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authorSeiji Aguchi <seiji.aguchi@hds.com>2013-06-20 11:46:53 -0400
committerH. Peter Anvin <hpa@linux.intel.com>2013-06-20 22:25:34 -0700
commitcf910e83ae23692fdeefc7e506e504c4c468d38a (patch)
tree6e99fecdfd579bd7046488fb3c79e837d46eea08 /arch/x86/kernel/smp.c
parent629f4f9d59a27d8e58aa612e886e6a9a63ea7aeb (diff)
downloadlinux-cf910e83ae23692fdeefc7e506e504c4c468d38a.tar.bz2
x86, trace: Add irq vector tracepoints
[Purpose of this patch] As Vaibhav explained in the thread below, tracepoints for irq vectors are useful. http://www.spinics.net/lists/mm-commits/msg85707.html <snip> The current interrupt traces from irq_handler_entry and irq_handler_exit provide when an interrupt is handled. They provide good data about when the system has switched to kernel space and how it affects the currently running processes. There are some IRQ vectors which trigger the system into kernel space, which are not handled in generic IRQ handlers. Tracing such events gives us the information about IRQ interaction with other system events. The trace also tells where the system is spending its time. We want to know which cores are handling interrupts and how they are affecting other processes in the system. Also, the trace provides information about when the cores are idle and which interrupts are changing that state. <snip> On the other hand, my usecase is tracing just local timer event and getting a value of instruction pointer. I suggested to add an argument local timer event to get instruction pointer before. But there is another way to get it with external module like systemtap. So, I don't need to add any argument to irq vector tracepoints now. [Patch Description] Vaibhav's patch shared a trace point ,irq_vector_entry/irq_vector_exit, in all events. But there is an above use case to trace specific irq_vector rather than tracing all events. In this case, we are concerned about overhead due to unwanted events. So, add following tracepoints instead of introducing irq_vector_entry/exit. so that we can enable them independently. - local_timer_vector - reschedule_vector - call_function_vector - call_function_single_vector - irq_work_entry_vector - error_apic_vector - thermal_apic_vector - threshold_apic_vector - spurious_apic_vector - x86_platform_ipi_vector Also, introduce a logic switching IDT at enabling/disabling time so that a time penalty makes a zero when tracepoints are disabled. Detailed explanations are as follows. - Create trace irq handlers with entering_irq()/exiting_irq(). - Create a new IDT, trace_idt_table, at boot time by adding a logic to _set_gate(). It is just a copy of original idt table. - Register the new handlers for tracpoints to the new IDT by introducing macros to alloc_intr_gate() called at registering time of irq_vector handlers. - Add checking, whether irq vector tracing is on/off, into load_current_idt(). This has to be done below debug checking for these reasons. - Switching to debug IDT may be kicked while tracing is enabled. - On the other hands, switching to trace IDT is kicked only when debugging is disabled. In addition, the new IDT is created only when CONFIG_TRACING is enabled to avoid being used for other purposes. Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com> Link: http://lkml.kernel.org/r/51C323ED.5050708@hds.com Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Cc: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'arch/x86/kernel/smp.c')
-rw-r--r--arch/x86/kernel/smp.c30
1 files changed, 30 insertions, 0 deletions
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index d85837574a79..f4fe0b8879e0 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -30,6 +30,7 @@
#include <asm/proto.h>
#include <asm/apic.h>
#include <asm/nmi.h>
+#include <asm/trace/irq_vectors.h>
/*
* Some notes on x86 processor bugs affecting SMP operation:
*
@@ -264,6 +265,17 @@ void smp_reschedule_interrupt(struct pt_regs *regs)
*/
}
+void smp_trace_reschedule_interrupt(struct pt_regs *regs)
+{
+ ack_APIC_irq();
+ trace_reschedule_entry(RESCHEDULE_VECTOR);
+ __smp_reschedule_interrupt();
+ trace_reschedule_exit(RESCHEDULE_VECTOR);
+ /*
+ * KVM uses this interrupt to force a cpu out of guest mode
+ */
+}
+
static inline void call_function_entering_irq(void)
{
ack_APIC_irq();
@@ -283,6 +295,15 @@ void smp_call_function_interrupt(struct pt_regs *regs)
exiting_irq();
}
+void smp_trace_call_function_interrupt(struct pt_regs *regs)
+{
+ call_function_entering_irq();
+ trace_call_function_entry(CALL_FUNCTION_VECTOR);
+ __smp_call_function_interrupt();
+ trace_call_function_exit(CALL_FUNCTION_VECTOR);
+ exiting_irq();
+}
+
static inline void __smp_call_function_single_interrupt(void)
{
generic_smp_call_function_single_interrupt();
@@ -296,6 +317,15 @@ void smp_call_function_single_interrupt(struct pt_regs *regs)
exiting_irq();
}
+void smp_trace_call_function_single_interrupt(struct pt_regs *regs)
+{
+ call_function_entering_irq();
+ trace_call_function_single_entry(CALL_FUNCTION_SINGLE_VECTOR);
+ __smp_call_function_single_interrupt();
+ trace_call_function_single_exit(CALL_FUNCTION_SINGLE_VECTOR);
+ exiting_irq();
+}
+
static int __init nonmi_ipi_setup(char *str)
{
smp_no_nmi_ipi = true;