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Subject[PATCH 3/3] tracing, page-allocator: Add trace event for page traffic related to the buddy lists
Date
The page allocation trace event reports that a page was successfully allocated
but it does not specify where it came from. When analysing performance,
it can be important to distinguish between pages coming from the per-cpu
allocator and pages coming from the buddy lists as the latter requires the
zone lock to the taken and more data structures to be examined.

This patch adds a trace event for __rmqueue reporting when a page is being
allocated from the buddy lists. It distinguishes between being called
to refill the per-cpu lists or whether it is a high-order allocation.
Similarly, this patch adds an event to catch when the PCP lists are being
drained a little and pages are going back to the buddy lists. These two
events can be used as an indicator of how often the zone lock is being taken.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
---
include/trace/events/kmem.h | 54 +++++++++++++++++++++++++++++++++++++++++++
mm/page_alloc.c | 2 +
2 files changed, 56 insertions(+), 0 deletions(-)
diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index 91a057c..fbc3779 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -283,6 +283,60 @@ TRACE_EVENT(__alloc_pages_nodemask,
show_gfp_flags(__entry->gfp_flags))
);

+TRACE_EVENT(__rmqueue,
+
+ TP_PROTO(const void *page, unsigned int order,
+ int migratetype, int percpu_refill),
+
+ TP_ARGS(page, order, migratetype, percpu_refill),
+
+ TP_STRUCT__entry(
+ __field( const void *, page )
+ __field( unsigned int, order )
+ __field( int, migratetype )
+ __field( int, percpu_refill )
+ ),
+
+ TP_fast_assign(
+ __entry->page = page;
+ __entry->order = order;
+ __entry->migratetype = migratetype;
+ __entry->percpu_refill = percpu_refill;
+ ),
+
+ TP_printk("page = %p pfn=%lu order=%u migratetype=%d percpu_refill=%d",
+ __entry->page,
+ page_to_pfn((struct page *)__entry->page),
+ __entry->order,
+ __entry->migratetype,
+ __entry->percpu_refill)
+);
+
+TRACE_EVENT(free_pages_bulk,
+
+ TP_PROTO(const void *page, int order, int migratetype),
+
+ TP_ARGS(page, order, migratetype),
+
+ TP_STRUCT__entry(
+ __field( const void *, page )
+ __field( int, order )
+ __field( int, migratetype )
+ ),
+
+ TP_fast_assign(
+ __entry->page = page;
+ __entry->order = order;
+ __entry->migratetype = migratetype;
+ ),
+
+ TP_printk("page=%p pfn=%lu order=%d migratetype=%d",
+ __entry->page,
+ page_to_pfn((struct page *)__entry->page),
+ __entry->order,
+ __entry->migratetype)
+);
+
TRACE_EVENT(__rmqueue_fallback,

TP_PROTO(const void *page,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3fc9f09..f96bf2c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -535,6 +535,7 @@ static void free_pages_bulk(struct zone *zone, int count,
page = list_entry(list->prev, struct page, lru);
/* have to delete it as __free_one_page list manipulates */
list_del(&page->lru);
+ trace_free_pages_bulk(page, order, page_private(page));
__free_one_page(page, zone, order, page_private(page));
}
spin_unlock(&zone->lock);
@@ -878,6 +879,7 @@ retry_reserve:
}
}

+ trace___rmqueue(page, order, migratetype, order == 0);
return page;
}

--
1.6.3.3


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