Hi Team,

How to disable multi threading in redhat linux 7 which is hosted in aws?

I followed the below blog, but no luck.Could you please help with this.

https://www.golinuxhub.com/2018/01/h...ble-hyper.html

Thanks,
Bala

In AWS, you have virtual servers. The servers are pieces of cpu, or a cpu usually. Multi threading enables a process to run code at the same time. I do not see why you would want to go single thread. It would be like asking for a text screen that only shows 1 line of text. Why do you want to disable it? I think aws mini/micro is 1 cpu, and during the server build determines how many cpus you get.

"no luck" doesn't tell us what didn't work for you.
If you're using RHEL, you should use RedHat support for help.

Please expand on "no luck"

Hi,

I have 16 CPU's with 8 cores running 2 threads each. Now i would like to have my system to have 8 CPU where each core use only 1 thread.

I disabled it, but after rebooting the server, the changes are not reflecting.Need some help in making the changes permanent?

echo 0 > /sys/devices/system/cpu/cpu8/online
echo 0 > /sys/devices/system/cpu/cpu9/online
echo 0 > /sys/devices/system/cpu/cpu10/online
echo 0 > /sys/devices/system/cpu/cpu11/online
echo 0 > /sys/devices/system/cpu/cpu12/online
echo 0 > /sys/devices/system/cpu/cpu13/online
echo 0 > /sys/devices/system/cpu/cpu14/online
echo 0 > /sys/devices/system/cpu/cpu15/online

Thanks,
Bala

In the link you posted there is a section "Disable HT permanently"
What there do you need help with?

1 members found this post helpful.

That did not worked actually... Hence started a thread here.

Again, what did not work? What did you actually try?

I followed exactly what was mentioned in the blog.. Made the changes in grub file and ran grub2-mkconfig command.. After that rebooted the server, whatever changes I made was vanished.. System was using 16 CPUs again

There is this:
emphasis added...

I'm guessing you don't have access to the BIOS on that VPS...is that correct?

Yes, I dont have access nor I don't know how to do it. it is hosted in aws(virtual server).I just have root access

So how to make this change permanently?

If it's controlled in the BIOS, and you don't have access to the BIOS, you can't make it permanent, per the "IMPORTANT NOTE" from those instructions.

Perhaps you need to write a script to implement it at boot time.

But as wondered about in #2, why do you even want to disable it?

1 members found this post helpful.

Thanks for all ur time to spend on this. If I find a way to disable it permanently, will let u know.. For time being my client want multi threading to be disabled in the server. Will let you know in brief once I get to know abt it.. Thanks again.

Why would they want this? I'm guessing it's the client's reaction to the security problems that have made the headlines where Intel and AMD chips (if I understand the problem) can allow parallel threads to peek into parts of the CPU that other threads are running on and, somehow, obtain data they shouldn't be able to see. I thought Red Hat and others had mitigated that problem with kernel patches.

1 members found this post helpful.

Could be, in which case the OP (or the client) should contact Red Hat support, as previously suggested, to determine if the solution they seek is even necessary.

Hi All,

Performance is better when we disable multi threading,hence client wants to disable it.

Followed the below steps to disable multi-threading in RHEL7.

1. Add the nr_cpus=N parameter to the “GRUB_CMDLINE_LINUX” line in “/etc/sysconfig/grub”
2. Run grub2-mkconfig -o /boot/grub2/grub.cfg
3. Reboot the server.

Thanks,
Bala