernel.kallsyms]) __indirect_thunk_start Xorg 2115 [000] 5850.032452600: ([kernel.kallsyms]) perf_event_update_userpage Xorg 2115 [000] 5850.032452600: ([kernel.kallsyms]) calc_timer_values Xorg 2115 [000] 5850.032452600: ([kernel.kallsyms]) sched_clock_cpu Xorg 2115 [000] 5850.032452600: ([kernel.kallsyms]) sched_clock Xorg 2115 [000] 5850.032452600: ([kernel.kallsyms]) native_sched_clock Xorg 2115 [000] 5850.032452793: ([kernel.kallsyms]) __indirect_thunk_start Xorg 2115 [000] 5850.032452793: ([kernel.kallsyms]) __indirect_thunk_start Xorg 2115 [000] 5850.032452867: ([kernel.kallsyms]) arch_perf_update_userpage Xorg 2115 [000] 5850.032452867: ([kernel.kallsyms]) using_native_sched_clock Xorg 2115 [000] 5850.032452867: ([kernel.kallsyms]) sched_clock_stable Xorg 2115 [000] 5850.032452867: ([kernel.kallsyms]) cyc2ns_read_begin Xorg 2115 [000] 5850.032453157: ([kernel.kallsyms]) cyc2ns_read_end Xorg 2115 [000] 5850.032453194: ([kernel.kallsyms]) __indirect_thunk_start Xorg 2115 [000] 5850.032453194: ([kernel.kallsyms]) __indirect_thunk_start Xorg 2115 [000] 5850.032453206: ([kernel.kallsyms]) __list_add_valid
jirka
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