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Date:   Thu, 3 Mar 2022 10:40:48 +0800
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Subject: Re: [PATCH] sched/numa: add per-process numa_balancing
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Cc:     songmuchun@bytedance.com, zhengqi.arch@bytedance.com,
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References: <20220224075227.27127-1-ligang.bdlg@bytedance.com>
From:   Gang Li <ligang.bdlg@bytedance.com>
To:     Peter Zijlstra <peterz@infradead.org>, Mel Gorman <mgorman@suse.de>
In-Reply-To: <20220224075227.27127-1-ligang.bdlg@bytedance.com>
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Hi Peter Zijlstra,

On 2022/1/12 22:43, Peter Zijlstra wrote:
 >> 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:
 >> 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/
[2] Link: https://lore.kernel.org/lkml/20211118085819.GD3301@suse.de/
-- 
Thanks
Gang Li