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Message-ID: <5a92b93c-6c6c-059a-c07b-a8b0b4b2b364@linux.intel.com>
Date: Fri, 22 Sep 2023 15:02:30 +0100
From: Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>
Cc: maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
robdclark@...il.com, quic_abhinavk@...cinc.com,
dmitry.baryshkov@...aro.org, sean@...rly.run,
marijn.suijten@...ainline.org, robh@...nel.org,
steven.price@....com, linux-arm-msm@...r.kernel.org,
linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
healych@...zon.com,
Boris Brezillon <boris.brezillon@...labora.com>,
kernel@...labora.com, freedreno@...ts.freedesktop.org
Subject: Re: [PATCH v6 6/6] drm/drm-file: Show finer-grained BO sizes in
drm_show_memory_stats
On 22/09/2023 12:03, Adrián Larumbe wrote:
> On 21.09.2023 11:14, Tvrtko Ursulin wrote:
>>
>> On 20/09/2023 16:32, Tvrtko Ursulin wrote:
>>>
>>> On 20/09/2023 00:34, Adrián Larumbe wrote:
>>>> The current implementation will try to pick the highest available size
>>>> display unit as soon as the BO size exceeds that of the previous
>>>> multiplier. That can lead to loss of precision in contexts of low memory
>>>> usage.
>>>>
>>>> The new selection criteria try to preserve precision, whilst also
>>>> increasing the display unit selection threshold to render more accurate
>>>> values.
>>>>
>>>> Signed-off-by: Adrián Larumbe <adrian.larumbe@...labora.com>
>>>> Reviewed-by: Boris Brezillon <boris.brezillon@...labora.com>
>>>> Reviewed-by: Steven Price <steven.price@....com>
>>>> ---
>>>> drivers/gpu/drm/drm_file.c | 5 ++++-
>>>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
>>>> index 762965e3d503..34cfa128ffe5 100644
>>>> --- a/drivers/gpu/drm/drm_file.c
>>>> +++ b/drivers/gpu/drm/drm_file.c
>>>> @@ -872,6 +872,8 @@ void drm_send_event(struct drm_device *dev, struct
>>>> drm_pending_event *e)
>>>> }
>>>> EXPORT_SYMBOL(drm_send_event);
>>>> +#define UPPER_UNIT_THRESHOLD 100
>>>> +
>>>> static void print_size(struct drm_printer *p, const char *stat,
>>>> const char *region, u64 sz)
>>>> {
>>>> @@ -879,7 +881,8 @@ static void print_size(struct drm_printer *p,
>>>> const char *stat,
>>>> unsigned u;
>>>> for (u = 0; u < ARRAY_SIZE(units) - 1; u++) {
>>>> - if (sz < SZ_1K)
>>>> + if ((sz & (SZ_1K - 1)) &&
>>>
>>> IS_ALIGNED worth it at all?
>>>
>>>> + sz < UPPER_UNIT_THRESHOLD * SZ_1K)
>>>> break;
>>>
>>> Excuse me for a late comment (I was away). I did not get what what is
>>> special about a ~10% threshold? Sounds to me just going with the lower
>>> unit, when size is not aligned to the higher one, would be better than
>>> sometimes precision-sometimes-not.
>>
>> FWIW both current and the threshold option make testing the feature very
>> annoying.
>
> How so?
I have to build in the knowledge of implementation details of
print_size() into my IGT in order to use the right size BOs, so test is
able to verify stats move as expected. It just feels wrong.
>> So I'd really propose we simply use smaller unit when unaligned.
>
> Like I said in the previous reply, for drm files whose overall BO size sum is enormous
> but not a multiple of a MiB, this would render huge number representations in KiB.
> I don't find this particularly comfortable to read, and then this extra precision
> would mean nothing to nvtop or gputop, which would have to scale the size to their
> available screen dimensions when plotting them.
I don't think numbers in KiB are so huge.
And I don't think people will end up reading them manually a lot anyway,
since you have to hunt the pid, and fd, etc.. It is much more realistic
that some tool like gputop will be used.
And I don't think consistency of units across drivers or whatever
matters. Even better to keep userspace parser on their toes and make
then follow drm-usage-stats.rst and not any implementations, at some
point in time.
Regards,
Tvrtko
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