Re: [RFC] drm/amdgpu: Convert to common fdinfo format

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

Hi,

On 10/05/2022 09:48, Christian König wrote:
> Hi Tvrtko,
>
> Am 10.05.22 um 10:23 schrieb Tvrtko Ursulin:
> > From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> >
> > Convert fdinfo format to one documented in drm-usage-stats.rst.
> >
> > Opens/TODO:
> >   * Does someone from AMD want to take over this patch?
> >      (I have no access to amdgpu hardware so won't be able to test
> >       any hypothetical gputop work.)
>
> I can give that a try as soon as it is completed.

And how to motivate someone on your side to pick up the amdgpu work? :)

> >   * What are the semantics of AMD engine utilisation reported in 
> > percents?
>
> To be honest I haven't understood why we are using percents here either, 
> that is not something the kernel should mess with.
>
> >      * Can it align with what i915 does (same what msm will do) or need
> >        to document the alternative in the specification document? Both
> >        option are workable with instantaneous percent only needing 
> > support
> >        to be added to vendor agnostic gputop.
>
> I would prefer to just change to the ns format i915 and msm will be 
> using, that makes much more sense from my experience.
>
> As far as I know we haven't released any publicly available userspace 
> using the existing AMD specific format. So that should still be possible.

If amdgpu could export accumulated time context spent on engines that 
would indeed be perfect. It would make the gputop I sketched out most 
probably just work, as it did for Rob on msm.

In which case, apart from the admgpu work, it would just be a matter of 
me tidying that tool a bit and re-sending out for review.

> >   * Can amdgpu expose drm-client-id? Without it gputop will not work.
>
> How is that determined on i915 ? Does struct drm_file has that somewhere?

It should correspond 1:1 with drm_file, since the purpose is to enable 
gputop distinguish between unique open file descriptors (aka clients).

In theory it could be just a hash value of a struct drm_file pointer but 
that could confuse userspace if the struct gets reused within a single 
userspace sampling period.

Because of that I track it in i915 separately since I wanted to have an 
incrementing cyclic property to it - so that when a fd is closed and new 
opened there is no practical chance they would have the same drm-client-id.

> > * drm-engine-capacity - does the concept translate etc.
>
> I don't think we are going to need that.

Okay, that one is optional for cases when there is more than one engine 
of a type/class shown under a single entry in fdinfo. So when gputop 
translates accumulated time into percentages it can do the right thing. 
Code can already handle it not being present and assume one.

Regards,

Tvrtko

> Regards,
> Christian.
>
> > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> > Cc: David M Nieto <David.Nieto@xxxxxxx>
> > Cc: Christian König <christian.koenig@xxxxxxx>
> > Cc: Daniel Vetter <daniel@xxxxxxxx>
> > Acked-by: Christian König <christian.koenig@xxxxxxx>
> > ---
> >   Documentation/gpu/amdgpu/usage-stats.rst   | 28 ++++++++++++++++++++++
> >   Documentation/gpu/drm-usage-stats.rst      |  7 +++++-
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_fdinfo.c | 18 ++++++++++----
> >   3 files changed, 47 insertions(+), 6 deletions(-)
> >   create mode 100644 Documentation/gpu/amdgpu/usage-stats.rst
> >
> > diff --git a/Documentation/gpu/amdgpu/usage-stats.rst 
> > b/Documentation/gpu/amdgpu/usage-stats.rst
> > new file mode 100644
> > index 000000000000..8be5009bd1a9
> > --- /dev/null
> > +++ b/Documentation/gpu/amdgpu/usage-stats.rst
> > @@ -0,0 +1,28 @@
> > +.. _amdgpu-usage-stats:
> > +
> > +============================================
> > +AMDGPU DRM client usage stats implementation
> > +============================================
> > +
> > +The amdgpu driver implements the DRM client usage stats specification as
> > +documented in :ref:`drm-client-usage-stats`.
> > +
> > +Example of the output showing the implemented key value pairs and 
> > entirety of
> > +the currenly possible format options:
> > +
> > +::
> > +
> > +      pos:    0
> > +      flags:  0100002
> > +      mnt_id: 21
> > +      drm-driver: amdgpu
> > +      drm-pdev:   0000:03:00.0
> > +      drm-memory-vram: 0 KiB
> > +      drm-memory-gtt: 0 KiB
> > +      drm-memory-cpu: 0 KiB
> > +      drm-engine-...: 0 %
> > +                 ...
> > +
> > +Possible `drm-memory-` key names are: `vram`, `gtt`, `cpu`.
> > +
> > +Possible `drm-engine-` key names are: ``.
> > diff --git a/Documentation/gpu/drm-usage-stats.rst 
> > b/Documentation/gpu/drm-usage-stats.rst
> > index 6c9f166a8d6f..2d0ff6f2cc74 100644
> > --- a/Documentation/gpu/drm-usage-stats.rst
> > +++ b/Documentation/gpu/drm-usage-stats.rst
> > @@ -69,7 +69,7 @@ scope of each device, in which case `drm-pdev` shall 
> > be present as well.
> >   Userspace should make sure to not double account any usage 
> > statistics by using
> >   the above described criteria in order to associate data to 
> > individual clients.
> > -- drm-engine-<str>: <uint> ns
> > +- drm-engine-<str>: <uint> [ns|%]
> >   GPUs usually contain multiple execution engines. Each shall be given 
> > a stable
> >   and unique name (str), with possible values documented in the driver 
> > specific
> > @@ -84,6 +84,9 @@ larger value within a reasonable period. Upon 
> > observing a value lower than what
> >   was previously read, userspace is expected to stay with that larger 
> > previous
> >   value until a monotonic update is seen.
> > +Where time unit is given as a percentage...[AMD folks to fill the 
> > semantics
> > +and interpretation of that]...
> > +
> >   - drm-engine-capacity-<str>: <uint>
> >   Engine identifier string must be the same as the one specified in the
> > @@ -110,3 +113,5 @@ Driver specific implementations
> >   ===============================
> >   :ref:`i915-usage-stats`
> > +
> > +:ref:`amdgpu-usage-stats`
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fdinfo.c 
> > b/drivers/gpu/drm/amd/amdgpu/amdgpu_fdinfo.c
> > index 5a6857c44bb6..8cbae61f1b3b 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fdinfo.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fdinfo.c
> > @@ -32,6 +32,7 @@
> >   #include <drm/amdgpu_drm.h>
> >   #include <drm/drm_debugfs.h>
> > +#include <drm/drm_drv.h>
> >   #include "amdgpu.h"
> >   #include "amdgpu_vm.h"
> > @@ -83,11 +84,18 @@ void amdgpu_show_fdinfo(struct seq_file *m, struct 
> > file *f)
> >       amdgpu_bo_unreserve(root);
> >       amdgpu_bo_unref(&root);
> > -    seq_printf(m, "pdev:\t%04x:%02x:%02x.%d\npasid:\t%u\n", domain, bus,
> > +    /*
> > +     * 
> > ******************************************************************
> > +     * For text output format description please see 
> > drm-usage-stats.rst!
> > +     * 
> > ******************************************************************
> > +     */
> > +
> > +    seq_printf(m, "drm-driver:\t%s\n", file->minor->dev->driver->name);
> > +    seq_printf(m, "drm-pdev:\t%04x:%02x:%02x.%d\npasid:\t%u\n", 
> > domain, bus,
> >               dev, fn, fpriv->vm.pasid);
> > -    seq_printf(m, "vram mem:\t%llu kB\n", vram_mem/1024UL);
> > -    seq_printf(m, "gtt mem:\t%llu kB\n", gtt_mem/1024UL);
> > -    seq_printf(m, "cpu mem:\t%llu kB\n", cpu_mem/1024UL);
> > +    seq_printf(m, "drm-memory-vram:\t%llu KiB\n", vram_mem/1024UL);
> > +    seq_printf(m, "drm-memory-gtt:\t%llu KiB\n", gtt_mem/1024UL);
> > +    seq_printf(m, "drm-memory-cpu:\t%llu KiB\n", cpu_mem/1024UL);
> >       for (i = 0; i < AMDGPU_HW_IP_NUM; i++) {
> >           uint32_t count = amdgpu_ctx_num_entities[i];
> >           int idx = 0;
> > @@ -103,7 +111,7 @@ void amdgpu_show_fdinfo(struct seq_file *m, struct 
> > file *f)
> >               perc = div64_u64(10000 * total, min);
> >               frac = perc % 100;
> > -            seq_printf(m, "%s%d:\t%d.%d%%\n",
> > +            seq_printf(m, "drm-engine-%s%d:\t%d.%d %%\n",
> >                       amdgpu_ip_name[i],
> >                       idx, perc/100, frac);
> >           }