[lttng-dev] lttng function tracing nginx problem

[Alexandre Montplaisir]

Hi,

Is it possible that nginx forks other processes, and the main process 
stays there doing almost nothing? In such a case, you would need to also 
preload "liblttng-ust-fork.so", so that UST can follow through fork() 
calls. See the section USING LTTNG UST WITH DAEMONS of "man lttng-ust".

Cheers,
Alexandre


On 2015-05-20 09:02 PM, gang li wrote:
>
> [quehan at localhost objs]$ file ./nginx
> ./nginx: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, BuildID[sha1]=0xb7659abd6bd962b7033f3cc495ac8bb44ac9f044, not stripped
>
>
>
> CFLAGS = -finstrument-functions -pipe -W -Wall -Wpointer-arith -Wno-unused-parameter -Werror -g
> [quehan at localhost objs]$ nm ./nginx | grep __cyg_profile_func                 U __cyg_profile_func_enter@@GLIBC_2.2.5
>
>
>                   U __cyg_profile_func_exit@@GLIBC_2.2.5
> [quehan at localhost objs]$ cat /proc/2046/maps | grep lttng7f2298000000-7f2298009000 r-xp 00000000 fd:01 103870944                  /usr/lib/liblttng-ust-tracepoint.so.0.0.07f2298009000-7f2298208000 ---p 00009000 fd:01 103870944                  /usr/lib/liblttng-ust-tracepoint.so.0.0.07f2298208000-7f2298209000 r--p 00008000 fd:01 103870944                  /usr/lib/liblttng-ust-tracepoint.so.0.0.07f2298209000-7f229820a000 rw-p 00009000 fd:01 103870944                  /usr/lib/liblttng-ust-tracepoint.so.0.0.07f2298aaa000-7f2298af2000 r-xp 00000000 fd:01 103870951                  /usr/lib/liblttng-ust.so.0.0.07f2298af2000-7f2298cf2000 ---p 00048000 fd:01 103870951                  /usr/lib/liblttng-ust.so.0.0.07f2298cf2000-7f2298cf4000 r--p 00048000 fd:01 103870951                  /usr/lib/liblttng-ust.so.0.0.07f2298cf4000-7f2298cf9000 rw-p 0004a000 fd:01 103870951                  /usr/lib/liblttng-ust.so.0.0.07f2299d6a000-7f2299d6c000 r-xp 00000000 fd:01 103870981                  /usr/lib/liblttng-ust-cyg-profile-fast.so.0.0.07f2299d6c000-7f2299f6c000 ---p 00002000 fd:01 103870981                  /usr/lib/liblttng-ust-cyg-profile-fast.so.0.0.07f2299f6c000-7f2299f6d000 r--p 00002000 fd:01 103870981                  /usr/lib/liblttng-ust-cyg-profile-fast.so.0.0.07f2299f6d000-7f2299f6e000 rw-p 00003000 fd:01 103870981                  /usr/lib/liblttng-ust-cyg-profile-fast.so.0.0.07f229a18a000-7f229a18b000 r--s 00000000 00:11 18728                      /dev/shm/lttng-ust-wait-5-1000
>
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> 7f229a18b000-7f229a18c000 r--s 00000000 00:11 18727                      /dev/shm/lttng-ust-wait-5
>
> Nginx is a very famous lightweight http server, and I use the latest lttng suits, I can't resolve this.
>
> Date: Wed, 20 May 2015 16:28:41 +0000
> From: mathieu.desnoyers at efficios.com
> To: portlet at outlook.com
> CC: lttng-dev at lists.lttng.org
> Subject: Re: [lttng-dev] lttng function tracing nginx problem
>
>
> hi all,
> I compile the nginx-1.4.7 with FLAG -finstrument-functions , and start nginx like this:
> LD_PRELOAD=liblttng-ust-cyg-profile-fast.so  ./nginx
> Then I use the command lttng list --userspace and got nothing like this:
> UST events:-------------None
> I don't understand why I can't get the func_exit/entry events from nginx.
> Is the "ngix" executable a binary executable or a shell script ?
>
> Can you give us the output of "file ./ngix" ?
>
> You might want to try
>
> export LD_PRELOAD=liblttng-ust-cyg-profile-fast.so
> ./ngix
>
> Thanks,
>
> Mathieu
>
>
>
> By the way, I test function tracing with a single c source file and works well, output like this:
> UST events:-------------
> PID: 4687 - Name: ./tt      lttng_ust_cyg_profile:func_exit (loglevel: TRACE_DEBUG_FUNCTION (12)) (type: tracepoint)      lttng_ust_cyg_profile:func_entry (loglevel: TRACE_DEBUG_FUNCTION (12)) (type: tracepoint)      lttng_ust_tracef:event (loglevel: TRACE_DEBUG (14)) (type: tracepoint)
>
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>        ust_baddr_statedump:soinfo (loglevel: TRACE_DEBUG_LINE (13)) (type: tracepoint)
>
> Wishing for help.