[RFC 3/6] drm: Add fdinfo memory stats

[Tvrtko Ursulin]

On 17/04/2023 17:20, Christian König wrote:
> Am 17.04.23 um 17:56 schrieb Tvrtko Ursulin:
>> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>>
>> Add support to dump GEM stats to fdinfo.
>>
>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>> ---
>>   Documentation/gpu/drm-usage-stats.rst | 12 +++++++
>>   drivers/gpu/drm/drm_file.c            | 52 +++++++++++++++++++++++++++
>>   include/drm/drm_drv.h                 |  7 ++++
>>   include/drm/drm_file.h                |  8 +++++
>>   4 files changed, 79 insertions(+)
>>
>> diff --git a/Documentation/gpu/drm-usage-stats.rst 
>> b/Documentation/gpu/drm-usage-stats.rst
>> index 2ab32c40e93c..8273a41b2fb0 100644
>> --- a/Documentation/gpu/drm-usage-stats.rst
>> +++ b/Documentation/gpu/drm-usage-stats.rst
>> @@ -21,6 +21,7 @@ File format specification
>>   - File shall contain one key value pair per one line of text.
>>   - Colon character (`:`) must be used to delimit keys and values.
>> +- Caret (`^`) is also a reserved character.
>>   - All keys shall be prefixed with `drm-`.
>>   - Whitespace between the delimiter and first non-whitespace 
>> character shall be
>>     ignored when parsing.
>> @@ -105,6 +106,17 @@ 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-memory-<str>^size:      <uint> [KiB|MiB]
>> +- drm-memory-<str>^shared:    <uint> [KiB|MiB]
>> +- drm-memory-<str>^resident:  <uint> [KiB|MiB]
>> +- drm-memory-<str>^purgeable: <uint> [KiB|MiB]
>> +- drm-memory-<str>^active:    <uint> [KiB|MiB]
> 
> What exactly does size/shared/active mean here?
> 
> If it means what I think it does I don't see how TTM based drivers 
> should track that in the first place.

Size is an analogue to process VM size - maximum reachable/allocated 
memory belonging to a client.

Shared could be IMO viewed as a bit dodgy and either could be dropped or 
needs to be better defined. For now I simply followed the implementation 
from Rob's RFC which is:

	if (obj->handle_count > 1)
		stats[0].shared += sz;

I can see some usefulness to it but haven't thought much about semantics 
yet.

Similar story with active which I think is not very useful. 
Implementation is like this:

	if (!dma_resv_test_signaled(obj->resv, dma_resv_usage_rw(true)))
		stats[0].active += sz;

For me it is too transient to bring much value over the resident 
category. I supposed only advantage is that resident (as does purgeable) 
needs driver cooperation while active can be done like about from DRM 
core. Although I am not a big fan of counting these stats from the core 
to begin with..

Regards,

Tvrtko

>> +Resident category is identical to the drm-memory-<str> key and two 
>> should be
>> +mutually exclusive.
>> +
>> +TODO more description text...
>> +
>>   - drm-cycles-<str> <uint>
>>   Engine identifier string must be the same as the one specified in the
>> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
>> index 37b4f76a5191..e202f79e816d 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"
>> @@ -871,6 +872,54 @@ void drm_send_event(struct drm_device *dev, 
>> struct drm_pending_event *e)
>>   }
>>   EXPORT_SYMBOL(drm_send_event);
>> +static void
>> +print_stat(struct drm_printer *p, const char *stat, const char 
>> *region, u64 sz)
>> +{
>> +    const char *units[] = {"", " KiB", " MiB"};
>> +    unsigned int u;
>> +
>> +    if (sz == ~0ull) /* Not supported by the driver. */
>> +        return;
>> +
>> +    for (u = 0; u < ARRAY_SIZE(units) - 1; u++) {
>> +        if (sz < SZ_1K)
>> +            break;
>> +        sz = div_u64(sz, SZ_1K);
>> +    }
>> +
>> +    drm_printf(p, "drm-memory-%s^%s:\t%llu%s\n",
>> +           region, stat, sz, units[u]);
>> +}
>> +
>> +static void print_memory_stats(struct drm_printer *p, struct drm_file 
>> *file)
>> +{
>> +    struct drm_device *dev = file->minor->dev;
>> +    struct drm_fdinfo_memory_stat *stats;
>> +    unsigned int num, i;
>> +    char **regions;
>> +
>> +    regions = dev->driver->query_fdinfo_memory_regions(dev, &num);
>> +
>> +    stats = kcalloc(num, sizeof(*stats), GFP_KERNEL);
>> +    if (!stats)
>> +        return;
>> +
>> +    dev->driver->query_fdinfo_memory_stats(file, stats);
>> +
>> +    for (i = 0; i < num; i++) {
>> +        if (!regions[i]) /* Allow sparse name arrays. */
>> +            continue;
>> +
>> +        print_stat(p, "size", regions[i], stats[i].size);
>> +        print_stat(p, "shared", regions[i], stats[i].shared);
>> +        print_stat(p, "resident", regions[i], stats[i].resident);
>> +        print_stat(p, "purgeable", regions[i], stats[i].purgeable);
>> +        print_stat(p, "active", regions[i], stats[i].active);
>> +    }
>> +
>> +    kfree(stats);
>> +}
>> +
>>   /**
>>    * drm_show_fdinfo - helper for drm file fops
>>    * @seq_file: output stream
>> @@ -900,6 +949,9 @@ void drm_show_fdinfo(struct seq_file *m, struct 
>> file *f)
>>       if (dev->driver->show_fdinfo)
>>           dev->driver->show_fdinfo(&p, file);
>> +
>> +    if (dev->driver->query_fdinfo_memory_regions)
>> +        print_memory_stats(&p, file);
>>   }
>>   EXPORT_SYMBOL(drm_show_fdinfo);
>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
>> index 89e2706cac56..ccc1cd98d2aa 100644
>> --- a/include/drm/drm_drv.h
>> +++ b/include/drm/drm_drv.h
>> @@ -35,6 +35,7 @@
>>   #include <drm/drm_device.h>
>>   struct drm_file;
>> +struct drm_fdinfo_memory_stat;
>>   struct drm_gem_object;
>>   struct drm_master;
>>   struct drm_minor;
>> @@ -408,6 +409,12 @@ struct drm_driver {
>>        */
>>       void (*show_fdinfo)(struct drm_printer *p, struct drm_file *f);
>> +    char ** (*query_fdinfo_memory_regions)(struct drm_device *dev,
>> +                           unsigned int *num);
>> +
>> +    void (*query_fdinfo_memory_stats)(struct drm_file *f,
>> +                      struct drm_fdinfo_memory_stat *stat);
>> +
>>       /** @major: driver major number */
>>       int major;
>>       /** @minor: driver minor number */
>> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
>> index 7d9b3c65cbc1..00d48beeac5c 100644
>> --- a/include/drm/drm_file.h
>> +++ b/include/drm/drm_file.h
>> @@ -375,6 +375,14 @@ struct drm_file {
>>   #endif
>>   };
>> +struct drm_fdinfo_memory_stat {
>> +    u64 size;
>> +    u64 shared;
>> +    u64 resident;
>> +    u64 purgeable;
>> +    u64 active;
>> +};
>> +
>>   /**
>>    * drm_is_primary_client - is this an open file of the primary node
>>    * @file_priv: DRM file
>