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    SubjectRe: [PATCH] mm: compaction: Trace compaction begin and end
    On 12/04/2013 03:30 PM, Mel Gorman wrote:
    > This patch adds two tracepoints for compaction begin and end of a zone. Using
    > this it is possible to calculate how much time a workload is spending
    > within compaction and potentially debug problems related to cached pfns
    > for scanning.

    I guess for debugging pfns it would be also useful to print their values
    also in mm_compaction_end.

    > In combination with the direct reclaim and slab trace points
    > it should be possible to estimate most allocation-related overhead for
    > a workload.
    >
    > Signed-off-by: Mel Gorman <mgorman@suse.de>
    > ---
    > include/trace/events/compaction.h | 42 +++++++++++++++++++++++++++++++++++++++
    > mm/compaction.c | 4 ++++
    > 2 files changed, 46 insertions(+)
    >
    > diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h
    > index fde1b3e..f4e115a 100644
    > --- a/include/trace/events/compaction.h
    > +++ b/include/trace/events/compaction.h
    > @@ -67,6 +67,48 @@ TRACE_EVENT(mm_compaction_migratepages,
    > __entry->nr_failed)
    > );
    >
    > +TRACE_EVENT(mm_compaction_begin,
    > + TP_PROTO(unsigned long zone_start, unsigned long migrate_start,
    > + unsigned long zone_end, unsigned long free_start),
    > +
    > + TP_ARGS(zone_start, migrate_start, zone_end, free_start),

    IMHO a better order would be:
    zone_start, migrate_start, free_start, zone_end
    (well especially in the TP_printk part anyway).

    > +
    > + TP_STRUCT__entry(
    > + __field(unsigned long, zone_start)
    > + __field(unsigned long, migrate_start)
    > + __field(unsigned long, zone_end)
    > + __field(unsigned long, free_start)
    > + ),
    > +
    > + TP_fast_assign(
    > + __entry->zone_start = zone_start;
    > + __entry->migrate_start = migrate_start;
    > + __entry->zone_end = zone_end;
    > + __entry->free_start = free_start;
    > + ),
    > +
    > + TP_printk("zone_start=%lu migrate_start=%lu zone_end=%lu free_start=%lu",
    > + __entry->zone_start,
    > + __entry->migrate_start,
    > + __entry->zone_end,
    > + __entry->free_start)
    > +);
    > +
    > +TRACE_EVENT(mm_compaction_end,
    > + TP_PROTO(int status),
    > +
    > + TP_ARGS(status),
    > +
    > + TP_STRUCT__entry(
    > + __field(int, status)
    > + ),
    > +
    > + TP_fast_assign(
    > + __entry->status = status;
    > + ),
    > +
    > + TP_printk("status=%d", __entry->status)
    > +);
    >
    > #endif /* _TRACE_COMPACTION_H */
    >
    > diff --git a/mm/compaction.c b/mm/compaction.c
    > index c437893..78ff866 100644
    > --- a/mm/compaction.c
    > +++ b/mm/compaction.c
    > @@ -960,6 +960,8 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
    > if (compaction_restarting(zone, cc->order) && !current_is_kswapd())
    > __reset_isolation_suitable(zone);
    >
    > + trace_mm_compaction_begin(start_pfn, cc->migrate_pfn, end_pfn, cc->free_pfn);
    > +
    > migrate_prep_local();
    >
    > while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
    > @@ -1005,6 +1007,8 @@ out:
    > cc->nr_freepages -= release_freepages(&cc->freepages);
    > VM_BUG_ON(cc->nr_freepages != 0);
    >
    > + trace_mm_compaction_end(ret);
    > +
    > return ret;
    > }
    >
    >



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