Message-ID: <CAF6AEGsE3NOe9TkEzrk5rr-D2PoKaxF5Yn3W8wWew8um6r2EXw@mail.gmail.com>
Date:   Tue, 11 Apr 2023 11:28:53 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
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, Apr 11, 2023 at 10:36 AM Dmitry Baryshkov
<dmitry.baryshkov@...aro.org> wrote:
>
> 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.

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"

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

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