On 07/06/2022 17:08, Rob Clark wrote:
On Tue, Jun 7, 2022 at 9:02 AM Rob Clark <robdclark@xxxxxxxxx> wrote:
On Tue, Jun 7, 2022 at 1:56 AM Tvrtko Ursulin
<tvrtko.ursulin@xxxxxxxxxxxxxxx> wrote:
On 06/06/2022 20:54, Rob Clark wrote:
From: Rob Clark <robdclark@xxxxxxxxxxxx>
Similar to AMD commit
874442541133 ("drm/amdgpu: Add show_fdinfo() interface"), using the
infrastructure added in previous patches, we add basic client info
and GPU engine utilisation for msm.
Example output:
# cat /proc/`pgrep glmark2`/fdinfo/6
pos: 0
flags: 02400002
mnt_id: 21
ino: 162
drm-driver: msm
drm-client-id: 7
drm-engine-gpu: 1734371319 ns
drm-cycles-gpu: 1153645024
drm-maxfreq-gpu: 800000000 Hz
See also: https://patchwork.freedesktop.org/patch/468505/
Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
---
Documentation/gpu/drm-usage-stats.rst | 21 +++++++++++++++++++++
drivers/gpu/drm/msm/msm_drv.c | 19 ++++++++++++++++++-
drivers/gpu/drm/msm/msm_gpu.c | 21 +++++++++++++++++++--
drivers/gpu/drm/msm/msm_gpu.h | 19 +++++++++++++++++++
4 files changed, 77 insertions(+), 3 deletions(-)
diff --git a/Documentation/gpu/drm-usage-stats.rst b/Documentation/gpu/drm-usage-stats.rst
index 6c9f166a8d6f..60e5cc9c13ad 100644
--- a/Documentation/gpu/drm-usage-stats.rst
+++ b/Documentation/gpu/drm-usage-stats.rst
@@ -105,6 +105,27 @@ object belong to this client, in the respective memory region.
Default unit shall be bytes with optional unit specifiers of 'KiB' or 'MiB'
indicating kibi- or mebi-bytes.
+- drm-cycles-<str> <uint>
+
+Engine identifier string must be the same as the one specified in the
+drm-engine-<str> tag and shall contain the number of busy cycles for the given
+engine.
+
+Values are not required to be constantly monotonic if it makes the driver
+implementation easier, but are required to catch up with the previously reported
+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.
+
+- drm-maxfreq-<str> <uint> [Hz|MHz|KHz]
+
+Engine identifier string must be the same as the one specified in the
+drm-engine-<str> tag and shall contain the maxium frequence for the given
maximum frequency
+engine. Taken together with drm-cycles-<str>, this can be used to calculate
+percentage utilization of the engine, whereas drm-engine-<str> only refects
reflects
+time active without considering what frequency the engine is operating as a
+percentage of it's maximum frequency.
Cycles vs max freq sounds very useful. My reservations is that how come
the idea hasn't happened in the CPU world. Or maybe it has and I am
un-informed?
I do often pay attention to both where tasks get scheduled, and the
individual CPU freq when I'm profiling CPU side stuff (eg. in
perfetto)
I could also report "always-count" cycles, I think, which could be
used by gputop to derive freq. I'd have to think about that a bit,
since keeping the result monotinic(ish) might be a bit tricky (the hw
counter loses state across runtime suspend)
In any case, if going with this I think we need to clarify the text that
the value should reflect the current soft limit, where the driver
supports that, in case it has been set to lower than the maximum
frequency hardware can support. I am thinking about avoiding "my gpu
cannot hit 100%" support incidents in cases when user/admin lowered the
soft limit for some reason. Possibly does not apply to msm but can apply
to i915, if we decided to export the same data.
Yes, with pm-qos thermal or userspace could limit the max freq.. but
we also internally use a pm-qos constraint to reduce freq when the GPU
is idle, and I don't think there is a good way to differentiate
*which* constraint is which. I'll add something involving the word
"recommended" ;-)
Hmm, or on second thought, maybe it would be better to, for drivers
that can, just report the soft limit separately?
Yes. I realized later soft-limit does not work, anything reported here
has to be invariant otherwise userspace cannot make sense of the
accumulated cycles vs changing freq. Max freq, as long as it is truly
max, as you were proposing, works I think.
Regards,
Tvrtko
