rcu: Distinguish "rcuo" kthreads by RCU flavor

Currently, the per-no-CBs-CPU kthreads are named "rcuo" followed by
the CPU number, for example, "rcuo".  This is problematic given that
there are either two or three RCU flavors, each of which gets a per-CPU
kthread with exactly the same name.  This commit therefore introduces
a one-letter abbreviation for each RCU flavor, namely 'b' for RCU-bh,
'p' for RCU-preempt, and 's' for RCU-sched.  This abbreviation is used
to distinguish the "rcuo" kthreads, for example, for CPU 0 we would have
"rcuob/0", "rcuop/0", and "rcuos/0".

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4609e81dbc37..a17ba16c8fc8 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2461,9 +2461,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         In kernels built with CONFIG_RCU_NOCB_CPU=y, set
                         the specified list of CPUs to be no-callback CPUs.
                         Invocation of these CPUs' RCU callbacks will
-                        be offloaded to "rcuoN" kthreads created for
-                        that purpose.  This reduces OS jitter on the
+                        be offloaded to "rcuox/N" kthreads created for
+                        that purpose, where "x" is "b" for RCU-bh, "p"
+                        for RCU-preempt, and "s" for RCU-sched, and "N"
+                        is the CPU number.  This reduces OS jitter on the
                         offloaded CPUs, which can be useful for HPC and
+
                         real-time workloads.  It can also improve energy
                         efficiency for asymmetric multiprocessors.