linux-kernel - Re: [PATCH] irq/tracing: Add IRQ name to irq_handler

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Message-ID: <lg46wfjskaq4pcgjjnn7dqymlvgtdbbzcz4obzfqwymjxh2m7s@dfl7ww4p3rtv>
Date: Fri, 31 Jan 2025 09:15:54 -0300
From: Wander Lairson Costa <wander@...hat.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, "Darrick J. Wong" <djwong@...nel.org>, 
	Thomas Hellström <thomas.hellstrom@...ux.intel.com>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Takashi Iwai <tiwai@...e.de>, "open list:TRACING" <linux-kernel@...r.kernel.org>, 
	"open list:TRACING" <linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH] irq/tracing: Add IRQ name to irq_handler_exit tracepoint

On Thu, Jan 30, 2025 at 02:07:46PM -0500, Steven Rostedt wrote:
> On Thu, 30 Jan 2025 15:14:38 -0300
> Wander Lairson Costa <wander@...hat.com> wrote:
> 
> > The irq_handler_entry tracepoint includes a "name" field, which allows
> > for easy identification and filtering of specific IRQs. However, the
> > irq_handler_exit tracepoint lacks this field, making it difficult to
> > pair corresponding entry and exit events for analysis.
> > 
> > Add the "name" field to irq_handler_exit to enable consistent tracking
> > and correlation of IRQ entry and exit events.
> 
> I'm not sure what you mean by this.
> 

What I meant was looking at the name is easier when you are analysing
several interrupts overlapping on different cores, in special if they
are shared...

> 
> # trace-cmd record -e irq_handl* sleep 5
> # trace-cmd report
> 
>           <idle>-0     [000] d.h1.  4690.628641: irq_handler_entry:    irq=55 name=virtio5-output.0
>           <idle>-0     [000] d.h1.  4690.628650: irq_handler_exit:     irq=55 ret=handled
>           <idle>-0     [007] d.H1.  4690.628895: irq_handler_entry:    irq=54 name=virtio5-input.0
>           <idle>-0     [007] d.H1.  4690.628900: irq_handler_exit:     irq=54 ret=handled
>           <idle>-0     [000] d.h1.  4690.802977: irq_handler_entry:    irq=41 name=virtio2-req.0
>           <idle>-0     [000] dNh1.  4690.803046: irq_handler_exit:     irq=41 ret=handled
>           <idle>-0     [000] d.h1.  4690.813958: irq_handler_entry:    irq=41 name=virtio2-req.0
>           <idle>-0     [000] dNh1.  4690.814008: irq_handler_exit:     irq=41 ret=handled
>           <idle>-0     [000] d.H1.  4690.814257: irq_handler_entry:    irq=41 name=virtio2-req.0
>           <idle>-0     [000] dNH1.  4690.814301: irq_handler_exit:     irq=41 ret=handled
>           <idle>-0     [000] d.H1.  4690.815374: irq_handler_entry:    irq=41 name=virtio2-req.0
> 
> # cat /proc/interrupts |grep -e 55 -e 54 -e 41
>  41:        462          0          0          0          0          0          0          0 PCI-MSIX-0000:04:00.0   1-edge      virtio2-req.0
>  54:          0          0          0          0          0          0          0       4539 PCI-MSIX-0000:07:00.0   1-edge      virtio5-input.0
>  55:       4544          0          0          0          0          0          0          0 PCI-MSIX-0000:07:00.0   2-edge      virtio5-output.0
> RES:       1293       1411       1357       1307       1343       1345       1330       1315   Rescheduling interrupts
> 
> We have the names right there. Heck, I could probably write a plugin for
> trace-cmd to record the interrupt names in the trace.dat file and print
> them out with the events. Any analysis tool could also record that.
> 
> That's better than wasting ring buffer space for every event.
> 

...But you have a point I was not considering before (ring buffer
space).

> -- Steve
>