GAB timer only wakes up a thread that does the real work. If either the operating system did not get a chance to schedule the thread or the operating system did not fire the timer itself, then GAB might log a message similar to the following:

GAB INFO V-15-1-20124 timer not called for 11 seconds

Recommended Action: If this issue occurs rarely at times of high load, and does not cause any detrimental effects, the issue is benign. If the issue recurs, or if the issue causes repeated VCS daemon restarts or node panics, you must increase the priority of the thread (gab_timer_pri tunable parameter).

See About GAB load-time or static tunable parameters.