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

[Dmitry Baryshkov]

On 12/04/2023 23:34, Rob Clark wrote:
> On Wed, Apr 12, 2023 at 1:19 PM Dmitry Baryshkov
> <dmitry.baryshkov@xxxxxxxxxx> wrote:
> > On Wed, 12 Apr 2023 at 23:09, Rob Clark <robdclark@xxxxxxxxx> wrote:
> > > On Wed, Apr 12, 2023 at 5:47 AM Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> wrote:
> > > > On Wed, Apr 12, 2023 at 10:11:32AM +0200, Daniel Vetter wrote:
> > > > > On Wed, Apr 12, 2023 at 01:36:52AM +0300, Dmitry Baryshkov wrote:
> > > > > > 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.
> > > > >
> > > > > Yeah this sounds like a decent idea to me too. It might also solve the fun
> > > > > of various pci devices having very non-standard freq controls in sysfs
> > > > > (looking at least at i915 here ...)
> > > >
> > > > I also like the idea of having some common infrastructure for the GPU freq.
> > > >
> > > > hwmon have a good infrastructure, but they are more focused on individual
> > > > monitoring devices and not very welcomed to embedded monitoring and control.
> > > > I still want to check the opportunity to see if at least some freq control
> > > > could be aligned there.
> > > >
> > > > Another thing that complicates that is that there are multiple frequency
> > > > domains and controls with multipliers in Intel GPU that are not very
> > > > standard or easy to integrate.
> > > >
> > > > On a quick glace this devfreq seems neat because it aligns with the cpufreq
> > > > and governors. But again it would be hard to align with the multiple domains
> > > > and controls. But it deserves a look.
> > > >
> > > > I will take a look to both fronts for Xe: hwmon and devfreq. Right now on
> > > > Xe we have a lot less controls than i915, but I can imagine soon there
> > > > will be requirements to make that to grow and I fear that we end up just
> > > > like i915. So I will take a look before that happens.
> > >
> > > So it looks like i915 (dgpu only) and nouveau already use hwmon.. so
> > > maybe this is a good way to expose temp.  Maybe we can wire up some
> > > sort of helper for drivers which use thermal_cooling_device (which can
> > > be composed of multiple sensors) to give back an aggregate temp for
> > > hwmon to report?
> >
> > The thermal_device already registers the hwmon, see below. The
> > question is about linking that hwmon to the drm. Strictly speaking, I
> > don't think that we can reexport it in a clean way.
> >
> > # grep gpu /sys/class/hwmon/hwmon*/name
> > /sys/class/hwmon/hwmon15/name:gpu_top_thermal
> > /sys/class/hwmon/hwmon24/name:gpu_bottom_thermal
>
> I can't get excited about userspace relying on naming conventions or
> other heuristics like this.  

As you can guess, me neither. We are not in 2.4 world anymore.

> Also, userspace's view of the world is
> very much that there is a "gpu card", not a collection of parts.
> (Windows seems to have the same view of the world.)  So we have the
> component framework to assemble the various parts together into the
> "device" that userspace expects to deal with.  We need to do something
> similar for exposing temp and freq.

I think we are lookin for something close to device links. We need to 
create a userspace-visible link from one device to another across device 
hierarchy. Current device_link API is tied to suspend/resume, but the 
overall idea seems to be close enough (in my opinion).

> > # ls /sys/class/hwmon/hwmon15/ -l
> > lrwxrwxrwx    1 root     root             0 Jan 26 08:14 device ->
> > ../../thermal_zone15
> > -r--r--r--    1 root     root          4096 Jan 26 08:14 name
> > drwxr-xr-x    2 root     root             0 Jan 26 08:15 power
> > lrwxrwxrwx    1 root     root             0 Jan 26 08:12 subsystem ->
> > ../../../../../class/hwmon
> > -r--r--r--    1 root     root          4096 Jan 26 08:14 temp1_input
> > -rw-r--r--    1 root     root          4096 Jan 26 08:12 uevent
> >
> > > Freq could possibly be added to hwmon (ie. seems like a reasonable
> > > attribute to add).  Devfreq might also be an option but on arm it
> > > isn't necessarily associated with the drm device, whereas we could
> > > associate the hwmon with the drm device to make it easier for
> > > userspace to find.
> >
> > Possibly we can register a virtual 'passive' devfreq being driven by
> > another active devfreq device.
>
> That's all fine and good, but it has the same problem that existing
> hwmon's associated with the cooling-device have..
>
> BR,
> -R
>
> > > BR,
> > > -R
> > >
> > > > > I guess it would minimally be a good idea if we could document this, or
> > > > > maybe have a reference implementation in nvtop or whatever the cool thing
> > > > > is rn.
> > > > > -Daniel
> > > > >
> > > > > > > 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
> > > > >
> > > > > --
> > > > > Daniel Vetter
> > > > > Software Engineer, Intel Corporation
> > > > > http://blog.ffwll.ch
> >
> >
> >
> > --
> > With best wishes
> > Dmitry

--
With best wishes
Dmitry