Re: [PATCH v2 2/2] mm: vmscan: add PIDs to vmscan tracepoints

[Steven Rostedt <rostedt@goodmis.org>]

On Mon, 29 Dec 2025 13:29:42 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> I just don't like wasting valuable ring buffer space for something that can
> be easily determined without it.
> 
> How about this. I just wrote up this patch, and it could be something you
> use. I tested it against the sched waking events, by adding:
> 
>  		__entry->target_cpu	= task_cpu(p);
>  	),
>  
> -	TP_printk("comm=%s pid=%d prio=%d target_cpu=%03d",
> +	TP_printk("comm=%s pid=%d prio=%d target_cpu=%03d %s",
>  		  __entry->comm, __entry->pid, __entry->prio,
> -		  __entry->target_cpu)
> +		  __entry->target_cpu,
> +		  __event_in_irq() ? "(in-irq)" : "")
>  );
>  
> Which produces:
> 
>           <idle>-0     [003] d.h4.    44.832126: sched_waking:         comm=in:imklog pid=619 prio=120 target_cpu=006 (in-irq)
>           <idle>-0     [003] d.s3.    44.832180: sched_waking:         comm=rcu_preempt pid=15 prio=120 target_cpu=001 (in-irq)
>        in:imklog-619   [006] d..2.    44.832393: sched_waking:         comm=rs:main Q:Reg pid=620 prio=120 target_cpu=003 
> 
> You can see it adds "(in-irq)" when the even is executed from IRQ context
> (soft or hard irq). But I also added __event_in_hardirq() and
> __event_in_softirq() if you wanted to distinguish them.
> 
> Now you don't need to update what goes into the ring buffer (and waste its
> space), but only update the output format that makes it obvious that the
> task was in interrupt context or not.
> 
> I also used trace-cmd to record the events, and it still parses properly
> with no updates to libtraceevent needed.
> 
> Would this work for you?

If this would work for you. Feel free to take the patch I posted and use that:

   https://lore.kernel.org/all/20251229163515.3d1b0bba@gandalf.local.home/

-- Steve