[PATCH v2] percpu: improve percpu_alloc_percpu event trace

[Vasily Averin]

Added call_site, bytes_alloc and gfp_flags fields to the output
of the percpu_alloc_percpu ftrace event:

mkdir-4393  [001]   169.334788: percpu_alloc_percpu:
 call_site=mem_cgroup_css_alloc+0xa6 reserved=0 is_atomic=0 size=2408 align=8
  base_addr=0xffffc7117fc00000 off=402176 ptr=0x3dc867a62300 bytes_alloc=14448
   gfp_flags=GFP_KERNEL_ACCOUNT

This is required to track memcg-accounted percpu allocations.

Signed-off-by: Vasily Averin <vvs@xxxxxxxxxx>
---
v2: added call_site, improved patch description
---
 include/trace/events/percpu.h | 23 +++++++++++++++++------
 mm/percpu-internal.h          |  8 ++++----
 mm/percpu.c                   |  5 +++--
 3 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/include/trace/events/percpu.h b/include/trace/events/percpu.h
index df112a64f6c9..e989cefc0def 100644
--- a/include/trace/events/percpu.h
+++ b/include/trace/events/percpu.h
@@ -6,15 +6,20 @@
 #define _TRACE_PERCPU_H
 
 #include <linux/tracepoint.h>
+#include <trace/events/mmflags.h>
 
 TRACE_EVENT(percpu_alloc_percpu,
 
-	TP_PROTO(bool reserved, bool is_atomic, size_t size,
-		 size_t align, void *base_addr, int off, void __percpu *ptr),
+	TP_PROTO(unsigned long call_site,
+		 bool reserved, bool is_atomic, size_t size,
+		 size_t align, void *base_addr, int off,
+		 void __percpu *ptr, size_t bytes_alloc, gfp_t gfp_flags),
 
-	TP_ARGS(reserved, is_atomic, size, align, base_addr, off, ptr),
+	TP_ARGS(call_site, reserved, is_atomic, size, align, base_addr, off,
+		ptr, bytes_alloc, gfp_flags),
 
 	TP_STRUCT__entry(
+		__field(	unsigned long,		call_site	)
 		__field(	bool,			reserved	)
 		__field(	bool,			is_atomic	)
 		__field(	size_t,			size		)
@@ -22,9 +27,11 @@ TRACE_EVENT(percpu_alloc_percpu,
 		__field(	void *,			base_addr	)
 		__field(	int,			off		)
 		__field(	void __percpu *,	ptr		)
+		__field(	size_t,			bytes_alloc	)
+		__field(	gfp_t,			gfp_flags	)
 	),
-
 	TP_fast_assign(
+		__entry->call_site	= call_site;
 		__entry->reserved	= reserved;
 		__entry->is_atomic	= is_atomic;
 		__entry->size		= size;
@@ -32,12 +39,16 @@ TRACE_EVENT(percpu_alloc_percpu,
 		__entry->base_addr	= base_addr;
 		__entry->off		= off;
 		__entry->ptr		= ptr;
+		__entry->bytes_alloc	= bytes_alloc;
+		__entry->gfp_flags	= gfp_flags;
 	),
 
-	TP_printk("reserved=%d is_atomic=%d size=%zu align=%zu base_addr=%p off=%d ptr=%p",
+	TP_printk("call_site=%pS reserved=%d is_atomic=%d size=%zu align=%zu base_addr=%p off=%d ptr=%p bytes_alloc=%zu gfp_flags=%s",
+		  (void *)__entry->call_site,
 		  __entry->reserved, __entry->is_atomic,
 		  __entry->size, __entry->align,
-		  __entry->base_addr, __entry->off, __entry->ptr)
+		  __entry->base_addr, __entry->off, __entry->ptr,
+		  __entry->bytes_alloc, show_gfp_flags(__entry->gfp_flags))
 );
 
 TRACE_EVENT(percpu_free_percpu,
diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h
index 411d1593ef23..70b1ea23f4d2 100644
--- a/mm/percpu-internal.h
+++ b/mm/percpu-internal.h
@@ -113,7 +113,6 @@ static inline int pcpu_chunk_map_bits(struct pcpu_chunk *chunk)
 	return pcpu_nr_pages_to_map_bits(chunk->nr_pages);
 }
 
-#ifdef CONFIG_MEMCG_KMEM
 /**
  * pcpu_obj_full_size - helper to calculate size of each accounted object
  * @size: size of area to allocate in bytes
@@ -123,13 +122,14 @@ static inline int pcpu_chunk_map_bits(struct pcpu_chunk *chunk)
  */
 static inline size_t pcpu_obj_full_size(size_t size)
 {
-	size_t extra_size;
+	size_t extra_size = 0;
 
-	extra_size = size / PCPU_MIN_ALLOC_SIZE * sizeof(struct obj_cgroup *);
+#ifdef CONFIG_MEMCG_KMEM
+	extra_size += size / PCPU_MIN_ALLOC_SIZE * sizeof(struct obj_cgroup *);
+#endif
 
 	return size * num_possible_cpus() + extra_size;
 }
-#endif /* CONFIG_MEMCG_KMEM */
 
 #ifdef CONFIG_PERCPU_STATS
 
diff --git a/mm/percpu.c b/mm/percpu.c
index ea28db283044..3633eeefaa0d 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1884,8 +1884,9 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
 	ptr = __addr_to_pcpu_ptr(chunk->base_addr + off);
 	kmemleak_alloc_percpu(ptr, size, gfp);
 
-	trace_percpu_alloc_percpu(reserved, is_atomic, size, align,
-			chunk->base_addr, off, ptr);
+	trace_percpu_alloc_percpu(_RET_IP_, reserved, is_atomic, size, align,
+				  chunk->base_addr, off, ptr,
+				  pcpu_obj_full_size(size), gfp);
 
 	pcpu_memcg_post_alloc_hook(objcg, chunk, off, size);
 
-- 
2.31.1