Re: Is it possible to disable numa_balance after boot?

[Andi Kleen <andi@firstfloor.org>]

On Sat, Jan 04, 2014 at 06:46:55PM +0100, Andreas Hollmann wrote:
> Hi,
> 
> is possible to turn of numa balancing (introduced in 3.8) in a running kernel?


I submitted a patch to do it some time ago

https://lkml.org/lkml/2013/4/24/529

But it didn't seem to have made it in. Andrew? Mel?

Yes I agree a disable switch is totally needed for such an intrusive
feature, if only to isolate problems with it.

-Andi


> 
> I'm running a recent arch kernel and numa balancing is enabled by
> default. I checked
> several documents and found some sysctl variable which influence the behavior of
> numa balance, but there is no clear documentation if it's possible to
> disable it.
> 
> The only defined way to disable it is using a kernel parameter
> 
> numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
> Allowed values are enable and disable
> 
> Is there any other way?
> 
> Best regards,
> Andreas
> 
> 
> $ uname -a
> Linux inwest 3.12.6-1-ARCH #1 SMP PREEMPT Fri Dec 20 19:39:00 CET 2013
> x86_64 GNU/Linux
> 
> $ cat /usr/src/linux-3.12.6-1-ARCH/.config | grep NUMA_BALANCING
> CONFIG_ARCH_SUPPORTS_NUMA_BALANCING=y
> CONFIG_NUMA_BALANCING_DEFAULT_ENABLED=y
> CONFIG_NUMA_BALANCING=y
> 
> $ ls -l /proc/sys/kernel | grep numa_bal
> -rw-r--r-- 1 root root 0 Jan  4 14:23 numa_balancing_scan_delay_ms
> -rw-r--r-- 1 root root 0 Jan  4 14:23 numa_balancing_scan_period_max_ms
> -rw-r--r-- 1 root root 0 Jan  4 14:23 numa_balancing_scan_period_min_ms
> -rw-r--r-- 1 root root 0 Jan  4 14:23 numa_balancing_scan_period_reset
> -rw-r--r-- 1 root root 0 Jan  4 14:23 numa_balancing_scan_size_mb
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-- 
ak@linux.intel.com -- Speaking for myself only.