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Date:   Mon, 6 Sep 2021 08:37:04 +0200
From:   Michal Hocko <mhocko@suse.com>
To:     yong w <yongw.pur@gmail.com>
Cc:     Tejun Heo <tj@kernel.org>, Jonathan Corbet <corbet@lwn.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Shakeel Butt <shakeelb@google.com>,
        Roman Gushchin <guro@fb.com>, alexs@kernel.org,
        Wei Yang <richard.weiyang@gmail.com>, Hui Su <sh_def@163.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        wang.yong12@zte.com.cn, Cgroups <cgroups@vger.kernel.org>,
        linux-doc@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>, yang.yang29@zte.com.cn
Subject: Re: [PATCH v2] mm: Add configuration to control whether vmpressure
 notifier is enabled
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On Sat 04-09-21 18:41:00, yong w wrote:
[..]
> > It is not in conflict but runtime overhead reduction without more burden
> > on the configurability is usually a preferred approach.
> I agree with you.I had an idea that we use global variables to identify whether
> there is event registration,however, global variables need to be
> protected with locks.

Have a look at static keys which are usual tool to provide effectivelly
zero overhead disabled branch.
-- 
Michal Hocko
SUSE Labs