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 >
