The kworker workqueue kthreads can also contribute to OS jitter.
The amount of jitter depends on their use, so this commit adds
documentation on avoiding OS jitter due to workqueue use.
Reported-by: Jonathan Clairembault <jonathan.clairembault@novasparks.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The Linux kernel uses a number of per-CPU kthreads, any of which might
contribute to OS jitter at any time. The usual approach to normal
kthreads, namely to bind them to a "housekeeping" CPU, does not work
with these kthreads because they cannot operate correctly if moved to
some other CPU. This commit therefore lists ways of controlling OS
jitter from the Linux kernel's per-CPU kthreads. It also lists some
ways of diagnosing excessive jitter.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Olivier Baetz <olivier.baetz@novasparks.com>
Cc: Pradeep Satyanarayana <pradeeps@linux.vnet.ibm.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
