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Commit 81d68a96 authored by Steven Rostedt's avatar Steven Rostedt Committed by Thomas Gleixner
Browse files

ftrace: trace irq disabled critical timings 



This patch adds latency tracing for critical timings
(how long interrupts are disabled for).

 "irqsoff" is added to /debugfs/tracing/available_tracers

Note:
  tracing_max_latency
    also holds the max latency for irqsoff (in usecs).
   (default to large number so one must start latency tracing)

  tracing_thresh
    threshold (in usecs) to always print out if irqs off
    is detected to be longer than stated here.
    If irq_thresh is non-zero, then max_irq_latency
    is ignored.

Here's an example of a trace with ftrace_enabled = 0

=======
preemption latency trace v1.1.5 on 2.6.24-rc7
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
--------------------------------------------------------------------
 latency: 100 us, #3/3, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
    -----------------
 => started at: _spin_lock_irqsave+0x2a/0xb7
 => ended at:   _spin_unlock_irqrestore+0x32/0x5f

                 _------=> CPU#
                / _-----=> irqs-off
               | / _----=> need-resched
               || / _---=> hardirq/softirq
               ||| / _--=> preempt-depth
               |||| /
               |||||     delay
   cmd     pid ||||| time  |   caller
      \   /    |||||   \   |   /
 swapper-0     1d.s3    0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
 swapper-0     1d.s3  100us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1d.s3  100us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)

vim:ft=help
=======

And this is a trace with ftrace_enabled == 1

=======
preemption latency trace v1.1.5 on 2.6.24-rc7
--------------------------------------------------------------------
 latency: 102 us, #12/12, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
    -----------------
 => started at: _spin_lock_irqsave+0x2a/0xb7
 => ended at:   _spin_unlock_irqrestore+0x32/0x5f

                 _------=> CPU#
                / _-----=> irqs-off
               | / _----=> need-resched
               || / _---=> hardirq/softirq
               ||| / _--=> preempt-depth
               |||| /
               |||||     delay
   cmd     pid ||||| time  |   caller
      \   /    |||||   \   |   /
 swapper-0     1dNs3    0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
 swapper-0     1dNs3   46us : e1000_read_phy_reg+0x16/0x225 [e1000] (e1000_update_stats+0x5e2/0x64c [e1000])
 swapper-0     1dNs3   46us : e1000_swfw_sync_acquire+0x10/0x99 [e1000] (e1000_read_phy_reg+0x49/0x225 [e1000])
 swapper-0     1dNs3   46us : e1000_get_hw_eeprom_semaphore+0x12/0xa6 [e1000] (e1000_swfw_sync_acquire+0x36/0x99 [e1000])
 swapper-0     1dNs3   47us : __const_udelay+0x9/0x47 (e1000_read_phy_reg+0x116/0x225 [e1000])
 swapper-0     1dNs3   47us+: __delay+0x9/0x50 (__const_udelay+0x45/0x47)
 swapper-0     1dNs3   97us : preempt_schedule+0xc/0x84 (__delay+0x4e/0x50)
 swapper-0     1dNs3   98us : e1000_swfw_sync_release+0xc/0x55 [e1000] (e1000_read_phy_reg+0x211/0x225 [e1000])
 swapper-0     1dNs3   99us+: e1000_put_hw_eeprom_semaphore+0x9/0x35 [e1000] (e1000_swfw_sync_release+0x50/0x55 [e1000])
 swapper-0     1dNs3  101us : _spin_unlock_irqrestore+0xe/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1dNs3  102us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1dNs3  102us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)

vim:ft=help
=======

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 352ad25a

arch/x86/kernel/process_64.c

+3 −0
Original line number Diff line number Diff line
@@ -165,7 +165,10 @@ void cpu_idle(void) 
			 */

			local_irq_disable();

			enter_idle();

			/* Don't trace irqs off for idle */

			stop_critical_timings();

			idle();

			start_critical_timings();

			/* In many cases the interrupt that ended idle

			   has already called exit_idle. But some idle

			   loops can be woken up without interrupt. */

arch/x86/lib/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ 
obj-$(CONFIG_SMP) := msr-on-cpu.o



lib-y := delay_$(BITS).o

lib-y += thunk_$(BITS).o

lib-y += usercopy_$(BITS).o getuser_$(BITS).o putuser_$(BITS).o

lib-y += memcpy_$(BITS).o

arch/x86/lib/thunk_32.S

0 → 100644
+47 −0
Original line number Diff line number Diff line 
/*

 * Trampoline to trace irqs off. (otherwise CALLER_ADDR1 might crash)

 * Copyright 2008 by Steven Rostedt, Red Hat, Inc

 *  (inspired by Andi Kleen's thunk_64.S)

 * Subject to the GNU public license, v.2. No warranty of any kind.

 */



	#include <linux/linkage.h>



#define ARCH_TRACE_IRQS_ON			\

	pushl %eax;				\

	pushl %ecx;				\

	pushl %edx;				\

	call trace_hardirqs_on;			\

	popl %edx;				\

	popl %ecx;				\

	popl %eax;



#define ARCH_TRACE_IRQS_OFF			\

	pushl %eax;				\

	pushl %ecx;				\

	pushl %edx;				\

	call trace_hardirqs_off;		\

	popl %edx;				\

	popl %ecx;				\

	popl %eax;



#ifdef CONFIG_TRACE_IRQFLAGS

	/* put return address in eax (arg1) */

	.macro thunk_ra name,func

	.globl \name

\name:

	pushl %eax

	pushl %ecx

	pushl %edx

	/* Place EIP in the arg1 */

	movl 3*4(%esp), %eax

	call \func

	popl %edx

	popl %ecx

	popl %eax

	ret

	.endm



	thunk_ra trace_hardirqs_on_thunk,trace_hardirqs_on_caller

	thunk_ra trace_hardirqs_off_thunk,trace_hardirqs_off_caller

#endif

arch/x86/lib/thunk_64.S

+17 −2
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
 * Save registers before calling assembly functions. This avoids

 * disturbance of register allocation in some inline assembly constructs.

 * Copyright 2001,2002 by Andi Kleen, SuSE Labs.

 * Added trace_hardirqs callers - Copyright 2007 Steven Rostedt, Red Hat, Inc.

 * Subject to the GNU public license, v.2. No warranty of any kind.

 */
@@ -42,8 +43,22 @@ 
#endif	

	

#ifdef CONFIG_TRACE_IRQFLAGS

	thunk trace_hardirqs_on_thunk,trace_hardirqs_on

	thunk trace_hardirqs_off_thunk,trace_hardirqs_off

	/* put return address in rdi (arg1) */

	.macro thunk_ra name,func

	.globl \name

\name:

	CFI_STARTPROC

	SAVE_ARGS

	/* SAVE_ARGS pushs 9 elements */

	/* the next element would be the rip */

	movq 9*8(%rsp), %rdi

	call \func

	jmp  restore

	CFI_ENDPROC

	.endm



	thunk_ra trace_hardirqs_on_thunk,trace_hardirqs_on_caller

	thunk_ra trace_hardirqs_off_thunk,trace_hardirqs_off_caller

#endif



#ifdef CONFIG_DEBUG_LOCK_ALLOC

include/asm-x86/irqflags.h

+2 −22
Original line number Diff line number Diff line
@@ -179,8 +179,6 @@ static inline void trace_hardirqs_fixup(void) 
 * have a reliable stack. x86_64 only.

 */

#define SWAPGS_UNSAFE_STACK	swapgs

#define ARCH_TRACE_IRQS_ON		call trace_hardirqs_on_thunk

#define ARCH_TRACE_IRQS_OFF		call trace_hardirqs_off_thunk

#define ARCH_LOCKDEP_SYS_EXIT		call lockdep_sys_exit_thunk

#define ARCH_LOCKDEP_SYS_EXIT_IRQ	\

	TRACE_IRQS_ON; \
@@ -192,24 +190,6 @@ static inline void trace_hardirqs_fixup(void) 
	TRACE_IRQS_OFF;



#else

#define ARCH_TRACE_IRQS_ON			\

	pushl %eax;				\

	pushl %ecx;				\

	pushl %edx;				\

	call trace_hardirqs_on;			\

	popl %edx;				\

	popl %ecx;				\

	popl %eax;



#define ARCH_TRACE_IRQS_OFF			\

	pushl %eax;				\

	pushl %ecx;				\

	pushl %edx;				\

	call trace_hardirqs_off;		\

	popl %edx;				\

	popl %ecx;				\

	popl %eax;



#define ARCH_LOCKDEP_SYS_EXIT			\

	pushl %eax;				\

	pushl %ecx;				\
@@ -223,8 +203,8 @@ static inline void trace_hardirqs_fixup(void) 
#endif



#ifdef CONFIG_TRACE_IRQFLAGS

#  define TRACE_IRQS_ON		ARCH_TRACE_IRQS_ON

#  define TRACE_IRQS_OFF	ARCH_TRACE_IRQS_OFF

#  define TRACE_IRQS_ON		call trace_hardirqs_on_thunk;

#  define TRACE_IRQS_OFF	call trace_hardirqs_off_thunk;

#else

#  define TRACE_IRQS_ON

#  define TRACE_IRQS_OFF