Re: [PATCH 1/2] sched/numa: Add ability to override task's numa_preferred_nid.

[Madadi Vineeth Reddy <vineethr@linux.ibm.com>]

Hi Chris,

On 15/04/25 07:05, Chris Hyser wrote:
> From: chris hyser <chris.hyser@oracle.com>
> 

[..snip..]

> The following results were from TPCC runs on an Oracle Database. The system
> was a 2-node Intel machine with a database running on each node with local
> memory allocations. No tasks or memory were pinned.
> 
> There are four scenarios of interest:
> 
> - Auto NUMA Balancing OFF.
>     base value
> 
> - Auto NUMA Balancing ON.
>     1.2% - ANB ON better than ANB OFF.
> 
> - Use the prctl(), ANB ON, parameters set to prevent faulting.
>     2.4% - prctl() better then ANB OFF.
>     1.2% - prctl() better than ANB ON.
> 
> - Use the prctl(), ANB parameters normal.
>     3.1% - prctl() and ANB ON better than ANB OFF.
>     1.9% - prctl() and ANB ON better than just ANB ON.
>     0.7% - prctl() and ANB ON better than prctl() and ANB ON/faulting off
> 

Are you using prctl() to set the preferred node id for all the tasks of your run?
If yes, then how `prctl() and ANB ON better than prctl() and ANB ON/faulting off`
case happens?

IIUC, when setting preferred node in numa_preferred_nid_force, the original
numa_preferred_nid which is derived from page faults will be a nop which should
be an overhead.

Let me know if my understanding is correct. Also, can you tell how to set the
parameters of ANB to prevent faulting.

Thanks,
Madadi Vineeth Reddy

> In benchmarks pinning large regions of heavily accessed memory, the
> advantages of the prctl() over Auto NUMA Balancing alone is significantly
> higher.
> 
> Signed-off-by: Chris Hyser <chris.hyser@oracle.com>

[..snip..]