[lttng-dev] (no subject)
Mehran Khan
i at mehrankhan.com
Wed Jan 22 15:01:09 EST 2014
Hello Simon,
it did solve my problem. Cannot thank you enough!
I will share my work once I get to any interesting point.
Thank you again,
Mehran
On Wed, Jan 22, 2014 at 8:39 AM, Simon Marchi <simon.marchi at polymtl.ca>wrote:
> Hi Mehran,
>
> I'll try to correct you where I can.
>
> On 21 January 2014 18:34, Mehran Khan <i at mehrankhan.com> wrote:
> > Hello everyone,
> > I have been trying to instrument the Apache web server, the latest
> version
> > (2.4.7 from the URL http://httpd.apache.org/download.cgi#apache24) for
> LTTng
> > UST tracing
> > 1. To start with the simplest case, I created a *.tp file named
> > smallestTracePoint.tp with the content below
> > TRACEPOINT_EVENT(
> > mk,
> > apache_process_entry,
> > TP_ARGS(),
> > TP_FIELDS()
> > )
>
> This is good.
>
> > 2. Then I ran the following
> > lttng-gen-tp smallestTracePoint.tp -o smallestTracePoint.h -o
> > smallestTracePoint.c
> >
> > which generated the files smallestTracePoint.c and smallestTracePoint.h
>
> You can just say
> $ lttng-gen-tp smallestTracePoint.tp
> and it will generate the .h and .c.
>
> > 3. Then, I put the smallestTracePoint.h and smallestTracePoint.c in
> > httpd-2.4.7/server directory,
> > included smallestTracePoint.h in the main.c file and added trace
> points in
> > the int main(int argc, const char * const argv[]) and *init_process(int
> > *argc, const char * const * *argv) functions.
>
> That's good.
>
> > 4. Then I added -finstrument-functions in the configure file (Line number
> > 2830) in the extracted httpd-2.4.7 directory, full line below
> > ac_compile='$CC -c $CFLAGS -finstrument-functions $CPPFLAGS
> > conftest.$ac_ext >&5'
>
> As Suchakra said, -finstrument-functions is not related. You can use
> it later if you want, but let's leave it out for now. Also, if you
> want to add compilation flags like this, pass them at configure time.
> Also, _never_ change generated files (such as the configure script of
> Makefiles). They are way too complicated for a human and will get
> overwritten anyway. Instead, you should modify the configure.in or
> Makefile.in files, in this case. To add a compilation flag, you could
> do:
>
> $ ./configure CFLAGS="-finstrument-function"
>
> > 5. Then, from the /httpd-2.4.7 directory, I ran the following command to
> > configure the installation, it completed without any error.
> > ./configure --libdir=/usr/lib/usr/lib/liblttng-ust.so
> > --with-included-apr
>
> This is wrong. --libdir is used to tell autotools in which directory
> to install the compiled libraries. ./configure --with-included-apr is
> sufficient.
>
> > 6. When I ran the command 'make', I get the following error after a while
> > ...
> > make[1]: Entering directory `/root/httpd-2.4.7'
> > /root/httpd-2.4.7/srclib/apr/libtool --silent --mode=compile gcc
> -std=gnu99
> > -g -O2 -pthread -DLINUX -D_REENTRANT -D_GNU_SOURCE -I.
> > -I/root/httpd-2.4.7/os/unix -I/root/httpd-2.4.7/include
> > -I/root/httpd-2.4.7/srclib/apr/include
> > -I/root/httpd-2.4.7/srclib/apr-util/include
> > -I/root/httpd-2.4.7/srclib/apr-util/xml/expat/lib
> > -I/root/httpd-2.4.7/modules/aaa -I/root/httpd-2.4.7/modules/cache
> > -I/root/httpd-2.4.7/modules/core -I/root/httpd-2.4.7/modules/database
> > -I/root/httpd-2.4.7/modules/filters -I/root/httpd-2.4.7/modules/ldap
> > -I/root/httpd-2.4.7/modules/loggers -I/root/httpd-2.4.7/modules/lua
> > -I/root/httpd-2.4.7/modules/proxy -I/root/httpd-2.4.7/modules/session
> > -I/root/httpd-2.4.7/modules/ssl -I/root/httpd-2.4.7/modules/test
> > -I/root/httpd-2.4.7/server -I/root/httpd-2.4.7/modules/arch/unix
> > -I/root/httpd-2.4.7/modules/dav/main
> -I/root/httpd-2.4.7/modules/generators
> > -I/root/httpd-2.4.7/modules/mappers -prefer-non-pic -static -c
> modules.c &&
> > touch modules.lo
> > gcc -std=gnu99 -g -O2 -pthread -DLINUX -D_REENTRANT -D_GNU_SOURCE
> > -I. -I/root/httpd-2.4.7/os/unix -I/root/httpd-2.4.7/include
> > -I/root/httpd-2.4.7/srclib/apr/include
> > -I/root/httpd-2.4.7/srclib/apr-util/include
> > -I/root/httpd-2.4.7/srclib/apr-util/xml/expat/lib
> > -I/root/httpd-2.4.7/modules/aaa -I/root/httpd-2.4.7/modules/cache
> > -I/root/httpd-2.4.7/modules/core -I/root/httpd-2.4.7/modules/database
> > -I/root/httpd-2.4.7/modules/filters -I/root/httpd-2.4.7/modules/ldap
> > -I/root/httpd-2.4.7/modules/loggers -I/root/httpd-2.4.7/modules/lua
> > -I/root/httpd-2.4.7/modules/proxy -I/root/httpd-2.4.7/modules/session
> > -I/root/httpd-2.4.7/modules/ssl -I/root/httpd-2.4.7/modules/test
> > -I/root/httpd-2.4.7/server -I/root/httpd-2.4.7/modules/arch/unix
> > -I/root/httpd-2.4.7/modules/dav/main
> -I/root/httpd-2.4.7/modules/generators
> > -I/root/httpd-2.4.7/modules/mappers -c
> /root/httpd-2.4.7/server/buildmark.c
> > /root/httpd-2.4.7/srclib/apr/libtool --silent --mode=link gcc -std=gnu99
> -g
> > -O2 -pthread -o httpd modules.lo buildmark.o -export-dynamic
> > server/libmain.la modules/core/libmod_so.la modules/http/libmod_http.la
> > server/mpm/event/libevent.la os/unix/libos.la-L/usr/lib/x86_64-linux-gnu
> > -lpcre /root/httpd-2.4.7/srclib/apr-util/libaprutil-1.la
> > /root/httpd-2.4.7/srclib/apr-util/xml/expat/libexpat.la
> > /root/httpd-2.4.7/srclib/apr/libapr-1.la -luuid -lrt -lcrypt -lpthread
> -ldl
> > server/.libs/libmain.a(main.o): In function `main':
> > /root/httpd-2.4.7/server/main.c:443: undefined reference to
> > `__tracepoint_mk___apache_process_entry'
> > server/.libs/libmain.a(main.o): In function `init_process':
> > /root/httpd-2.4.7/server/main.c:284: undefined reference to
> > `__tracepoint_mk___apache_process_entry'
> > server/.libs/libmain.a(main.o): In function
> > `__tracepoint_cb_mk___apache_process_entry':
> > /root/httpd-2.4.7/server/smallestTracePoint.h:13: undefined reference to
> > `tracepoint_dlopen'
> > /root/httpd-2.4.7/server/smallestTracePoint.h:13: undefined reference to
> > `__tracepoint_mk___apache_process_entry'
> > /root/httpd-2.4.7/server/smallestTracePoint.h:13: undefined reference to
> > `tracepoint_dlopen'
> > /root/httpd-2.4.7/server/smallestTracePoint.h:13: undefined reference to
> > `tracepoint_dlopen'
> > /root/httpd-2.4.7/server/smallestTracePoint.h:13: undefined reference to
> > `tracepoint_dlopen'
> > /root/httpd-2.4.7/server/smallestTracePoint.h:13: undefined reference to
> > `__tracepoint_mk___apache_process_entry'
> > /root/httpd-2.4.7/server/smallestTracePoint.h:13: undefined reference to
> > `tracepoint_dlopen'
> > /root/httpd-2.4.7/server/smallestTracePoint.h:13: undefined reference to
> > `tracepoint_dlopen'
> > collect2: ld returned 1 exit status
> > make[1]: *** [httpd] Error 1
> > make[1]: Leaving directory `/root/httpd-2.4.7'
> > make: *** [all-recursive] Error 1
> >
> > I have tried including the smallestTracePoint.c file in the local
> makefile
> > (/root/httpd-2.4.7/MakeFile)... didn't do me any good.
> > Any idea what I am doing wrong ?
>
> That's right, you have to compile the .c file somewhere. I suggest you
> check where main.c is mentionned in a Makefile.in, and add
> smallestTracePoint.c there. Don't forget to re-run configure, and try
> to make again. This should get rid of the undefined references to
> __tracepoint_mk___apache_process_entry. For the other undefined
> references, it is because your tracepoint requires additional
> libraries, libdl and liblttng-ust. You should then add "-ldl
> -llttng-ust" to where the final executable is linked. When inspecting
> the build log, we see that this is done by the top-level Makefile, so
> we will go edit the top-level Makefile.in.
>
> (there might be a better place to put -ldl -llttng-ust, but it will do for
> now)
>
> Apache should now build with the tracepoint included.
>
> Then, doing
>
> $ lttng create
> $ lttng enable-event -u -a
> $ lttng start
> $ ./httpd
> (httpd complains about missing config file, but hits the tracepoint
> anyway)
> $ lttng stop
> $ lttng view
> ...
> [08:30:18.522789766] (+0.000173646) simark
> apache:apache_process_entry: { cpu_id = 2 }, { }
> ...
>
> Yay !
>
> I made a commit here to show the modifications I made to make it work:
>
> https://github.com/simark/httpd/commit/2c6d73c47156350233b346e9eaa49ffb07a58e6e
>
> Hopefully this can help you get started. Iif you instrument apache in
> an interesting/useful way, feel free to share your work, it could be
> useful for others!
>
> Simon
>
> >
> > LTTng version on the instance: 2.4.0-rc2 - Époque Opaque
> >
> > Linux Distribution: Ubuntu 12.04.3 LTS
> >
> >
> > Thanks,
> >
> >
> > --
> > Mehran
> >
> >
> > _______________________________________________
> > lttng-dev mailing list
> > lttng-dev at lists.lttng.org
> > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> >
>
--
-M.K.
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