From fabcfe858d05e312dc7ba422a1c07dcfe8dccba7 Mon Sep 17 00:00:00 2001
From: Valentin Schneider <vschneid@redhat.com>
Date: Thu, 29 Sep 2022 13:43:47 +0100
Subject: [PATCH] realtime-virtual-*: Tune priority of new ktimers threads

The PREEMPT_RT upstream tree [1] is reintroducing a per-CPU kthread for
handling timer expiry named ktimers/${cpu}, and RHEL-RT is following this
approach [2].

The recommended priority tuning for that kthread is to simply match that of
ksoftirqd, which is what is implemented here.

Note that ktimersoftd is the predecessor of ktimers, and isn't present on
RT kernels newer than v5.0.19-rt11 / RHEL-RT 7.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
[2]: https://bugzilla.redhat.com/show_bug.cgi?id=2122220

Resolves: rhbz#2122220
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
---
 profiles/realtime-virtual-guest/tuned.conf | 3 ++-
 profiles/realtime-virtual-host/tuned.conf  | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/profiles/realtime-virtual-guest/tuned.conf b/profiles/realtime-virtual-guest/tuned.conf
index 78ad98d..a381f41 100644
--- a/profiles/realtime-virtual-guest/tuned.conf
+++ b/profiles/realtime-virtual-guest/tuned.conf
@@ -25,6 +25,7 @@ assert2=${f:assertion:isolated_cores contains online CPU(s):${isolated_cores_exp
 # group.group_name=rule_priority:scheduler_policy:scheduler_priority:core_affinity_in_hex:process_name_regex
 # for i in `pgrep ksoftirqd` ; do grep Cpus_allowed_list /proc/$i/status ; done
 group.ksoftirqd=0:f:2:*:^\[ksoftirqd
+group.ktimers=0:f:2:*:^\[ktimers
 
 # for i in `pgrep rcuc` ; do grep Cpus_allowed_list /proc/$i/status ; done
 group.rcuc=0:f:4:*:^\[rcuc
@@ -35,7 +36,7 @@ group.rcub=0:f:4:*:^\[rcub
 # for i in `pgrep ktimersoftd` ; do grep Cpus_allowed_list /proc/$i/status ; done
 group.ktimersoftd=0:f:3:*:^\[ktimersoftd
 
-ps_blacklist=^\[ksoftirqd;^\[rcuc;^\[rcub;^\[ktimersoftd
+ps_blacklist=^\[ksoftirqd;^\[ktimers;^\[rcuc;^\[rcub;^\[ktimersoftd
 
 [sysfs]
 # Perform lockless check for timer softirq on isolated CPUs.
diff --git a/profiles/realtime-virtual-host/tuned.conf b/profiles/realtime-virtual-host/tuned.conf
index 862469c..b0e8846 100644
--- a/profiles/realtime-virtual-host/tuned.conf
+++ b/profiles/realtime-virtual-host/tuned.conf
@@ -30,6 +30,7 @@ assert2=${f:assertion:isolated_cores contains online CPU(s):${isolated_cores_exp
 # group.group_name=rule_priority:scheduler_policy:scheduler_priority:core_affinity_in_hex:process_name_regex
 # for i in `pgrep ksoftirqd` ; do grep Cpus_allowed_list /proc/$i/status ; done
 group.ksoftirqd=0:f:2:*:^\[ksoftirqd
+group.ktimers=0:f:2:*:^\[ktimers
 
 # for i in `pgrep rcuc` ; do grep Cpus_allowed_list /proc/$i/status ; done
 group.rcuc=0:f:4:*:^\[rcuc
@@ -40,7 +41,7 @@ group.rcub=0:f:4:*:^\[rcub
 # for i in `pgrep ktimersoftd` ; do grep Cpus_allowed_list /proc/$i/status ; done
 group.ktimersoftd=0:f:3:*:^\[ktimersoftd
 
-ps_blacklist=^\[ksoftirqd;^\[rcuc;^\[rcub;^\[ktimersoftd;pmd;PMD;^DPDK;qemu-kvm
+ps_blacklist=^\[ksoftirqd;^\[ktimers;^\[rcuc;^\[rcub;^\[ktimersoftd;pmd;PMD;^DPDK;qemu-kvm
 
 [sysfs]
 # Stop kernel same page merge (KSM) daemon, it may introduce latencies.