linux-kernel - Re: [PATCH] tracing/sched: add 'next_policy' to trace_sched

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20250822100442.79691ab2@gandalf.local.home>
Date: Fri, 22 Aug 2025 10:04:42 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Xiang Gao <gxxa03070307@...il.com>
Cc: mhiramat@...nel.org, mathieu.desnoyers@...icios.com, andrii@...nel.org,
 mingo@...nel.org, oleg@...hat.com, akpm@...ux-foundation.org,
 gmonaco@...hat.com, ricardo.neri-calderon@...ux.intel.com,
 libo.chen@...cle.com, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, gaoxiang17 <gaoxiang17@...omi.com>,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Juri
 Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [PATCH] tracing/sched: add 'next_policy' to trace_sched_switch


[ Adding scheduler maintainers ]

On Fri, 22 Aug 2025 10:02:09 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Fri, 22 Aug 2025 18:51:13 +0800
> Xiang Gao <gxxa03070307@...il.com> wrote:
> 
> > From: gaoxiang17 <gaoxiang17@...omi.com>
> > 
> > Sometimes, when analyzing some real-time process issues, it is necessary to know the sched policy.
> > 
> > Show up in the trace as:
> > 
> >       113.457176: sched_switch: prev_comm=kcompactd0 prev_pid=30 prev_prio=120 prev_state=S ==> next_comm=kworker/u4:1 next_pid=27 next_prio=120 next_policy=0
> >       113.457282: sched_switch: prev_comm=kworker/u4:1 prev_pid=27 prev_prio=120 prev_state=I ==> next_comm=swapper/0 next_pid=0 next_prio=120 next_policy=0
> >       113.461166: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=kworker/u4:1 next_pid=27 next_prio=120 next_policy=0
> > 
> > Signed-off-by: gaoxiang17 <gaoxiang17@...omi.com>
> > ---
> >  include/trace/events/sched.h | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
> > index 7b2645b50e78..b416b7bafee4 100644
> > --- a/include/trace/events/sched.h
> > +++ b/include/trace/events/sched.h
> > @@ -234,6 +234,7 @@ TRACE_EVENT(sched_switch,
> >  		__array(	char,	next_comm,	TASK_COMM_LEN	)
> >  		__field(	pid_t,	next_pid			)
> >  		__field(	int,	next_prio			)
> > +		__field(	unsigned int,	next_policy	)
> >  	),
> >  
> >  	TP_fast_assign(
> > @@ -244,10 +245,11 @@ TRACE_EVENT(sched_switch,
> >  		memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
> >  		__entry->next_pid	= next->pid;
> >  		__entry->next_prio	= next->prio;
> > +		__entry->next_policy	= next->policy;
> >  		/* XXX SCHED_DEADLINE */
> >  	),
> >  
> > -	TP_printk("prev_comm=%s prev_pid=%d prev_prio=%d prev_state=%s%s ==> next_comm=%s next_pid=%d next_prio=%d",
> > +	TP_printk("prev_comm=%s prev_pid=%d prev_prio=%d prev_state=%s%s ==> next_comm=%s next_pid=%d next_prio=%d next_policy=%u",
> >  		__entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
> >  
> >  		(__entry->prev_state & (TASK_REPORT_MAX - 1)) ?
> > @@ -263,7 +265,7 @@ TRACE_EVENT(sched_switch,
> >  		  "R",
> >  
> >  		__entry->prev_state & TASK_REPORT_MAX ? "+" : "",
> > -		__entry->next_comm, __entry->next_pid, __entry->next_prio)
> > +		__entry->next_comm, __entry->next_pid, __entry->next_prio, __entry->next_policy)
> 
> 
> I'm fine with this change, but I'm not sure how Peter feels about updating
> scheduler tracepoints. That said, why not show the policy name?

Oh, and trace events are owned by the subsystem maintainers not the tracing
maintainers. You need to Cc them.

-- Steve


> 
> 	TP_printk("prev_comm=%s prev_pid=%d prev_prio=%d prev_state=%s%s ==> next_comm=%s next_pid=%d next_prio=%d next_policy=%s",
> 	[..]
> 		__entry->next_comm, __entry->next_pid, __entry->next_prio,
> 		__print_symbolic(__entry->next_policy,
> 			{ SCHED_NORMAL,		"normal" },
> 			{ SCHED_FIFO,		"FIFO" },
> 			{ SCHED_RR,		"RR" },
> 			{ SCHED_BATCH,		"batch" },
> 			{ SCHED_IDLE,		"idle" },
> 			{ SCHED_DEADLINE,	"deadline" },
> 			{ SCHED_EXT,		"sched_ext"}))
> 
> -- Steve
> 
> 
> 
> 
> 
> 
> >  );
> >  
> >  /*
>