Messages in this thread | | | Date | Fri, 15 Nov 2013 06:46:09 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] perf top: Make -g refer to callchains |
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btw., here's some 'perf top' call graph performance and profiling quality feedback, with the latest perf code:
'perf top --call-graph fp' now works very well, using just 0.2% of CPU time on a fast system:
4676 mingo 20 0 612m 56m 9948 S 1 0.2 0:00.68 perf
'perf top --call-graph dwarf' on the other hand is horrendously slow, using 20% of CPU time on a 4 GHz CPU:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 4646 mingo 20 0 658m 81m 12m R 19 0.3 0:18.17 perf
On another system with a 2.4GHz CPU it's taking up 100% of CPU time (!):
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 8018 mingo 20 0 290320 45220 8520 R 99.5 0.3 0:58.81 perf
Profiling 'perf top' shows all sorts of very high dwarf processing overhead:
# # Overhead Command Shared Object Symbol # ........ ....... ......................... ................................................. # 7.08% perf perf [.] access_mem 7.03% perf perf [.] dso__data_read_offset 5.83% perf perf [.] maps__find 5.64% perf libunwind-x86_64.so.8.0.1 [.] 0x000000000000ba25 4.75% perf perf [.] thread__find_addr_map 3.81% perf [kernel.kallsyms] [k] unmap_single_vma 2.57% perf perf [.] map__map_ip 2.48% perf libelf-0.156.so [.] 0x0000000000003a84 2.12% perf [kernel.kallsyms] [k] memset 2.12% perf perf [.] dso__data_read_addr 2.10% perf libc-2.17.so [.] __memcpy_sse2 1.72% perf libc-2.17.so [.] __memset_sse2 1.58% perf [kernel.kallsyms] [k] page_fault 1.56% perf libc-2.17.so [.] __memset_x86_64 1.44% perf perf [.] find_proc_info 1.25% perf libelf-0.156.so [.] elf_end 1.19% perf [kernel.kallsyms] [k] flush_tlb_mm_range 1.06% perf libc-2.17.so [.] vfprintf 1.04% perf libunwind-x86_64.so.8.0.1 [.] _Ux86_64_dwarf_search_unwind_table 1.00% perf [kernel.kallsyms] [k] __audit_syscall_exit 0.94% perf libc-2.17.so [.] _int_free 0.92% perf libc-2.17.so [.] _int_malloc 0.84% perf libc-2.17.so [.] __memcmp_sse2 0.81% perf [kernel.kallsyms] [k] unmapped_area_topdown 0.71% perf [kernel.kallsyms] [k] system_call 0.71% perf [kernel.kallsyms] [k] system_call_after_swapgs 0.65% perf [kernel.kallsyms] [k] sysret_check 0.63% perf perf [.] dso__find_symbol 0.58% perf [kernel.kallsyms] [k] clear_page_c 0.58% perf [kernel.kallsyms] [k] handle_mm_fault 0.56% perf libc-2.17.so [.] __sigprocmask 0.55% perf [kernel.kallsyms] [k] copy_user_generic_string 0.51% perf [kernel.kallsyms] [k] __do_fault 0.49% perf [kernel.kallsyms] [k] find_vma 0.47% perf libpthread-2.17.so [.] __libc_close 0.44% perf [kernel.kallsyms] [k] __audit_syscall_entry 0.44% perf [kernel.kallsyms] [k] mmap_region 0.42% perf [kernel.kallsyms] [k] _raw_spin_lock 0.41% perf [kernel.kallsyms] [k] kmem_cache_free 0.40% perf [kernel.kallsyms] [k] kmem_cache_alloc 0.40% perf libpthread-2.17.so [.] pthread_mutex_unlock 0.37% perf [kernel.kallsyms] [k] perf_event_aux_ctx 0.37% perf [kernel.kallsyms] [k] do_munmap 0.37% perf libc-2.17.so [.] free [...]
Thanks,
Ingo
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