linux-kernel - Re: [PATCH v2] mm: Add configuration to control whether vmpressure notifier is enabled

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Message-ID: <YTW3EMKU7fLl62bC@dhcp22.suse.cz>
Date:   Mon, 6 Sep 2021 08:37:04 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     yong w <yongw.pur@...il.com>
Cc:     Tejun Heo <tj@...nel.org>, Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Roman Gushchin <guro@...com>, alexs@...nel.org,
        Wei Yang <richard.weiyang@...il.com>, Hui Su <sh_def@....com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        wang.yong12@....com.cn, Cgroups <cgroups@...r.kernel.org>,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>, yang.yang29@....com.cn
Subject: Re: [PATCH v2] mm: Add configuration to control whether vmpressure
 notifier is enabled

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