Re: [PATCH v2 5/9] drm: Add fdinfo memory stats

Tvrtko Ursulin
2023-05-02T08:29:48Z

On 28/04/2023 15:45, Rob Clark wrote:
> On Fri, Apr 28, 2023 at 3:56 AM Tvrtko Ursulin
> <tvrtko.ursulin@linux.intel.com> wrote:
>>
>>
>> On 27/04/2023 18:53, Rob Clark wrote:
>>> From: Rob Clark <robdclark@chromium.org>
>>>
>>> Add support to dump GEM stats to fdinfo.
>>>
>>> v2: Fix typos, change size units to match docs, use div_u64
>>> v3: Do it in core
>>> v4: more kerneldoc
>>>
>>> Signed-off-by: Rob Clark <robdclark@chromium.org>
>>> Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
>>> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>>> ---
>>> Documentation/gpu/drm-usage-stats.rst | 54 +++++++++++----
>>> drivers/gpu/drm/drm_file.c | 99 ++++++++++++++++++++++++++-
>>> include/drm/drm_file.h | 19 +++++
>>> include/drm/drm_gem.h | 30 ++++++++
>>> 4 files changed, 189 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/Documentation/gpu/drm-usage-stats.rst b/Documentation/gpu/drm-usage-stats.rst
>>> index 552195fb1ea3..bfc14150452c 100644
>>> --- a/Documentation/gpu/drm-usage-stats.rst
>>> +++ b/Documentation/gpu/drm-usage-stats.rst
>>> @@ -52,6 +52,9 @@ String shall contain the name this driver registered as via the respective
>>> Optional fully standardised keys
>>> --------------------------------
>>>
>>> +Identification
>>> +^^^^^^^^^^^^^^
>>> +
>>> - drm-pdev: <aaaa:bb.cc.d>
>>>
>>> For PCI devices this should contain the PCI slot address of the device in
>>> @@ -69,6 +72,9 @@ 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.
>>>
>>> +Utilization
>>> +^^^^^^^^^^^
>>> +
>>> - drm-engine-<str>: <uint> ns
>>>
>>> GPUs usually contain multiple execution engines. Each shall be given a stable
>>> @@ -93,18 +99,6 @@ exported engine corresponds to a group of identical hardware engines.
>>> In the absence of this tag parser shall assume capacity of one. Zero capacity
>>> is not allowed.
>>>
>>> -- drm-memory-<str>: <uint> [KiB|MiB]
>>> -
>>> -Each possible memory type which can be used to store buffer objects by the
>>> -GPU in question shall be given a stable and unique name to be returned as the
>>> -string here.
>>> -
>>> -Value shall reflect the amount of storage currently consumed by the buffer
>>> -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
>>> @@ -126,6 +120,42 @@ percentage utilization of the engine, whereas drm-engine-<str> only reflects
>>> time active without considering what frequency the engine is operating as a
>>> percentage of it's maximum frequency.
>>>
>>> +Memory
>>> +^^^^^^
>>> +
>>> +- drm-memory-<region>: <uint> [KiB|MiB]
>>> +
>>> +Each possible memory type which can be used to store buffer objects by the
>>> +GPU in question shall be given a stable and unique name to be returned as the
>>> +string here. The name "memory" is reserved to refer to normal system memory.
>>
>> How is the name memory reserved, I mean when which part of the key?
>> Obviously amdgpu exposes drm-memory-vram so it can't mean system memory
>> there.
>>
>> [Comes back later]
>>
>> Ah I see.. you meant the _region_ name "memory" is reserved. Which
>> applies to the below keys, not the one above. Hmm.. So for multi-region
>> drivers you meant like:
>
> right, I thought "drm-memory-memory" sounded silly, and otherwise
> "memory" fit elsewhere as below, so "memory" seemed like a reasonable
> region name ;-)
>
>> drm-total-memory:
>> drm-total-vram:
>>
>> Etc. Okay I think that works. All prefixes "drm-$category" become
>> reserved ones effectively but I think that is okay.
>>
>>> +
>>> +Value shall reflect the amount of storage currently consumed by the buffer
>>> +object belong to this client, in the respective memory region.
>>
>> OMG it is all my fault for mentioning buffer objects here... :)
>>
>> Maybe just fix the plural while moving.
>>
>> Or maybe there is time to s/buffer objects/memory/ too? Why not I think.
>> It would leave things more future proof.
>>
>>> +
>>> +Default unit shall be bytes with optional unit specifiers of 'KiB' or 'MiB'
>>> +indicating kibi- or mebi-bytes.
>>> +
>>> +- drm-shared-<region>: <uint> [KiB|MiB]
>>> +
>>> +The total size of buffers that are shared with another file (ie. have more
>>> +than a single handle).
>>> +
>>> +- drm-private-<region>: <uint> [KiB|MiB]
>>> +
>>> +The total size of buffers that are not shared with another file.
>>
>> You went back to private + shared for a specific reason? I thought we
>> agreed total + shared can be less confusing.
>
> opps, yes, I forgot to update the rst
>
>>> +
>>> +- drm-resident-<region>: <uint> [KiB|MiB]
>>> +
>>> +The total size of buffers that are resident in system memory.
>>
>> "..resident in the specified memory region."?
>>
>>> +
>>> +- drm-purgeable-<region>: <uint> [KiB|MiB]
>>> +
>>> +The total size of buffers that are purgeable.
>>> +
>>> +- drm-active-<region>: <uint> [KiB|MiB]
>>> +
>>> +The total size of buffers that are active on one or more rings.
>>
>> Under utilisation we used 'engines' so introducing 'rings' at least
>> needs clarification, maybe a terminology chapter? Or just use engines
>> for consistency?
>
> using "engines" works for me
>
>>> +
>>> Implementation Details
>>> ======================
>>>
>>> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
>>> index 6d5bdd684ae2..9321eb0bf020 100644
>>> --- a/drivers/gpu/drm/drm_file.c
>>> +++ b/drivers/gpu/drm/drm_file.c
>>> @@ -42,6 +42,7 @@
>>> #include <drm/drm_client.h>
>>> #include <drm/drm_drv.h>
>>> #include <drm/drm_file.h>
>>> +#include <drm/drm_gem.h>
>>> #include <drm/drm_print.h>
>>>
>>> #include "drm_crtc_internal.h"
>>> @@ -871,9 +872,105 @@ void drm_send_event(struct drm_device *dev, struct drm_pending_event *e)
>>> }
>>> EXPORT_SYMBOL(drm_send_event);
>>>
>>> +static void print_size(struct drm_printer *p, const char *stat,
>>> + const char *region, size_t sz)
>>> +{
>>> + const char *units[] = {"", " KiB", " MiB"};
>>> + unsigned u;
>>> +
>>> + for (u = 0; u < ARRAY_SIZE(units) - 1; u++) {
>>> + if (sz < SZ_1K)
>>> + break;
>>> + sz = div_u64(sz, SZ_1K);
>>> + }
>>> +
>>> + drm_printf(p, "drm-%s-%s:\t%zu%s\n", stat, region, sz, units[u]);
>>> +}
>>> +
>>> +/**
>>> + * drm_print_memory_stats - A helper to print memory stats
>>> + * @p: The printer to print output to
>>> + * @stats: The collected memory stats
>>> + * @supported_status: Bitmask of optional stats which are available
>>> + * @region: The memory region
>>> + *
>>> + */
>>> +void drm_print_memory_stats(struct drm_printer *p,
>>> + const struct drm_memory_stats *stats,
>>> + enum drm_gem_object_status supported_status,
>>> + const char *region)
>>> +{
>>> + print_size(p, "total", region, stats->private + stats->shared);
>>> + print_size(p, "shared", region, stats->shared);
>>
>> Ah just rst is out of date.
>>
>>> + print_size(p, "active", region, stats->active);
>>> +
>>> + if (supported_status & DRM_GEM_OBJECT_RESIDENT)
>>> + print_size(p, "resident", region, stats->resident);
>>> +
>>> + if (supported_status & DRM_GEM_OBJECT_PURGEABLE)
>>> + print_size(p, "purgeable", region, stats->purgeable);
>>> +}
>>> +EXPORT_SYMBOL(drm_print_memory_stats);
>>> +
>>> +/**
>>> + * drm_show_memory_stats - Helper to collect and show standard fdinfo memory stats
>>> + * @p: the printer to print output to
>>> + * @file: the DRM file
>>> + *
>>> + * Helper to iterate over GEM objects with a handle allocated in the specified
>>> + * file.
>>> + */
>>> +void drm_show_memory_stats(struct drm_printer *p, struct drm_file *file)
>>> +{
>>> + struct drm_gem_object *obj;
>>> + struct drm_memory_stats status = {};
>>> + enum drm_gem_object_status supported_status;
>>> + int id;
>>> +
>>> + spin_lock(&file->table_lock);
>>> + idr_for_each_entry (&file->object_idr, obj, id) {
>>> + enum drm_gem_object_status s = 0;
>>> +
>>> + if (obj->funcs && obj->funcs->status) {
>>> + s = obj->funcs->status(obj);
>>> + supported_status = DRM_GEM_OBJECT_RESIDENT |
>>> + DRM_GEM_OBJECT_PURGEABLE;
>>
>> Whats the purpose of supported_status? It is never modified. Did you
>> intend for the vfunc to be returning this?
>
> for now, simply to avoid showing fields for drivers which don't
> support the vfunc.. it could be made more fine grained later if the
> need arises.

I think if vfunc returned a bitmask of supported statuses that would be
better.

>>> + }
>>> +
>>> + if (obj->handle_count > 1) {
>>> + status.shared += obj->size;
>>> + } else {
>>> + status.private += obj->size;
>>> + }
>>> +
>>> + if (s & DRM_GEM_OBJECT_RESIDENT) {
>>> + status.resident += obj->size;
>>> + } else {
>>> + /* If already purged or not yet backed by pages, don't
>>> + * count it as purgeable:
>>> + */
>>> + s &= ~DRM_GEM_OBJECT_PURGEABLE;
>>> + }
>>
>> Again, why couldn't a resident object also be purgeable?
>
> it is the other way around.. if it isn't backed by pages (ie. already
> purged, etc) it shouldn't count as purgeable

Oops, may bad.

>>> +
>>> + if (!dma_resv_test_signaled(obj->resv, dma_resv_usage_rw(true))) {
>>> + status.active += obj->size;
>>> +
>>> + /* If still active, don't count as purgeable: */
>>> + s &= ~DRM_GEM_OBJECT_PURGEABLE;
>>
>> Also add it to resident if driver hasn't advertised
>> DRM_GEM_OBJECT_RESIDENT? Not much value so not sure.
>>
>>> + }
>>> +
>>> + if (s & DRM_GEM_OBJECT_PURGEABLE)
>>> + status.purgeable += obj->size;
>>> + }
>>> + spin_unlock(&file->table_lock);
>>> +
>>> + drm_print_memory_stats(p, &status, supported_status, "memory");
>>> +}
>>> +EXPORT_SYMBOL(drm_show_memory_stats);
>>> +
>>> /**
>>> * drm_show_fdinfo - helper for drm file fops
>>> - * @seq_file: output stream
>>> + * @m: output stream
>>> * @f: the device file instance
>>> *
>>> * Helper to implement fdinfo, for userspace to query usage stats, etc, of a
>>> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
>>> index 6de6d0e9c634..1339e925af52 100644
>>> --- a/include/drm/drm_file.h
>>> +++ b/include/drm/drm_file.h
>>> @@ -41,6 +41,7 @@
>>> struct dma_fence;
>>> struct drm_file;
>>> struct drm_device;
>>> +struct drm_printer;
>>> struct device;
>>> struct file;
>>>
>>> @@ -440,6 +441,24 @@ void drm_send_event(struct drm_device *dev, struct drm_pending_event *e);
>>> void drm_send_event_timestamp_locked(struct drm_device *dev,
>>> struct drm_pending_event *e,
>>> ktime_t timestamp);
>>> +
>>> +
>>> +struct drm_memory_stats {
>>> + size_t shared;
>>> + size_t private;
>>> + size_t resident;
>>> + size_t purgeable;
>>> + size_t active;
>>> +};
>>
>> Is size_t enough? I'd be tempted to just make it u64.
>
> hmm, >4GB VRAM on 32b system? Seems dubious but I guess u64 would be
> fine too...

Or just two ioctls to overflow it with any driver which does delayed/on
first use allocation?

Regards,

Tvrtko

>>> +
>>> +enum drm_gem_object_status;
>>> +
>>> +void drm_print_memory_stats(struct drm_printer *p,
>>> + const struct drm_memory_stats *stats,
>>> + enum drm_gem_object_status supported_status,
>>> + const char *region);
>>> +
>>> +void drm_show_memory_stats(struct drm_printer *p, struct drm_file *file);
>>> void drm_show_fdinfo(struct seq_file *m, struct file *f);
>>>
>>> struct file *mock_drm_getfile(struct drm_minor *minor, unsigned int flags);
>>> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
>>> index 189fd618ca65..9ebd2820ad1f 100644
>>> --- a/include/drm/drm_gem.h
>>> +++ b/include/drm/drm_gem.h
>>> @@ -42,6 +42,25 @@
>>> struct iosys_map;
>>> struct drm_gem_object;
>>>
>>> +/**
>>> + * enum drm_gem_object_status - bitmask of object state for fdinfo reporting
>>> + * @DRM_GEM_OBJECT_RESIDENT: object is resident in memory (ie. not unpinned)
>>> + * @DRM_GEM_OBJECT_PURGEABLE: object marked as purgeable by userspace
>>> + *
>>> + * Bitmask of status used for fdinfo memory stats, see &drm_gem_object_funcs.status
>>> + * and drm_show_fdinfo(). Note that an object can DRM_GEM_OBJECT_PURGEABLE if
>>
>> can be
>>
>>> + * it still active or not resident, in which case drm_show_fdinfo() will not
>> it is
>>
>>> + * account for it as purgeable. So drivers do not need to check if the buffer
>>> + * is idle and resident to return this bit. (Ie. userspace can mark a buffer
>>> + * as purgeable even while it is still busy on the GPU.. it does not _actually_
>>> + * become puregeable until it becomes idle. The status gem object func does
>>> + * not need to consider this.)
>>> + */
>>> +enum drm_gem_object_status {
>>> + DRM_GEM_OBJECT_RESIDENT = BIT(0),
>>> + DRM_GEM_OBJECT_PURGEABLE = BIT(1),
>>> +};
>>
>> Why enum for a bitmask?
>
> I guess personal preference, #define's have no type so they aren't
> linked to the variable
>
>>> +
>>> /**
>>> * struct drm_gem_object_funcs - GEM object functions
>>> */
>>> @@ -174,6 +193,17 @@ struct drm_gem_object_funcs {
>>> */
>>> int (*evict)(struct drm_gem_object *obj);
>>>
>>> + /**
>>> + * @status:
>>> + *
>>> + * The optional status callback can return additional object state
>>> + * which determines which stats the object is counted against. The
>>> + * callback is called under table_lock. Racing against object status
>>> + * change is "harmless", and the callback can expect to not race
>>> + * against object destruction.
>>> + */
>>> + enum drm_gem_object_status (*status)(struct drm_gem_object *obj);
>>
>> Why not have this under driver vfuncs? Can you see an usecase where it
>> needs to be per object?
>
> Probably doesn't need to be per object, but putting it in obj vfuncs
> lets the driver keep it static in their foo_gem_stuff.c
>
>> Modulo the details ie. on the high level I think this works. More
>> advanced drivers can re-use the exported drm_print_memory_stats and
>> amount of sharing-vs-duplication seems similar to my proposal so again,
>> I think it is an okay approach.
>
> yup, this was the intent w/ drm_print_memory_stats()
>
> BR,
> -R
>
>> Regards,
>>
>> Tvrtko
>>
>>> +
>>> /**
>>> * @vm_ops:
>>> *