linux-kernel - Re: [PATCH v1] rtla: Save trace when option `--trace` is specified

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Message-ID: <20250304121053.06b84874@gandalf.local.home>
Date: Tue, 4 Mar 2025 12:10:53 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Tomas Glozar <tglozar@...hat.com>
Cc: Costa Shulyupin <costa.shul@...hat.com>, John Kacur <jkacur@...hat.com>,
 "Luis Claudio R. Goncalves" <lgoncalv@...hat.com>, Eder Zulian
 <ezulian@...hat.com>, Dan Carpenter <dan.carpenter@...aro.org>,
 linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] rtla: Save trace when option `--trace` is specified

On Tue, 4 Mar 2025 09:16:11 +0100
Tomas Glozar <tglozar@...hat.com> wrote:

> út 4. 3. 2025 v 9:00 odesílatel Tomas Glozar <tglozar@...hat.com> napsal:
> >
> > So we need to stop tracing here, before we save the trace, if we want
> > to do that. Perhaps combining this with the cleanup patch [1] and
> > doing the stopping in save_trace_to_file would make sense?
> >  
> 
> Also, the patch will also save the trace if running with -a and the
> threshold was not violated, which is not what one usually wants, e.g.:
> 
> $ rtla osnoise top -c 0 -q -a 10000000 -d 5s
>                                          Operating System Noise
> 
> duration:   0 00:00:05 | time is in us
> CPU Period       Runtime        Noise  % CPU Aval   Max Noise   Max
> Single          HW          NMI          IRQ      Softirq       Threa
> d
>  0 #4           4000000        37712    99.05720       10998
> 555        7624            0         4011           34           2
> 4
>  Saving trace to osnoise_trace.txt
> 
> I believe it would be better to add a new option, something like
> --force-trace, that would be used to save the trace even if there is
> no threshold violation. -t/--trace and -a could then be used with the
> same semantics as before.

As long is this is what you expect to happen. I just wanted to point out
that recording the trace while it is active means it may never stop
recording. If that is OK, then I'm fine with the change.

-- Steve