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Wed, 02 Mar 2022 18:40:54 -0800 (PST) Message-ID: Date: Thu, 3 Mar 2022 10:40:48 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [PATCH] sched/numa: add per-process numa_balancing Content-Language: en-US Cc: songmuchun@bytedance.com, zhengqi.arch@bytedance.com, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org References: <20220224075227.27127-1-ligang.bdlg@bytedance.com> From: Gang Li To: Peter Zijlstra , Mel Gorman In-Reply-To: <20220224075227.27127-1-ligang.bdlg@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: DC90D120005 X-Rspam-User: Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=WkDu5aHP; spf=pass (imf29.hostedemail.com: domain of ligang.bdlg@bytedance.com designates 209.85.216.53 as permitted sender) smtp.mailfrom=ligang.bdlg@bytedance.com; dmarc=pass (policy=none) header.from=bytedance.com X-Stat-Signature: os4y1dm336b5urjxyyb4rspiipdxjnqq X-HE-Tag: 1646275255-91426 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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