Re: [PATCH V2 1/2] trace,x86: Add external_interrupts to the irq_vectors class
On 4/5/19 11:15 PM, Thomas Gleixner wrote: > On Mon, 1 Apr 2019, Daniel Bristot de Oliveira wrote: > >> Currently, the irq_vectors is showing the entry and exit events for >> the interrupts of the architecture, but not for external interrupts. > > Those are covered by the irq tracepoints. Is there a really good reason why > we need both? The irq_handler_* tracepoints might give the "imprecise" idea that more than one interrupts were raised when we have shared handlers. For instance: %< f-892 [000] d.h. 790.617251: external_interrupt_entry: vector=37 f-892 [000] d.h. 790.617257: irq_handler_entry: irq=11 name=uhci_hcd:usb3 f-892 [000] d.h. 790.617343: irq_handler_exit: irq=11 ret=handled f-892 [000] d.h. 790.617343: irq_handler_entry: irq=11 name=uhci_hcd:usb4 f-892 [000] d.h. 790.617349: irq_handler_exit: irq=11 ret=unhandled f-892 [000] d.h. 790.617350: irq_handler_entry: irq=11 name=qxl f-892 [000] d.h. 790.617360: irq_handler_exit: irq=11 ret=handled f-892 [000] d.h. 790.617387: external_interrupt_exit: vector=37 >% In this case, a single interrupt occurrence (vector 37) caused two handlers to handle their interrupt. >From a latency analysis perspective, the external_interrupt_* tracepoints turn clearer that a single interrupt interfered in the thread execution happened, not two separated executions of the same vector. The outer-most tracepoints also help to have a more precise accounting of the interference: Using the sum of the irq_handler_* tracepoints we have: (790.617343−790.617257)+(790.617349−790.617343)+(790.617360−790.617350) = 102 us While using the irq_vector based one: 790.617387-790.617251 = 136 us So, the proposed tracepoints help clarify the logical sequence of the interrupt handling, while increasing the precision of the measurements. Thoughts? -- Daniel > Thanks, > > tglx >
Re: [PATCH V2 1/2] trace,x86: Add external_interrupts to the irq_vectors class
On Mon, 1 Apr 2019, Daniel Bristot de Oliveira wrote: > Currently, the irq_vectors is showing the entry and exit events for > the interrupts of the architecture, but not for external interrupts. Those are covered by the irq tracepoints. Is there a really good reason why we need both? Thanks, tglx
[PATCH V2 1/2] trace,x86: Add external_interrupts to the irq_vectors class
Currently, the irq_vectors is showing the entry and exit events for
the interrupts of the architecture, but not for external interrupts.
Adds the tracepoints for external interrupts.
Example of output:
-0 [000] d.h. 102.890935: external_interrupt_entry: vector=35
-0 [000] d.h. 102.890960: external_interrupt_exit: vector=35
Changes from V1:
- Fix a compilation problem when CONFIG_X86_LOCAL_APIC is not set (kbuild
test)
Signed-off-by: Daniel Bristot de Oliveira
Cc: Thomas Gleixner
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: Andy Lutomirski
Cc: Clark Williams
Cc: linux-kernel@vger.kernel.org
Cc: x...@kernel.org
---
arch/x86/include/asm/trace/irq_vectors.h | 10 +-
arch/x86/kernel/irq.c| 2 ++
2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/trace/irq_vectors.h
b/arch/x86/include/asm/trace/irq_vectors.h
index 33b9d0f0aafe..38e73d56db70 100644
--- a/arch/x86/include/asm/trace/irq_vectors.h
+++ b/arch/x86/include/asm/trace/irq_vectors.h
@@ -138,6 +138,12 @@ DEFINE_IRQ_VECTOR_EVENT(deferred_error_apic);
DEFINE_IRQ_VECTOR_EVENT(thermal_apic);
#endif
+/*
+ * external_interrupt - called when entering/exiting from regular device
+ * interrupt vector handler.
+ */
+DEFINE_IRQ_VECTOR_EVENT(external_interrupt);
+
TRACE_EVENT(vector_config,
TP_PROTO(unsigned int irq, unsigned int vector,
@@ -385,7 +391,9 @@ TRACE_EVENT(vector_free_moved,
__entry->is_managed)
);
-
+#else /* CONFIG_X86_LOCAL_APIC */
+#define trace_external_interrupt_entry(vector) do {} while(0)
+#define trace_external_interrupt_exit(vector) do {} while(0)
#endif /* CONFIG_X86_LOCAL_APIC */
#undef TRACE_INCLUDE_PATH
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 59b5f2ea7c2f..715afe3a4f24 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -237,6 +237,7 @@ __visible unsigned int __irq_entry do_IRQ(struct pt_regs
*regs)
unsigned vector = ~regs->orig_ax;
entering_irq();
+ trace_external_interrupt_entry(vector);
/* entering_irq() tells RCU that we're not quiescent. Check it. */
RCU_LOCKDEP_WARN(!rcu_is_watching(), "IRQ failed to wake up RCU");
@@ -255,6 +256,7 @@ __visible unsigned int __irq_entry do_IRQ(struct pt_regs
*regs)
}
}
+ trace_external_interrupt_exit(vector);
exiting_irq();
set_irq_regs(old_regs);
--
2.19.0
