Re: [PATCH] sched/numa: add per-process numa_balancing

Hi Peter Zijlstra,

On 2022/1/12 22:43, Peter Zijlstra wrote:

quoted

Set per-process numa balancing:
	prctl(PR_NUMA_BALANCING, PR_SET_NUMAB_DISABLE); //disable
	prctl(PR_NUMA_BALANCING, PR_SET_NUMAB_ENABLE);  //enable
	prctl(PR_NUMA_BALANCING, PR_SET_NUMAB_DEFAULT); //follow global

This seems to imply you can prctl(ENABLE) even if the global is
disabled, IOW sched_numa_balancing is off.

I have discussed the semantics of this API with Mel Gorman, we both
agree that we can prctl(ENABLE) even if the global is disabled.

On 2021/11/10 00:26, Mel Gorman wrote: [1]

For symmetry and consistency of the tuning. Either there is per-process
control or there is not. Right now, there is only the ability to turn
off NUMA balancing via prctl if globally enabled. There is no option to
turn NUMA balancing on for a single task if globally disabled.

On 11/18/21 4:58 PM, Mel Gorman wrote: [2]

On Thu, Nov 18, 2021 at 11:26:30AM +0800, Gang Li wrote:

quoted

3. prctl(PR_NUMA_BALANCING, PR_SET_NUMAB_ENABLE);  //enable

If PR_SET_NUMAB_ENABLE enables numa balancing for a task when
kernel.numa_balancing == 0 instead of returning an error then sure.

[1] Link: https://lore.kernel.org/lkml/20211109162647.GY3891@suse.de/ (local)
[2] Link: https://lore.kernel.org/lkml/20211118085819.GD3301@suse.de/ (local)
-- 
Thanks
Gang Li