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

[Dmitry Baryshkov]

On 11/04/2023 21:28, Rob Clark wrote:
> On Tue, Apr 11, 2023 at 10:36 AM Dmitry Baryshkov
> <dmitry.baryshkov@xxxxxxxxxx> wrote:
> > On Tue, 11 Apr 2023 at 20:13, Rob Clark <robdclark@xxxxxxxxx> wrote:
> > > On Tue, Apr 11, 2023 at 9:53 AM Daniel Vetter <daniel@xxxxxxxx> 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@xxxxxxxxx> wrote:
> > > > > > From: Rob Clark <robdclark@xxxxxxxxxxxx>
> > > > > >
> > > > > > 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@0/ae00000.display-subsystem/ae01000.display-controller/drm/card0)
> > to /sys/devices/platform/soc@0/3d00000.gpu, the GPU unit.
> >
> > Getting all these items together in a platform-independent way would
> > be definitely an important but complex topic.
>
> But I don't believe any of the pci gpu's use devfreq ;-)
>
> And also, you can't expect the CPU to actually know the freq when fw
> is the one controlling freq.  We can, currently, have a reasonable
> approximation from devfreq but that stops if IFPC is implemented.  And
> other GPUs have even less direct control.  So freq is a thing that I
> don't think we should try to get from "common frameworks"

I think it might be useful to add another passive devfreq governor type 
for external frequencies. This way we can use the same interface to 
export non-CPU-controlled frequencies.

> BR,
> -R
>
> > > > 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

--
With best wishes
Dmitry