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From:   Yafang Shao <laoar.shao@gmail.com>
Date:   Wed, 13 Mar 2019 00:48:05 +0800
Message-ID: <CALOAHbC5+YJR6BYLCz+-8xPhZPczqnaKv-rZ97tF+traPTut0A@mail.gmail.com>
Subject: Re: [PATCH] mm: compaction: some tracepoints should be defined only
 when CONFIG_COMPACTION is set
To:     Michal Hocko <mhocko@kernel.org>
Cc:     Vlastimil Babka <vbabka@suse.cz>,
        Souptick Joarder <jrdr.linux@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>, shaoyafang@didiglobal.com
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On Wed, Mar 13, 2019 at 12:44 AM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Wed 13-03-19 00:29:57, Yafang Shao wrote:
> > On Wed, Mar 13, 2019 at 12:18 AM Michal Hocko <mhocko@kernel.org> wrote:
> > >
> > > On Sat 02-03-19 12:38:58, Yafang Shao wrote:
> > > > Only mm_compaction_isolate_{free, migrate}pages may be used when
> > > > CONFIG_COMPACTION is not set.
> > > > All others are used only when CONFIG_COMPACTION is set.
> > >
> > > Why is this an improvement?
> > >
> >
> > After this change, if CONFIG_COMPACTION is not set, the tracepoints
> > that only work when CONFIG_COMPACTION is set will not be exposed to
> > the usespace.
> > Without this change, they will always be expose in debugfs no matter
> > CONFIG_COMPACTION is set or not.
>
> And this is exactly something that the changelog should mention. I
> wasn't aware that we do export tracepoints even when they are not used
> by any code path. This whole macro based programming is just a black
> magic.
> --

Sure, I will modify the changelog and send v2.

Thanks
Yafang