Re: [PATCH V2 1/7] trace/events: Add gup trace events

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On 12/2/2015 8:07 PM, Steven Rostedt wrote:
On Wed,  2 Dec 2015 14:53:27 -0800
Yang Shi <yang.shi@xxxxxxxxxx> wrote:

page-faults events record the invoke to handle_mm_fault, but the invoke
may come from do_page_fault or gup. In some use cases, the finer event count
mey be needed, so add trace events support for:

__get_user_pages
__get_user_pages_fast
fixup_user_fault

Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxx>
---
  include/trace/events/gup.h | 71 ++++++++++++++++++++++++++++++++++++++++++++++
  1 file changed, 71 insertions(+)
  create mode 100644 include/trace/events/gup.h

diff --git a/include/trace/events/gup.h b/include/trace/events/gup.h
new file mode 100644
index 0000000..03a4674
--- /dev/null
+++ b/include/trace/events/gup.h
@@ -0,0 +1,71 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM gup
+
+#if !defined(_TRACE_GUP_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_GUP_H
+
+#include <linux/types.h>
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(gup_fixup_user_fault,
+
+	TP_PROTO(struct task_struct *tsk, struct mm_struct *mm,
+			unsigned long address, unsigned int fault_flags),
+
+	TP_ARGS(tsk, mm, address, fault_flags),

Arges added and not used by TP_fast_assign(), this will slow down the
code while tracing is enabled, as they need to be added to the trace
function call.

+
+	TP_STRUCT__entry(
+		__field(	unsigned long,	address		)
+	),
+
+	TP_fast_assign(
+		__entry->address	= address;
+	),
+
+	TP_printk("address=%lx",  __entry->address)
+);
+
+TRACE_EVENT(gup_get_user_pages,
+
+	TP_PROTO(struct task_struct *tsk, struct mm_struct *mm,
+			unsigned long start, unsigned long nr_pages),
+
+	TP_ARGS(tsk, mm, start, nr_pages),

Here too but this is worse. See below.

+
+	TP_STRUCT__entry(
+		__field(	unsigned long,	start		)
+		__field(	unsigned long,	nr_pages	)
+	),
+
+	TP_fast_assign(
+		__entry->start		= start;
+		__entry->nr_pages	= nr_pages;
+	),
+
+	TP_printk("start=%lx nr_pages=%lu", __entry->start, __entry->nr_pages)
+);
+
+TRACE_EVENT(gup_get_user_pages_fast,
+
+	TP_PROTO(unsigned long start, int nr_pages, int write,
+			struct page **pages),
+
+	TP_ARGS(start, nr_pages, write, pages),

This and the above "gup_get_user_pages" have the same entry field,
assign and printk. They should be combined into a DECLARE_EVENT_CLASS()
and two DEFINE_EVENT()s. That will save on size as the
DECLARE_EVENT_CLASS() is the biggest part of each TRACE_EVENT().

Thanks for the suggestion, will fix them in V3.

Regards,
Yang


-- Steve


+
+	TP_STRUCT__entry(
+		__field(	unsigned long,	start		)
+		__field(	unsigned long,	nr_pages	)
+	),
+
+	TP_fast_assign(
+		__entry->start  	= start;
+		__entry->nr_pages	= nr_pages;
+	),
+
+	TP_printk("start=%lx nr_pages=%lu",  __entry->start, __entry->nr_pages)
+);
+
+#endif /* _TRACE_GUP_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>


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