linux-kernel - Re: [PATCH v2 4/5] mm/compaction: more trace to understand when/why compaction start/finish

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Date:	Tue, 13 Jan 2015 16:16:05 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/5] mm/compaction: more trace to understand when/why
 compaction start/finish

On Mon, Jan 12, 2015 at 04:53:53PM +0100, Vlastimil Babka wrote:
> On 01/12/2015 09:21 AM, Joonsoo Kim wrote:
> > It is not well analyzed that when/why compaction start/finish or not. With
> > these new tracepoints, we can know much more about start/finish reason of
> > compaction. I can find following bug with these tracepoint.
> > 
> > http://www.spinics.net/lists/linux-mm/msg81582.html
> > 
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
> > ---
> >  include/linux/compaction.h        |    3 ++
> >  include/trace/events/compaction.h |   94 +++++++++++++++++++++++++++++++++++++
> >  mm/compaction.c                   |   41 ++++++++++++++--
> >  3 files changed, 134 insertions(+), 4 deletions(-)
> > 
> > diff --git a/include/linux/compaction.h b/include/linux/compaction.h
> > index a9547b6..d82181a 100644
> > --- a/include/linux/compaction.h
> > +++ b/include/linux/compaction.h
> > @@ -12,6 +12,9 @@
> >  #define COMPACT_PARTIAL		3
> >  /* The full zone was compacted */
> >  #define COMPACT_COMPLETE	4
> > +/* For more detailed tracepoint output */
> > +#define COMPACT_NO_SUITABLE_PAGE	5
> > +#define COMPACT_NOT_SUITABLE_ZONE	6
> >  /* When adding new state, please change compaction_status_string, too */
> >  
> >  /* Used to signal whether compaction detected need_sched() or lock contention */
> > diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h
> > index 139020b..839dd4f 100644
> > --- a/include/trace/events/compaction.h
> > +++ b/include/trace/events/compaction.h
> > @@ -164,6 +164,100 @@ TRACE_EVENT(mm_compaction_end,
> >  		compaction_status_string[__entry->status])
> >  );
> >  
> > +TRACE_EVENT(mm_compaction_try_to_compact_pages,
> > +
> > +	TP_PROTO(
> > +		int order,
> > +		gfp_t gfp_mask,
> > +		enum migrate_mode mode,
> > +		int alloc_flags,
> > +		int classzone_idx),
> 
> I wonder if alloc_flags and classzone_idx is particularly useful. It affects the
> watermark checks, but those are a bit of blackbox anyway.

Yes, I think so. How about printing gfp_flag rather than these? It would
tell us migratetype and other information so would be useful.

Thanks.
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