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c03be752d3
Joel Fernandes found that the synchronize_rcu_tasks() was taking a significant amount of time. He demonstrated it with the following test: # cd /sys/kernel/tracing # while [ 1 ]; do x=1; done & # echo '__schedule_bug:traceon' > set_ftrace_filter # time echo '!__schedule_bug:traceon' > set_ftrace_filter; real 0m1.064s user 0m0.000s sys 0m0.004s Where it takes a little over a second to perform the synchronize, because there's a loop that waits 1 second at a time for tasks to get through their quiescent points when there's a task that must be waited for. After discussion we came up with a simple way to wait for holdouts but increase the time for each iteration of the loop but no more than a full second. With the new patch we have: # time echo '!__schedule_bug:traceon' > set_ftrace_filter; real 0m0.131s user 0m0.000s sys 0m0.004s Which drops it down to 13% of what the original wait time was. Link: http://lkml.kernel.org/r/20180523063815.198302-2-joel@joelfernandes.org Reported-by: Joel Fernandes (Google) <joel@joelfernandes.org> Suggested-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
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| .. | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||
| rcu.h | ||
| rcu_segcblist.c | ||
| rcu_segcblist.h | ||
| rcuperf.c | ||
| rcutorture.c | ||
| srcutiny.c | ||
| srcutree.c | ||
| sync.c | ||
| tiny.c | ||
| tree.c | ||
| tree.h | ||
| tree_exp.h | ||
| tree_plugin.h | ||
| update.c | ||