linux-kernel - Re: [Freedreno] [PATCH v2 0/2] drm: fdinfo memory stats

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Message-ID: <CAA8EJppnEwcHM++YUYZGrNXEha=-ZVAexBdkMVsU52PTOs4VnA@mail.gmail.com>
Date:   Tue, 11 Apr 2023 20:35:48 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Rob Clark <robdclark@...il.com>
Cc:     dri-devel@...ts.freedesktop.org,
        Rob Clark <robdclark@...omium.org>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org,
        Emil Velikov <emil.l.velikov@...il.com>,
        Christopher Healy <healych@...zon.com>,
        open list <linux-kernel@...r.kernel.org>,
        Sean Paul <sean@...rly.run>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        freedreno@...ts.freedesktop.org
Subject: Re: [Freedreno] [PATCH v2 0/2] drm: fdinfo memory stats

On Tue, 11 Apr 2023 at 20:13, Rob Clark <robdclark@...il.com> wrote:
>
> On Tue, Apr 11, 2023 at 9:53 AM Daniel Vetter <daniel@...ll.ch> wrote:
> >
> > On Tue, Apr 11, 2023 at 09:47:32AM -0700, Rob Clark wrote:
> > > On Mon, Apr 10, 2023 at 2:06 PM Rob Clark <robdclark@...il.com> wrote:
> > > >
> > > > From: Rob Clark <robdclark@...omium.org>
> > > >
> > > > Similar motivation to other similar recent attempt[1].  But with an
> > > > attempt to have some shared code for this.  As well as documentation.
> > > >
> > > > It is probably a bit UMA-centric, I guess devices with VRAM might want
> > > > some placement stats as well.  But this seems like a reasonable start.
> > > >
> > > > Basic gputop support: https://patchwork.freedesktop.org/series/116236/
> > > > And already nvtop support: https://github.com/Syllo/nvtop/pull/204
> > >
> > > On a related topic, I'm wondering if it would make sense to report
> > > some more global things (temp, freq, etc) via fdinfo?  Some of this,
> > > tools like nvtop could get by trawling sysfs or other driver specific
> > > ways.  But maybe it makes sense to have these sort of things reported
> > > in a standardized way (even though they aren't really per-drm_file)
> >
> > I think that's a bit much layering violation, we'd essentially have to
> > reinvent the hwmon sysfs uapi in fdinfo. Not really a business I want to
> > be in :-)
>
> I guess this is true for temp (where there are thermal zones with
> potentially multiple temp sensors.. but I'm still digging my way thru
> the thermal_cooling_device stuff)

It is slightly ugly. All thermal zones and cooling devices are virtual
devices (so, even no connection to the particular tsens device). One
can either enumerate them by checking
/sys/class/thermal/thermal_zoneN/type or enumerate them through
/sys/class/hwmon. For cooling devices again the only enumeration is
through /sys/class/thermal/cooling_deviceN/type.

Probably it should be possible to push cooling devices and thermal
zones under corresponding providers. However I do not know if there is
a good way to correlate cooling device (ideally a part of GPU) to the
thermal_zone (which in our case is provided by tsens / temp_alarm
rather than GPU itself).

>
> But what about freq?  I think, esp for cases where some "fw thing" is
> controlling the freq we end up needing to use gpu counters to measure
> the freq.

For the freq it is slightly easier: /sys/class/devfreq/*, devices are
registered under proper parent (IOW, GPU). So one can read
/sys/class/devfreq/3d00000.gpu/cur_freq or
/sys/bus/platform/devices/3d00000.gpu/devfreq/3d00000.gpu/cur_freq.

However because of the components usage, there is no link from
/sys/class/drm/card0
(/sys/devices/platform/soc@...e00000.display-subsystem/ae01000.display-controller/drm/card0)
to /sys/devices/platform/soc@...d00000.gpu, the GPU unit.

Getting all these items together in a platform-independent way would
be definitely an important but complex topic.

>
> > What might be needed is better glue to go from the fd or fdinfo to the
> > right hw device and then crawl around the hwmon in sysfs automatically. I
> > would not be surprised at all if we really suck on this, probably more
> > likely on SoC than pci gpus where at least everything should be under the
> > main pci sysfs device.
>
> yeah, I *think* userspace would have to look at /proc/device-tree to
> find the cooling device(s) associated with the gpu.. at least I don't
> see a straightforward way to figure it out just for sysfs
>
> BR,
> -R
>
> > -Daniel
> >
> > >
> > > BR,
> > > -R
> > >
> > >
> > > > [1] https://patchwork.freedesktop.org/series/112397/
> > > >
> > > > Rob Clark (2):
> > > >   drm: Add fdinfo memory stats
> > > >   drm/msm: Add memory stats to fdinfo
> > > >
> > > >  Documentation/gpu/drm-usage-stats.rst | 21 +++++++
> > > >  drivers/gpu/drm/drm_file.c            | 79 +++++++++++++++++++++++++++
> > > >  drivers/gpu/drm/msm/msm_drv.c         | 25 ++++++++-
> > > >  drivers/gpu/drm/msm/msm_gpu.c         |  2 -
> > > >  include/drm/drm_file.h                | 10 ++++
> > > >  5 files changed, 134 insertions(+), 3 deletions(-)
> > > >
> > > > --
> > > > 2.39.2
> > > >
> >
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch



-- 
With best wishes
Dmitry