From Buzztard

This page is about ideas of how to optimize ressource usage of linux apps.

[edit] Linking

[edit] --as-needed flag

see discussion about --as-needed flag

[edit] elf visibility

see GCC and elf visibility

[edit] Analysing

[edit] strace

strace is a good too to check whats going on. Here are two examples:

strace -e trace=file 2>trace.log.0003 ./bt-cmd --command=info --input-file=../share/buzztard/songs/simple2.xml
strace -c 2>trace.sum.0003 ./bt-cmd --command=info --input-file=../share/buzztard/songs/simple2.xml

Additionally we can use strace together with plot-timeline.py:

strace -ttt -f -o /tmp/logfile.strace my-program
plot-timeline.py -o prettygraph.png /tmp/logfile.strace

We can also test if bt-edit operates tickless (which it doesn't yet, because of the cpu-monitor),

strace -ttt -e poll -p `pidof bt-edit`

[edit] oprofile

To collect data run

opcontrol --reset
opcontrol --start
<run programm>
opcontrol --stop
opcontrol --dump

opcontrol --shutdown

To analyse profiling data:

opreport -l | head -n20
opreport -l /home/ensonic/lib/libx* | head -n20
opannotate --source --output-dir=/home/ensonic/temp/libx /home/ensonic/lib/libx*

[edit] Memory usage

[edit] use g_alloca

Alloca reserves memory on the stack. It is a bit more tedious to handle (maybe we can wrap it up in a macro), but has several advantages. It only works if we just temporaily need the space. Advantages are

• its fast
• we don't need to free the stuff
• it does not fragment memory space

Instead of doing:

gchar *status=g_strdup_printf(_("Loading file \"%s\""),file_name);
g_object_set(G_OBJECT(self),"status",status,NULL);
g_free(status);

do it like below:

gchar *status=g_alloca(strlen(_("Loading file \"%s\""))+strlen(file_name)-1);
g_sprintf(status,_("Loading file \"%s\""),file_name);
g_object_set(G_OBJECT(self),"status",status,NULL);

It is not trivial to write it as a macro, as it needs to figure the length of the result string.