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

Joonsoo Kim
2015-01-13T07:15:40Z

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@lge.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.