v5 --> v6:
1. Frist, update patch 1/2, so that, CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y takes
effect only when there are no 'rcu_nocbs=' and 'nohz_full='. Retain the same
semantics as the original.
2. Then, add patch 2/2, so that, CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y takes effect
as long as there is no "rcu_nocbs=" boot parameter. This is suggested by
Frederic Weisbecker.
Test cases and test results as below:
----------------------------------------------------------------------
| CONFIG_NO_HZ_FULL | CONFIG_RCU_NOCB_CPU_DEFAULT_ALL | cmdline |
----------------------------------------------------------------------
1) N | N | none |
2) N | N | rcu_nocbs=1-2 |
3) Y | N | nohz_full=2-3 |
4) Y | N | rcu_nocbs=1 nohz_full=3 |
5) Y | Y | none |
6) Y | Y | rcu_nocbs=1-2 |
7) Y | Y | nohz_full=2-3 |
8) Y | Y | rcu_nocbs=1 nohz_full=3 |
----------------------------------------------------------------------
dmesg | grep "Offload RCU callbacks"
1) none
2) Offload RCU callbacks from CPUs: 1-2.
3) Offload RCU callbacks from CPUs: 2-3.
4) Offload RCU callbacks from CPUs: 1,3.
5) Offload RCU callbacks from CPUs: 0-3.
6) Offload RCU callbacks from CPUs: 1-2.
7) Offload RCU callbacks from CPUs: 0-3.
8) Offload RCU callbacks from CPUs: 1,3.
v4 --> v5:
1. Cancel eliminate rcu_state.nocb_is_setup. It is useful for case 1) below.
Test cases and test results as below:
----------------------------------------------------------------------
| CONFIG_NO_HZ_FULL | CONFIG_RCU_NOCB_CPU_DEFAULT_ALL | cmdline |
----------------------------------------------------------------------
1) N | N | none |
2) N | N | rcu_nocbs=1-2 |
3) Y | N | nohz_full=1-2 |
4) Y | Y | none |
----------------------------------------------------------------------
1)
[ 1018.082417] rcu-torture:--- End of test: SUCCESS (default)
root@genericarmv8:~# dmesg | grep "Offload RCU callbacks"
root@genericarmv8:~# zcat /proc/config.gz | grep NOCB
CONFIG_RCU_NOCB_CPU=y
# CONFIG_RCU_NOCB_CPU_DEFAULT_ALL is not set
root@genericarmv8:~# zcat /proc/config.gz | grep NO_HZ_FULL
# CONFIG_NO_HZ_FULL is not set
root@genericarmv8:~# cat /proc/cmdline
console=ttyS0 earlyprintk=serial root=/dev/sda rw
2) 3) 4)
The same to v4.
v3 --> v4:
Fix a build warning.
- struct cpumask *cpumask = NULL;
+ const struct cpumask *cpumask = NULL;
v2 --> v3:
1. Eliminate rcu_state.nocb_is_setup
2. Update the code based on the above patch and commit b37a667c6242
("rcu/nocb: Add an option to offload all CPUs on boot").
Test cases and test results as below:
----------------------------------------------------------------------
| CONFIG_NO_HZ_FULL | CONFIG_RCU_NOCB_CPU_DEFAULT_ALL | cmdline |
----------------------------------------------------------------------
1) N | N | none |
2) N | N | rcu_nocbs=1-2 |
3) Y | N | nohz_full=1-2 |
4) Y | Y | none |
----------------------------------------------------------------------
1)
[ 1085.691770] rcu-torture:--- End of test: SUCCESS: (default)
root@genericarmv8:~# dmesg | grep "Offload RCU callbacks"
[ 0.000000] rcu: Offload RCU callbacks from CPUs: (none).
root@genericarmv8:~# zcat /proc/config.gz | grep NOCB
CONFIG_RCU_NOCB_CPU=y
# CONFIG_RCU_NOCB_CPU_DEFAULT_ALL is not set
root@genericarmv8:~# zcat /proc/config.gz | grep NO_HZ_FULL
# CONFIG_NO_HZ_FULL is not set
root@genericarmv8:~# cat /proc/cmdline
console=ttyAMA0 root=/dev/vda2 crashkernel=256M@ee000000
2)
[ 1022.532198] rcu-torture:--- End of test: SUCCESS: (default)
root@genericarmv8:~# dmesg | grep "Offload RCU callbacks"
[ 0.000000] rcu: Offload RCU callbacks from CPUs: 1-2.
root@genericarmv8:~# zcat /proc/config.gz | grep NOCB
CONFIG_RCU_NOCB_CPU=y
# CONFIG_RCU_NOCB_CPU_DEFAULT_ALL is not set
root@genericarmv8:~# zcat /proc/config.gz | grep NO_HZ_FULL
# CONFIG_NO_HZ_FULL is not set
root@genericarmv8:~# cat /proc/cmdline
console=ttyAMA0 root=/dev/vda2 crashkernel=256M@ee000000 rcu_nocbs=1-2
3)
[ 1011.714712] rcu-torture:--- End of test: SUCCESS: (default)
root@genericarmv8:~# dmesg | grep "Offload RCU callbacks"
[ 0.000000] rcu: Offload RCU callbacks from CPUs: 1-2.
root@genericarmv8:~# zcat /proc/config.gz | grep NOCB
CONFIG_RCU_NOCB_CPU=y
# CONFIG_RCU_NOCB_CPU_DEFAULT_ALL is not set
root@genericarmv8:~# zcat /proc/config.gz | grep NO_HZ_FULL
CONFIG_NO_HZ_FULL=y
root@genericarmv8:~# cat /proc/cmdline
console=ttyAMA0 root=/dev/vda2 crashkernel=256M@ee000000 nohz_full=1-2
4)
[ 1031.047094] rcu-torture:--- End of test: SUCCESS: (default)
root@genericarmv8:~# dmesg | grep "Offload RCU callbacks"
[ 0.000000] rcu: Offload RCU callbacks from CPUs: 0-3.
root@genericarmv8:~# zcat /proc/config.gz | grep NOCB
CONFIG_RCU_NOCB_CPU=y
CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y
root@genericarmv8:~# zcat /proc/config.gz | grep NO_HZ_FULL
CONFIG_NO_HZ_FULL=y
root@genericarmv8:~# cat /proc/cmdline
console=ttyAMA0 root=/dev/vda2 crashkernel=256M@ee000000
v1 --> v2:
Update commit message.
Zhen Lei (2):
rcu: Simplify rcu_init_nohz() cpumask handling
rcu: Offload callback processing from all CPUs in the absence of
rcu_nocbs=
kernel/rcu/Kconfig | 4 ++--
kernel/rcu/tree_nocb.h | 35 ++++++++++++-----------------------
2 files changed, 14 insertions(+), 25 deletions(-)
--
2.25.1
