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From: Daniel Vetter <daniel@ffwll.ch>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>,
	Jonathan Corbet <corbet@lwn.net>, David Airlie <airlied@linux.ie>,
	Sean Paul <sean@poorly.run>,
	dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org,
	Sean Paul <seanpaul@chromium.org>,
	Daniel Vetter <daniel.vetter@ffwll.ch>
Subject: Re: [PATCH v4] drm/trace: Buffer DRM logs in a ringbuffer accessible via debugfs
Date: Wed, 22 Jan 2020 09:06:50 +0100	[thread overview]
Message-ID: <20200122080650.GM43062@phenom.ffwll.local> (raw)
In-Reply-To: <20200120135621.34346e38@gandalf.local.home>

On Mon, Jan 20, 2020 at 01:56:21PM -0500, Steven Rostedt wrote:
> On Thu, 16 Jan 2020 07:27:22 +0100
> Daniel Vetter <daniel@ffwll.ch> wrote:
> 
> > On Tue, Jan 14, 2020 at 12:21:43PM -0500, Sean Paul wrote:
> > > From: Sean Paul <seanpaul@chromium.org>
> > > 
> > > This patch uses a ring_buffer to keep a "flight recorder" (name credit Weston)
> > > of DRM logs for a specified set of debug categories. The user writes a
> > > bitmask of debug categories to the "trace_mask" node and can read log
> > > messages from the "trace" node.
> > > 
> > > These nodes currently exist in debugfs under the dri directory. I
> > > intended on exposing all of this through tracefs originally, but the
> > > tracefs entry points are not exposed, so there's no way to create
> > > tracefs files from drivers at the moment. I think it would be a
> > > worthwhile endeavour, but one requiring more time and conversation to
> > > ensure the drm traces fit somewhere sensible.  
> > 
> > Hm, since the idea is to ship this in production environments debugfs is
> > out. sysfs is also kinda the wrong thing, so maybe trying to get this
> > stuffed into tracefs is actually the way to go?
> >
> 
> Why not use normal tracepoints and the tracing infrastructure? You can
> add your own instance as rasdaemon does, which isn't affected by other
> tracing. There's code now to even create these instances and enable and
> disable events from within the kernel.
> 
>   https://lore.kernel.org/lkml/1574276919-11119-1-git-send-email-divya.indi@oracle.com/

Hm, without looking at the details this indeed seems like the thing we
want ... Sean?
-Daniel

> 
> As this is tracefs, you can mount it without even compiling in debugfs.
> 
> -- Steve

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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  reply	other threads:[~2020-01-22  8:06 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14 17:21 [PATCH v4] drm/trace: Buffer DRM logs in a ringbuffer accessible via debugfs Sean Paul
2020-01-14 17:30 ` Steven Rostedt
2020-01-15  9:25 ` Joonas Lahtinen
2020-01-15 10:14 ` Pekka Paalanen
2020-01-15 13:31   ` Sean Paul
2020-01-15 10:28 ` Jani Nikula
2020-01-15 13:34   ` Sean Paul
2020-01-15 10:36 ` Chris Wilson
2020-01-15 13:41   ` Sean Paul
2020-01-15 14:01     ` Chris Wilson
2020-01-15 14:21       ` Sean Paul
2020-01-15 17:38         ` Chris Wilson
2020-01-15 18:29           ` Sean Paul
2020-01-16  6:27 ` Daniel Vetter
2020-01-20 18:56   ` Steven Rostedt
2020-01-22  8:06     ` Daniel Vetter [this message]
2020-01-22 15:39       ` Sean Paul
2020-01-27  8:58         ` Daniel Vetter

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