linux-kernel - Re: [PATCH] mm: compaction: some tracepoints should be defined only when CONFIG

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Date:   Wed, 13 Mar 2019 00:29:57 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        Souptick Joarder <jrdr.linux@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, shaoyafang@...iglobal.com
Subject: Re: [PATCH] mm: compaction: some tracepoints should be defined only
 when CONFIG_COMPACTION is set

On Wed, Mar 13, 2019 at 12:18 AM Michal Hocko <mhocko@...nel.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.

That's an improvement.

> > Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> > ---
> >  include/trace/events/compaction.h | 6 ++----
> >  1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h
> > index 6074eff..3e42078 100644
> > --- a/include/trace/events/compaction.h
> > +++ b/include/trace/events/compaction.h
> > @@ -64,6 +64,7 @@
> >       TP_ARGS(start_pfn, end_pfn, nr_scanned, nr_taken)
> >  );
> >
> > +#ifdef CONFIG_COMPACTION
> >  TRACE_EVENT(mm_compaction_migratepages,
> >
> >       TP_PROTO(unsigned long nr_all,
> > @@ -132,7 +133,6 @@
> >               __entry->sync ? "sync" : "async")
> >  );
> >
> > -#ifdef CONFIG_COMPACTION
> >  TRACE_EVENT(mm_compaction_end,
> >       TP_PROTO(unsigned long zone_start, unsigned long migrate_pfn,
> >               unsigned long free_pfn, unsigned long zone_end, bool sync,
> > @@ -166,7 +166,6 @@
> >               __entry->sync ? "sync" : "async",
> >               __print_symbolic(__entry->status, COMPACTION_STATUS))
> >  );
> > -#endif
> >
> >  TRACE_EVENT(mm_compaction_try_to_compact_pages,
> >
> > @@ -195,7 +194,6 @@
> >               __entry->prio)
> >  );
> >
> > -#ifdef CONFIG_COMPACTION
> >  DECLARE_EVENT_CLASS(mm_compaction_suitable_template,
> >
> >       TP_PROTO(struct zone *zone,
> > @@ -296,7 +294,6 @@
> >
> >       TP_ARGS(zone, order)
> >  );
> > -#endif
> >
> >  TRACE_EVENT(mm_compaction_kcompactd_sleep,
> >
> > @@ -352,6 +349,7 @@
> >
> >       TP_ARGS(nid, order, classzone_idx)
> >  );
> > +#endif
> >
> >  #endif /* _TRACE_COMPACTION_H */
> >
> > --
> > 1.8.3.1
> >
>
> --
> Michal Hocko
> SUSE Labs