[AGENT++] Memory management of AGENT++

[Apostolos Manolitzas]

On 07/27/2010 11:55 AM, wancheng82 wrote:
> I use AGENT++ in one open source project (www.pica8.org), and it is very convenient.
> I test very large MAC address table in BRIDGE-MIB. 
> At first it seems AGENT++ has memory leak int test 1.1) and 1.2), but when I do more test in 1.3) and 1.4), it suprises me.
>
> Test 1)
> 1.1)Add 30000 MAC address to BRIDGE-MIB.
>      The code :
>     //MAC is in char buf[]
>     if((row = dot1dTpFdbEntry::instance->find_index(buf)) == NULL)
>        row = dot1dTpFdbEntry::instance->add_row(buf);
>    The memory test:
>     USER       PID  %CPU  %MEM    VSZ   RSS   TTY      STAT START   TIME COMMAND
>     root     23482  11.2     2.2      72772 68976 pts/10   S+   16:43      0:02 ./agent   =====>about 72MB
>
> 1.2)Rrmove 30000 MAC address from BRIDGE-MIB
>      The code:
>      //MAC is in char buf[]
>      if((row = dot1dTpFdbEntry::instance->find_index(buf)) != NULL)
>         dot1dTpFdbEntry::instance->remove_row(buf);
>     The memory test:
>     USER       PID  %CPU  %MEM    VSZ   RSS   TTY      STAT START   TIME COMMAND
>      root     23482  2.6        2.2  72772   68976 pts/10   S+    16:43    0:04 ./agent       ======>still about 72MB
>
> 1.3)Add another 30000 MAC address to BRIDGE-MIB(different from 1.1).
>      The code :
>     //MAC is in char buf[]
>     if((row = dot1dTpFdbEntry::instance->find_index(buf)) == NULL)
>        row = dot1dTpFdbEntry::instance->add_row(buf);
>    The memory test:
>     USER       PID  %CPU  %MEM    VSZ   RSS   TTY      STAT START   TIME COMMAND
>     root       23482  1.6       2.2  72772 68984 pts/10       S+   16:43   0:06 ./agent   ======>72MB
>
> 1.4)Rrmove 30000 MAC address from BRIDGE-MIB
>      The code:
>      //MAC is in char buf[]
>      if((row = dot1dTpFdbEntry::instance->find_index(buf)) != NULL)
>         dot1dTpFdbEntry::instance->remove_row(buf);
>     The memory test:
>     USER       PID  %CPU  %MEM    VSZ   RSS   TTY      STAT START   TIME COMMAND
>       root     23482  1.6        2.2  72772 68984 pts/10   S+      16:43   0:08 ./agent   ======>72MB
>
> Question:
> It seems that AGENT++ has its own memory management mechanism, is that right? 
> How should I know them from the code?  I did not find them in code, because remove_row will delete the row. 
>
> Thank you.
> Robin
>   

    Try to use struct mallinco [1] for actually metering the memory
allocated and freed because Linux malloc implementation of stdlibc does
some kind of caching in order to reuse the data.
Especially check the |fordblks part.

|cheers,
-Apostolos

[1]
http://www.gnu.org/s/libc/manual/html_node/Statistics-of-Malloc.html#Statistics-of-Malloc