lib: Convert RUSAGE_SELF to RUSAGE_THREAD where we can
When using getrusage, we have multiple choices about what
to call for data gathering about this particular thread of execution.
RUSAGE_SELF -> This means gather all cpu run time for all pthreads associated
with this process.
RUSAGE_THREAD -> This means gather all cpu run time for this particular
pthread.
Clearly with data gathering for slow thread as well as `show thread cpu`
it would be preferable to gather only data about the current running
pthread. This probably was the original behavior of using RUSAGE_SELF
when we didn't have multiple pthreads. So it didn't matter so much.
Prior to this change, 10 iterations of 1 million routes install/remove
from zebra would give us this cpu time for the dataplane pthread:
Showing statistics for pthread Zebra dplane thread
--------------------------------------------------
CPU (user+system): Real (wall-clock):
Active Runtime(ms) Invoked Avg uSec Max uSecs Avg uSec Max uSecs Type Thread
0 280902.149 326541 860
2609982 550
2468910 E dplane_thread_loop
After this change we are seeing this:
Showing statistics for pthread Zebra dplane thread
--------------------------------------------------
CPU (user+system): Real (wall-clock):
Active Runtime(ms) Invoked Avg uSec Max uSecs Avg uSec Max uSecs Type Thread
0 58045.560 334944 173 277226 539
2502268 E dplane_thread_loop
Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>