[PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath

[Janani Ravichandran]

Add tracepoints to the slowpath code to gather some information.
The tracepoints can also be used to find out how much time was spent in
the slowpath.

Signed-off-by: Janani Ravichandran <janani.rvchn...@gmail.com>
---
 include/trace/events/kmem.h | 40 ++++++++++++++++++++++++++++++++++++++++
 mm/page_alloc.c             |  5 +++++
 2 files changed, 45 insertions(+)

diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index 6b2e154..c19ab9f 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -169,6 +169,46 @@ TRACE_EVENT(mm_page_free,
                        __entry->order)
 );
 
+TRACE_EVENT(mm_slowpath_begin,
+
+       TP_PROTO(gfp_t gfp_mask, int order),
+
+       TP_ARGS(gfp_mask, order),
+
+       TP_STRUCT__entry(
+               __field(gfp_t, gfp_mask)
+               __field(int, order)
+       ),
+
+       TP_fast_assign(
+               __entry->gfp_mask = gfp_mask;
+               __entry->order = order;
+       ),
+
+       TP_printk("gfp_mask:%s order=%d",
+               show_gfp_flags(__entry->gfp_mask),
+               __entry->order)
+);
+
+TRACE_EVENT(mm_slowpath_end,
+
+       TP_PROTO(struct page *page),
+
+       TP_ARGS(page),
+
+       TP_STRUCT__entry(
+               __field(unsigned long, pfn)
+       ),
+
+       TP_fast_assign(
+               __entry->pfn = page ? page_to_pfn(page) : -1UL;
+       ),
+
+       TP_printk("page=%p pfn=%lu",
+               __entry->pfn != -1UL ? pfn_to_page(__entry->pfn) : NULL,
+               __entry->pfn != -1UL ? __entry->pfn : 0)
+);
+
 TRACE_EVENT(mm_page_free_batched,
 
        TP_PROTO(struct page *page, int cold),
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8b3e134..be9c688 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3595,6 +3595,8 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
                                (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))
                gfp_mask &= ~__GFP_ATOMIC;
 
+       trace_mm_slowpath_begin(gfp_mask, order);
+
 retry:
        if (gfp_mask & __GFP_KSWAPD_RECLAIM)
                wake_all_kswapds(order, ac);
@@ -3769,6 +3771,9 @@ noretry:
 nopage:
        warn_alloc_failed(gfp_mask, order, NULL);
 got_pg:
+
+       trace_mm_slowpath_end(page);
+
        return page;
 }
 
-- 
2.7.0