CODEWITHSUNDEEP
kcachegrind
A. M. Anisul Huq
A. M. Anisul Huq

Reputation: 1

Confusing output from Kcachegrind

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Hi, I am profiling my C code with Kcachegrind. But I am confused with the output tree-map view of the call graph (see the above mentioned link). I have compiled the code: valgrind --tool=callgraph ./Program_name and then kcachegrind callgrind.out.8389. I have the following questions:

  1. Above the main() function, u will see a "below main()" and 0x08048bb0 functions. What r these? Is it because the compiler/OS doesn't load the program image and jumps to main() directly. I have read that, before calling main(), a process executes a bulk of code to “clean up the room for execution”. Is this the reason?

  2. In the lower part of the tree, u will also see a lot of functions with hexadecimal numbers instead of names. Why is this?

  3. Are these hexadecimal numbers absolute addresses (i.e. not offset) or virtual addresses (or Symbol) of the code section of these functions? or not?

  4. I have compiled my program in Ubuntu 10.10 using the -g option. Do these hexadecimal numbers have something to do with the absence of "debugging information"?

  5. I have tried to use "nm program_name" to figure out whats happening? For the above attached call graph, I have the following output:

root@xTR:/home/ahuq/system/client/xTR# nm UDPClientProject 
0804af14 d _DYNAMIC
0804aff4 d _GLOBAL_OFFSET_TABLE_
08049b4c R _IO_stdin_used
         w _Jv_RegisterClasses
0804af04 d __CTOR_END__
0804af00 d __CTOR_LIST__
0804af0c D __DTOR_END__
0804af08 d __DTOR_LIST__
08049ebc r __FRAME_END__
0804af10 d __JCR_END__
0804af10 d __JCR_LIST__
0804b0a0 A __bss_start
         U __cxa_atexit@@GLIBC_2.1.3
0804b098 D __data_start
08049b00 t __do_global_ctors_aux
08048c30 t __do_global_dtors_aux
0804b09c d __dso_handle
08048be0 T __gmon_start__
08049aba T __i686.get_pc_thunk.bx
0804af00 d __init_array_end
0804af00 d __init_array_start
08049a50 T __libc_csu_fini
08049a60 T __libc_csu_init
         U __libc_start_main@@GLIBC_2.0
         U __monstartup@@GLIBC_2.0
         U __stack_chk_fail@@GLIBC_2.4
0804b0a0 A _edata
0804b0c4 A _end
08049b2c T _fini
08049b48 R _fp_hw
0804890c T _init
         U _mcleanup@@GLIBC_2.0
08048bb0 T _start
080490aa T access_file_insert_data
         U alarm@@GLIBC_2.0
0804922d T append
08049ac0 T atexit
         U bzero@@GLIBC_2.0
0804b0a4 b called.3477
         U calloc@@GLIBC_2.0
         U ceil@@GLIBC_2.0
08049517 T client_timeout_signal_handle
0804b0a8 b completed.7065
0804b098 W data_start
080496e5 T delete_query
080494cc T display
0804b0ac b dtor_idx.7067
0804b0b4 B err
08049658 T err_message
08049b48 A etext
         U exit@@GLIBC_2.0
         U fclose@@GLIBC_2.1
         U fgets@@GLIBC_2.0
         U fopen@@GLIBC_2.1
         U fprintf@@GLIBC_2.0
08048c90 t frame_dummy
0804953a T get_map_notify_packet
         U htons@@GLIBC_2.0
         U inet_pton@@GLIBC_2.0
08049733 T insert_query
08048cb4 T main
         U malloc@@GLIBC_2.0
080495c6 T map_notify_packet_initialization
08048f3c T map_register_packet_initialization
         U mcount@@GLIBC_2.0
         U memcpy@@GLIBC_2.0
         U memset@@GLIBC_2.0
         U mysql_close@@libmysqlclient_16
         U mysql_errno@@libmysqlclient_16
         U mysql_error@@libmysqlclient_16
         U mysql_init@@libmysqlclient_16
         U mysql_query@@libmysqlclient_16
         U mysql_real_connect@@libmysqlclient_16
         U mysql_sqlstate@@libmysqlclient_16
0804b0c0 B num_of_mapping
         U perror@@GLIBC_2.0
0804b0b0 B position
         U printf@@GLIBC_2.0
         U puts@@GLIBC_2.0
         U recvfrom@@GLIBC_2.0
         U sendto@@GLIBC_2.0
         U signal@@GLIBC_2.0
         U socket@@GLIBC_2.0
0804b0a0 B stderr@@GLIBC_2.0
         U strcat@@GLIBC_2.0
         U strcpy@@GLIBC_2.0
         U strlen@@GLIBC_2.0
         U strtok@@GLIBC_2.0
08049781 T tcp_server_access_main
0804b0b8 B udp_cli_program_cycle
0804b0bc B xx1
  1. I am not seeing the Hexadecimal addresses from the call graph present in the "nm" ouput. I am confused.

Please help me.

Bye.

Upvotes: 0

Views: 937

Answers (1)

David Schwartz
David Schwartz

Reputation: 182733

Nodes above main correspond to the code that calls main and returns from it. This is the code that initializes globals and cleans up.

The functions with hexadecimal numbers instead of names correspond to places where debug information or stack information was not available. If you notice, they're typically inside or between libraries. The addresses are absolute, virtual addresses. You won't find them in your program because either they're in dynamically-loaded libraries with no debug information, they were relocated, or they're in parts of your program that weren't compiled with debug symbols (such as code from static libraries). If they were that easy to find, they would have been found for you automatically.

In any event, they only account for about 12% of the consumption, total. They're between the SQL code and the XML code.

Upvotes: 1

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