[lttng-dev] [RFC-Patch 2/2] x86:Instruments page fault trace event

[Francis Deslauriers]

Signed-off-by: Francis Deslauriers <fdeslaur at gmail.com>
Reviewed-by: Raphaël Beamonte <raphael.beamonte at gmail.com>
---
 arch/x86/mm/fault.c |    7 +++++++
 mm/memory.c         |    5 +++++
 2 files changed, 12 insertions(+)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 2b97525..6ceaaaa 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -20,6 +20,9 @@
 #include <asm/fixmap.h>			/* VSYSCALL_START		*/
 #include <asm/context_tracking.h>	/* exception_enter(), ...	*/
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/fault.h>		/* trace_page_fault_*(), ...	*/
+
 /*
  * Page fault error code bits:
  *
@@ -754,12 +757,14 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 
 		if (likely(show_unhandled_signals))
 			show_signal_msg(regs, error_code, address, tsk);
+		trace_page_fault_entry(regs, address, error_code & PF_WRITE);
 
 		tsk->thread.cr2		= address;
 		tsk->thread.error_code	= error_code;
 		tsk->thread.trap_nr	= X86_TRAP_PF;
 
 		force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);
+		trace_page_fault_exit(-1);
 
 		return;
 	}
@@ -1183,7 +1188,9 @@ good_area:
 	 * make sure we exit gracefully rather than endlessly redo
 	 * the fault:
 	 */
+	trace_page_fault_entry(regs, address, write);
 	fault = handle_mm_fault(mm, vma, address, flags);
+	trace_page_fault_exit(fault);
 
 	if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
 		if (mm_fault_error(regs, error_code, address, fault))
diff --git a/mm/memory.c b/mm/memory.c
index 494526a..49a8119 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -67,6 +67,8 @@
 #include <asm/tlbflush.h>
 #include <asm/pgtable.h>
 
+#include <trace/events/fault.h>
+
 #include "internal.h"
 
 #ifdef LAST_NID_NOT_IN_PAGE_FLAGS
@@ -1828,8 +1830,11 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 				if (foll_flags & FOLL_NOWAIT)
 					fault_flags |= (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT);
 
+				trace_page_fault_entry(0, start,
+						foll_flags & FOLL_WRITE);
 				ret = handle_mm_fault(mm, vma, start,
 							fault_flags);
+				trace_page_fault_exit(ret);
 
 				if (ret & VM_FAULT_ERROR) {
 					if (ret & VM_FAULT_OOM)
-- 
1.7.10.4