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Subject[PATCH 1/6] tracing, page-allocator: Add trace events for page allocation and page freeing
Date
This patch adds trace events for the allocation and freeing of pages,
including the freeing of pagevecs. Using the events, it will be known what
struct page and pfns are being allocated and freed and what the call site
was in many cases.

The page alloc tracepoints be used as an indicator as to whether the workload
was heavily dependant on the page allocator or not. You can make a guess based
on vmstat but you can't get a per-process breakdown. Depending on the call
path, the call_site for page allocation may be __get_free_pages() instead
of a useful callsite. Instead of passing down a return address similar to
slab debugging, the user should enable the stacktrace and seg-addr options
to get a proper stack trace.

The pagevec free tracepoint has a different usecase. It can be used to get
a idea of how many pages are being dumped off the LRU and whether it is
kswapd doing the work or a process doing direct reclaim.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Rik van Riel <riel@redhat.com>
---
include/trace/events/kmem.h | 77 +++++++++++++++++++++++++++++++++++++++++++
mm/page_alloc.c | 7 +++-
2 files changed, 83 insertions(+), 1 deletions(-)
diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index 1493c54..8ab0f98 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -225,6 +225,83 @@ TRACE_EVENT(kmem_cache_free,

TP_printk("call_site=%lx ptr=%p", __entry->call_site, __entry->ptr)
);
+
+TRACE_EVENT(mm_page_free_direct,
+
+ TP_PROTO(struct page *page, unsigned int order),
+
+ TP_ARGS(page, order),
+
+ TP_STRUCT__entry(
+ __field( struct page *, page )
+ __field( unsigned int, order )
+ ),
+
+ TP_fast_assign(
+ __entry->page = page;
+ __entry->order = order;
+ ),
+
+ TP_printk("page=%p pfn=%lu order=%d",
+ __entry->page,
+ page_to_pfn(__entry->page),
+ __entry->order)
+);
+
+TRACE_EVENT(mm_pagevec_free,
+
+ TP_PROTO(struct page *page, int order, int cold),
+
+ TP_ARGS(page, order, cold),
+
+ TP_STRUCT__entry(
+ __field( struct page *, page )
+ __field( int, order )
+ __field( int, cold )
+ ),
+
+ TP_fast_assign(
+ __entry->page = page;
+ __entry->order = order;
+ __entry->cold = cold;
+ ),
+
+ TP_printk("page=%p pfn=%lu order=%d cold=%d",
+ __entry->page,
+ page_to_pfn(__entry->page),
+ __entry->order,
+ __entry->cold)
+);
+
+TRACE_EVENT(mm_page_alloc,
+
+ TP_PROTO(struct page *page, unsigned int order,
+ gfp_t gfp_flags, int migratetype),
+
+ TP_ARGS(page, order, gfp_flags, migratetype),
+
+ TP_STRUCT__entry(
+ __field( struct page *, page )
+ __field( unsigned int, order )
+ __field( gfp_t, gfp_flags )
+ __field( int, migratetype )
+ ),
+
+ TP_fast_assign(
+ __entry->page = page;
+ __entry->order = order;
+ __entry->gfp_flags = gfp_flags;
+ __entry->migratetype = migratetype;
+ ),
+
+ TP_printk("page=%p pfn=%lu order=%d migratetype=%d gfp_flags=%s",
+ __entry->page,
+ page_to_pfn(__entry->page),
+ __entry->order,
+ __entry->migratetype,
+ show_gfp_flags(__entry->gfp_flags))
+);
+
#endif /* _TRACE_KMEM_H */

/* This part must be outside protection */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d052abb..f3f6039 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1062,6 +1062,7 @@ static void free_hot_cold_page(struct page *page, int cold)

void free_hot_page(struct page *page)
{
+ trace_mm_page_free_direct(page, 0);
free_hot_cold_page(page, 0);
}

@@ -1905,6 +1906,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
zonelist, high_zoneidx, nodemask,
preferred_zone, migratetype);

+ trace_mm_page_alloc(page, order, gfp_mask, migratetype);
return page;
}
EXPORT_SYMBOL(__alloc_pages_nodemask);
@@ -1945,13 +1947,16 @@ void __pagevec_free(struct pagevec *pvec)
{
int i = pagevec_count(pvec);

- while (--i >= 0)
+ while (--i >= 0) {
+ trace_mm_pagevec_free(pvec->pages[i], 0, pvec->cold);
free_hot_cold_page(pvec->pages[i], pvec->cold);
+ }
}

void __free_pages(struct page *page, unsigned int order)
{
if (put_page_testzero(page)) {
+ trace_mm_page_free_direct(page, order);
if (order == 0)
free_hot_page(page);
else
--
1.6.3.3


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