From 54e6171895006a006a71fd70183fef1f0375882b Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 16 Mar 2011 19:04:35 -0400
Subject: lttng-instrumentation/lttng-instrumentation-memory

LTTng instrumentation - memory page faults

Instrument the page fault entry and exit. Useful to detect delays caused by page
faults and bad memory usage patterns.

Those tracepoints are used by LTTng.

About the performance impact of tracepoints (which is comparable to markers),
even without immediate values optimizations, tests done by Hideo Aoki on ia64
show no regression. His test case was using hackbench on a kernel where
scheduler instrumentation (about 5 events in code scheduler code) was added.
See the "Tracepoints" patch header for performance result detail.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Andi Kleen <andi-suse@firstfloor.org>
CC: linux-mm@kvack.org
CC: Dave Hansen <haveblue@us.ibm.com>
CC: Masami Hiramatsu <mhiramat@redhat.com>
CC: 'Peter Zijlstra' <peterz@infradead.org>
CC: "Frank Ch. Eigler" <fche@redhat.com>
CC: 'Ingo Molnar' <mingo@elte.hu>
CC: 'Hideo AOKI' <haoki@redhat.com>
CC: Takashi Nishiie <t-nishiie@np.css.fujitsu.com>
CC: 'Steven Rostedt' <rostedt@goodmis.org>
CC: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
---
 mm/memory.c | 6 ++++++
 1 file changed, 6 insertions(+)

(limited to 'mm')

diff --git a/mm/memory.c b/mm/memory.c
index 17751b386f7..dc955dad52a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -58,6 +58,7 @@
 #include <linux/elf.h>
 #include <linux/gfp.h>
 #include <trace/swap.h>
+#include <trace/fault.h>
 
 #include <asm/io.h>
 #include <asm/pgalloc.h>
@@ -69,6 +70,8 @@
 #include "internal.h"
 
 DEFINE_TRACE(swap_in);
+DEFINE_TRACE(page_fault_get_user_entry);
+DEFINE_TRACE(page_fault_get_user_exit);
 
 #ifndef CONFIG_NEED_MULTIPLE_NODES
 /* use the per-pgdat data instead for discontigmem - mbligh */
@@ -1519,6 +1522,8 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 				int ret;
 				unsigned int fault_flags = 0;
 
+				trace_page_fault_get_user_entry(mm,
+					vma, start, foll_flags & FOLL_WRITE);
 				if (foll_flags & FOLL_WRITE)
 					fault_flags |= FAULT_FLAG_WRITE;
 				if (nonblocking)
@@ -1526,6 +1531,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 
 				ret = handle_mm_fault(mm, vma, start,
 							fault_flags);
+				trace_page_fault_get_user_exit(ret);
 
 				if (ret & VM_FAULT_ERROR) {
 					if (ret & VM_FAULT_OOM)
-- 
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