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

Vlastimil Babka
2015-01-12T15:53:57Z

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.

> + TP_ARGS(order, gfp_mask, mode, alloc_flags, classzone_idx),
> +
> + TP_STRUCT__entry(
> + __field(int, order)
> + __field(gfp_t, gfp_mask)
> + __field(enum migrate_mode, mode)
> + __field(int, alloc_flags)
> + __field(int, classzone_idx)
> + ),
> +
> + TP_fast_assign(
> + __entry->order = order;
> + __entry->gfp_mask = gfp_mask;
> + __entry->mode = mode;
> + __entry->alloc_flags = alloc_flags;
> + __entry->classzone_idx = classzone_idx;
> + ),
> +
> + TP_printk("order=%d gfp_mask=0x%x mode=%d alloc_flags=0x%x classzone_idx=%d",
> + __entry->order,
> + __entry->gfp_mask,
> + (int)__entry->mode,
> + __entry->alloc_flags,
> + __entry->classzone_idx)
> +);
> +
> +DECLARE_EVENT_CLASS(mm_compaction_suitable_template,
> +
> + TP_PROTO(struct zone *zone,
> + int order,
> + int alloc_flags,
> + int classzone_idx,
> + int ret),
> +
> + TP_ARGS(zone, order, alloc_flags, classzone_idx, ret),
> +
> + TP_STRUCT__entry(
> + __field(int, nid)
> + __field(char *, name)
> + __field(int, order)
> + __field(int, alloc_flags)
> + __field(int, classzone_idx)
> + __field(int, ret)
> + ),
> +
> + TP_fast_assign(
> + __entry->nid = zone_to_nid(zone);
> + __entry->name = (char *)zone->name;
> + __entry->order = order;
> + __entry->alloc_flags = alloc_flags;
> + __entry->classzone_idx = classzone_idx;
> + __entry->ret = ret;
> + ),
> +
> + TP_printk("node=%d zone=%-8s order=%d alloc_flags=0x%x classzone_idx=%d ret=%s",
> + __entry->nid,
> + __entry->name,
> + __entry->order,
> + __entry->alloc_flags,
> + __entry->classzone_idx,
> + compaction_status_string[__entry->ret])
> +);
> +
> +DEFINE_EVENT(mm_compaction_suitable_template, mm_compaction_finished,
> +
> + TP_PROTO(struct zone *zone,
> + int order,
> + int alloc_flags,
> + int classzone_idx,
> + int ret),
> +
> + TP_ARGS(zone, order, alloc_flags, classzone_idx, ret)
> +);
> +
> +DEFINE_EVENT(mm_compaction_suitable_template, mm_compaction_suitable,
> +
> + TP_PROTO(struct zone *zone,
> + int order,
> + int alloc_flags,
> + int classzone_idx,
> + int ret),
> +
> + TP_ARGS(zone, order, alloc_flags, classzone_idx, ret)
> +);
> +
> #endif /* _TRACE_COMPACTION_H */
>
> /* This part must be outside protection */
> diff --git a/mm/compaction.c b/mm/compaction.c
> index be28469..7500f01 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -25,6 +25,8 @@ char *compaction_status_string[] = {
> "continue",
> "partial",
> "complete",
> + "no_suitable_page",
> + "not_suitable_zone",
> };
>
> static inline void count_compact_event(enum vm_event_item item)
> @@ -1048,7 +1050,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
> return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
> }
>
> -static int compact_finished(struct zone *zone, struct compact_control *cc,
> +static int __compact_finished(struct zone *zone, struct compact_control *cc,
> const int migratetype)
> {
> unsigned int order;
> @@ -1103,7 +1105,21 @@ static int compact_finished(struct zone *zone, struct compact_control *cc,
> return COMPACT_PARTIAL;
> }
>
> - return COMPACT_CONTINUE;
> + return COMPACT_NO_SUITABLE_PAGE;
> +}
> +
> +static int compact_finished(struct zone *zone, struct compact_control *cc,
> + const int migratetype)
> +{
> + int ret;
> +
> + ret = __compact_finished(zone, cc, migratetype);
> + trace_mm_compaction_finished(zone, cc->order, cc->alloc_flags,
> + cc->classzone_idx, ret);
> + if (ret == COMPACT_NO_SUITABLE_PAGE)
> + ret = COMPACT_CONTINUE;
> +
> + return ret;
> }
>
> /*
> @@ -1113,7 +1129,7 @@ static int compact_finished(struct zone *zone, struct compact_control *cc,
> * COMPACT_PARTIAL - If the allocation would succeed without compaction
> * COMPACT_CONTINUE - If compaction should run now
> */
> -unsigned long compaction_suitable(struct zone *zone, int order,
> +static unsigned long __compaction_suitable(struct zone *zone, int order,
> int alloc_flags, int classzone_idx)
> {
> int fragindex;
> @@ -1157,11 +1173,25 @@ unsigned long compaction_suitable(struct zone *zone, int order,
> */
> fragindex = fragmentation_index(zone, order);
> if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
> - return COMPACT_SKIPPED;
> + return COMPACT_NOT_SUITABLE_ZONE;
>
> return COMPACT_CONTINUE;
> }
>
> +unsigned long compaction_suitable(struct zone *zone, int order,
> + int alloc_flags, int classzone_idx)
> +{
> + unsigned long ret;
> +
> + ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx);
> + trace_mm_compaction_suitable(zone, order, alloc_flags,
> + classzone_idx, ret);
> + if (ret == COMPACT_NOT_SUITABLE_ZONE)
> + ret = COMPACT_SKIPPED;
> +
> + return ret;
> +}
> +
> static int compact_zone(struct zone *zone, struct compact_control *cc)
> {
> int ret;
> @@ -1377,6 +1407,9 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist,
> if (!order || !may_enter_fs || !may_perform_io)
> return COMPACT_SKIPPED;
>
> + trace_mm_compaction_try_to_compact_pages(order, gfp_mask, mode,
> + alloc_flags, classzone_idx);
> +
> /* Compact each zone in the list */
> for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
> nodemask) {
>