Too many rcuos and rcuob processes in my VM

Question

I am running CentOS 7.2 (3.10.0-327.18.2.el7.x86_64) as VMware guest with 2 cpu and 6 GB RAM on my Lenevo W540 iCore 7 having 32 GB RAM.

I see 128 processes each for rcuos and rcuob in my VM. This does not sound right as these processes should be equal to number of cores in a system.

I am noticing my VM freeze occasionally.

Is there a way to limit the number of rcuos and rcuob processes equal to number of CPUs.

I reduced number of CPU in VM Guest to 1 and still the number of rcuos and rcuob are 128 each.

I then added maxcpus=0 as a kernel boot parameter and that reduced the number of rcuos and rcuob to 1 each but then I need more cores assigned to the VM. My application performance reduces by 40% if I just use one core.

Solution

My knowledge about Linux Kernel is very limited and and how to tweak it. I kept googling after I posted and stumbled upon another kernel boot parameter nr_cpus here and after I set this to 2 (Number of CPUs) in my VM, I now only see 2 rcuos and rcuoc processes.

This is what worked for me.

Edit

/etc/default/grub

nr_cpus=2

grub2-mkconfig -o /boot/grub2/grub.cfg

$ ps aux | grep rcu
root         8  0.0  0.0      0     0 ?        S    23:04   0:00 [rcu_bh]
root         9  0.0  0.0      0     0 ?        S    23:04   0:00 [rcuob/0]
root        10  0.0  0.0      0     0 ?        S    23:04   0:00 [rcuob/1]
root        11  0.0  0.0      0     0 ?        R    23:04   0:00 [rcu_sched]
root        12  0.0  0.0      0     0 ?        S    23:04   0:00 [rcuos/0]
root        13  0.0  0.0      0     0 ?        S    23:04   0:00 [rcuos/1]