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Message-ID: <e7d4cd81-c0a5-446c-95d2-6142d660c15b@cs.wisc.edu>
Date: Mon, 14 Apr 2025 15:35:41 -0500
From: Junxuan Liao <ljx@...wisc.edu>
To: linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org,
x86@...nel.org
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>, Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
"Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH] x86/tracing: introduce enter/exit tracepoint pairs for page
faults
Rename page_fault_{user,kernel} to page_fault_{user,kernel}_enter, and
add the exit counterparts. This might be useful for measuring page fault
handling latencies.
The exit tracepoints use a separate static key.
Signed-off-by: Junxuan Liao <ljx@...wisc.edu>
Link: https://lore.kernel.org/9e2ac1e3-d07d-4f17-970e-6b7a5248a5bb@cs.wisc.edu
---
arch/x86/include/asm/trace/common.h | 18 ++++++++++----
arch/x86/include/asm/trace/exceptions.h | 32 ++++++++++++++++++++-----
arch/x86/kernel/tracepoint.c | 22 +++++++++++++----
arch/x86/mm/fault.c | 21 +++++++++++++---
4 files changed, 75 insertions(+), 18 deletions(-)
diff --git a/arch/x86/include/asm/trace/common.h b/arch/x86/include/asm/trace/common.h
index f0f9bcdb74d9..4b289be75173 100644
--- a/arch/x86/include/asm/trace/common.h
+++ b/arch/x86/include/asm/trace/common.h
@@ -2,11 +2,21 @@
#define _ASM_TRACE_COMMON_H
#ifdef CONFIG_TRACING
-DECLARE_STATIC_KEY_FALSE(trace_pagefault_key);
-#define trace_pagefault_enabled() \
- static_branch_unlikely(&trace_pagefault_key)
+DECLARE_STATIC_KEY_FALSE(trace_pagefault_enter_key);
+DECLARE_STATIC_KEY_FALSE(trace_pagefault_exit_key);
+#define trace_pagefault_enter_enabled() \
+ static_branch_unlikely(&trace_pagefault_enter_key)
+#define trace_pagefault_exit_enabled() \
+ static_branch_unlikely(&trace_pagefault_exit_key)
#else
-static inline bool trace_pagefault_enabled(void) { return false; }
+static inline bool trace_pagefault_enter_enabled(void)
+{
+ return false;
+}
+static inline bool trace_pagefault_exit_enabled(void)
+{
+ return false;
+}
#endif
#endif
diff --git a/arch/x86/include/asm/trace/exceptions.h b/arch/x86/include/asm/trace/exceptions.h
index 6b1e87194809..76729fcdb249 100644
--- a/arch/x86/include/asm/trace/exceptions.h
+++ b/arch/x86/include/asm/trace/exceptions.h
@@ -8,8 +8,10 @@
#include <linux/tracepoint.h>
#include <asm/trace/common.h>
-extern int trace_pagefault_reg(void);
-extern void trace_pagefault_unreg(void);
+extern int trace_pagefault_enter_reg(void);
+extern void trace_pagefault_enter_unreg(void);
+extern int trace_pagefault_exit_reg(void);
+extern void trace_pagefault_exit_unreg(void);
DECLARE_EVENT_CLASS(x86_exceptions,
@@ -34,15 +36,33 @@ DECLARE_EVENT_CLASS(x86_exceptions,
(void *)__entry->address, (void *)__entry->ip,
__entry->error_code) );
-#define DEFINE_PAGE_FAULT_EVENT(name) \
+#define DEFINE_PAGE_FAULT_EVENT(name, reg, unreg) \
DEFINE_EVENT_FN(x86_exceptions, name, \
TP_PROTO(unsigned long address, struct pt_regs *regs, \
unsigned long error_code), \
TP_ARGS(address, regs, error_code), \
- trace_pagefault_reg, trace_pagefault_unreg);
+ reg, unreg)
-DEFINE_PAGE_FAULT_EVENT(page_fault_user);
-DEFINE_PAGE_FAULT_EVENT(page_fault_kernel);
+DEFINE_PAGE_FAULT_EVENT(
+ page_fault_user_enter,
+ trace_pagefault_enter_reg,
+ trace_pagefault_enter_unreg
+);
+DEFINE_PAGE_FAULT_EVENT(
+ page_fault_user_exit,
+ trace_pagefault_exit_reg,
+ trace_pagefault_exit_unreg
+);
+DEFINE_PAGE_FAULT_EVENT(
+ page_fault_kernel_enter,
+ trace_pagefault_enter_reg,
+ trace_pagefault_enter_unreg
+);
+DEFINE_PAGE_FAULT_EVENT(
+ page_fault_kernel_exit,
+ trace_pagefault_exit_reg,
+ trace_pagefault_exit_unreg
+);
#undef TRACE_INCLUDE_PATH
#undef TRACE_INCLUDE_FILE
diff --git a/arch/x86/kernel/tracepoint.c b/arch/x86/kernel/tracepoint.c
index 03ae1caaa878..108285046226 100644
--- a/arch/x86/kernel/tracepoint.c
+++ b/arch/x86/kernel/tracepoint.c
@@ -7,15 +7,27 @@
#include <asm/trace/exceptions.h>
-DEFINE_STATIC_KEY_FALSE(trace_pagefault_key);
+DEFINE_STATIC_KEY_FALSE(trace_pagefault_enter_key);
+DEFINE_STATIC_KEY_FALSE(trace_pagefault_exit_key);
-int trace_pagefault_reg(void)
+int trace_pagefault_enter_reg(void)
{
- static_branch_inc(&trace_pagefault_key);
+ static_branch_inc(&trace_pagefault_enter_key);
return 0;
}
-void trace_pagefault_unreg(void)
+void trace_pagefault_enter_unreg(void)
{
- static_branch_dec(&trace_pagefault_key);
+ static_branch_dec(&trace_pagefault_enter_key);
+}
+
+int trace_pagefault_exit_reg(void)
+{
+ static_branch_inc(&trace_pagefault_exit_key);
+ return 0;
+}
+
+void trace_pagefault_exit_unreg(void)
+{
+ static_branch_dec(&trace_pagefault_exit_key);
}
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 296d294142c8..cd933edf1e19 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1455,13 +1455,26 @@ static __always_inline void
trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
unsigned long address)
{
- if (!trace_pagefault_enabled())
+ if (!trace_pagefault_enter_enabled())
return;
if (user_mode(regs))
- trace_page_fault_user(address, regs, error_code);
+ trace_page_fault_user_enter(address, regs, error_code);
else
- trace_page_fault_kernel(address, regs, error_code);
+ trace_page_fault_kernel_enter(address, regs, error_code);
+}
+
+static __always_inline void
+trace_page_fault_exits(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address)
+{
+ if (!trace_pagefault_exit_enabled())
+ return;
+
+ if (user_mode(regs))
+ trace_page_fault_user_exit(address, regs, error_code);
+ else
+ trace_page_fault_kernel_exit(address, regs, error_code);
}
static __always_inline void
@@ -1487,6 +1500,8 @@ handle_page_fault(struct pt_regs *regs, unsigned long error_code,
*/
local_irq_disable();
}
+
+ trace_page_fault_exits(regs, error_code, address);
}
DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
--
2.48.1
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