[RFC] drm/msm: Add GPU memory traces

[Gurchetan Singh]

On Fri, Mar 1, 2024 at 10:54 AM Rob Clark <robdclark at gmail.com> wrote:

> From: Rob Clark <robdclark at chromium.org>
>
> Perfetto can use these traces to track global and per-process GPU memory
> usage.
>
> Signed-off-by: Rob Clark <robdclark at chromium.org>
> ---
> I realized the tracepoint that perfetto uses to show GPU memory usage
> globally and per-process was already upstream, but with no users.
>
> This overlaps a bit with fdinfo, but ftrace is a lighter weight
> mechanism and fits better with perfetto (plus is already supported in
> trace_processor and perfetto UI, whereas something fdinfo based would
> require new code to be added in perfetto.
>
> We could probably do this more globally (ie. drm_gem_get/put_pages() and
> drm_gem_handle_create_tail()/drm_gem_object_release_handle() if folks
> prefer.  Not sure where that leaves the TTM drivers.
>
>  drivers/gpu/drm/msm/Kconfig   |  1 +
>  drivers/gpu/drm/msm/msm_drv.h |  5 +++++
>  drivers/gpu/drm/msm/msm_gem.c | 37 +++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/msm/msm_gpu.h |  8 ++++++++
>  4 files changed, 51 insertions(+)
>
> diff --git a/drivers/gpu/drm/msm/Kconfig b/drivers/gpu/drm/msm/Kconfig
> index f202f26adab2..e4c912fcaf22 100644
> --- a/drivers/gpu/drm/msm/Kconfig
> +++ b/drivers/gpu/drm/msm/Kconfig
> @@ -33,6 +33,7 @@ config DRM_MSM
>         select PM_OPP
>         select NVMEM
>         select PM_GENERIC_DOMAINS
> +       select TRACE_GPU_MEM
>         help
>           DRM/KMS driver for MSM/snapdragon.
>
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index 16a7cbc0b7dd..cb8f7e804b5b 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/drivers/gpu/drm/msm/msm_drv.h
> @@ -137,6 +137,11 @@ struct msm_drm_private {
>         struct msm_rd_state *hangrd;   /* debugfs to dump hanging submits
> */
>         struct msm_perf_state *perf;
>
> +       /**
> +        * total_mem: Total/global amount of memory backing GEM objects.
> +        */
> +       atomic64_t total_mem;
> +
>         /**
>          * List of all GEM objects (mainly for debugfs, protected by
> obj_lock
>          * (acquire before per GEM object lock)
> diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
> index 175ee4ab8a6f..e04c4af5d154 100644
> --- a/drivers/gpu/drm/msm/msm_gem.c
> +++ b/drivers/gpu/drm/msm/msm_gem.c
> @@ -12,6 +12,9 @@
>  #include <linux/pfn_t.h>
>
>  #include <drm/drm_prime.h>
> +#include <drm/drm_file.h>
> +
> +#include <trace/events/gpu_mem.h>
>
>  #include "msm_drv.h"
>  #include "msm_fence.h"
> @@ -33,6 +36,34 @@ static bool use_pages(struct drm_gem_object *obj)
>         return !msm_obj->vram_node;
>  }
>
> +static void update_device_mem(struct msm_drm_private *priv, ssize_t size)
> +{
> +       uint64_t total_mem = atomic64_add_return(size, &priv->total_mem);
> +       trace_gpu_mem_total(0, 0, total_mem);
> +}
> +
> +static void update_ctx_mem(struct drm_file *file, ssize_t size)
> +{
> +       struct msm_file_private *ctx = file->driver_priv;
> +       uint64_t ctx_mem = atomic64_add_return(size, &ctx->ctx_mem);
> +
> +       rcu_read_lock(); /* Locks file->pid! */
> +       trace_gpu_mem_total(0, pid_nr(file->pid), ctx_mem);
> +       rcu_read_unlock();
> +
> +}
> +
> +static int msm_gem_open(struct drm_gem_object *obj, struct drm_file *file)
> +{
> +       update_ctx_mem(file, obj->size);
> +       return 0;
> +}
> +
> +static void msm_gem_close(struct drm_gem_object *obj, struct drm_file
> *file)
> +{
> +       update_ctx_mem(file, -obj->size);
> +}
> +
>  /*
>   * Cache sync.. this is a bit over-complicated, to fit dma-mapping
>   * API.  Really GPU cache is out of scope here (handled on cmdstream)
> @@ -156,6 +187,8 @@ static struct page **get_pages(struct drm_gem_object
> *obj)
>                         return p;
>                 }
>
> +               update_device_mem(dev->dev_private, obj->size);
> +
>                 msm_obj->pages = p;
>
>                 msm_obj->sgt = drm_prime_pages_to_sg(obj->dev, p, npages);
> @@ -209,6 +242,8 @@ static void put_pages(struct drm_gem_object *obj)
>                         msm_obj->sgt = NULL;
>                 }
>
> +               update_device_mem(obj->dev->dev_private, -obj->size);
> +
>                 if (use_pages(obj))
>                         drm_gem_put_pages(obj, msm_obj->pages, true,
> false);
>                 else
> @@ -1118,6 +1153,8 @@ static const struct vm_operations_struct vm_ops = {
>
>  static const struct drm_gem_object_funcs msm_gem_object_funcs = {
>         .free = msm_gem_free_object,
> +       .open = msm_gem_open,
> +       .close = msm_gem_close,
>         .pin = msm_gem_prime_pin,
>         .unpin = msm_gem_prime_unpin,
>         .get_sg_table = msm_gem_prime_get_sg_table,
> diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
> index 2bfcb222e353..f7d2a7d6f8cc 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.h
> +++ b/drivers/gpu/drm/msm/msm_gpu.h
> @@ -428,6 +428,14 @@ struct msm_file_private {
>          * level.
>          */
>         struct drm_sched_entity *entities[NR_SCHED_PRIORITIES *
> MSM_GPU_MAX_RINGS];
> +
> +       /**
> +        * ctx_mem:
> +        *
> +        * Total amount of memory of GEM buffers with handles attached for
> +        * this context.
> +        */
> +       atomic64_t ctx_mem;
>  };
>


Just for added context, past discussions on TRACE_GPU_MEM:

https://lists.freedesktop.org/archives/dri-devel/2021-October/328260.html
https://lists.freedesktop.org/archives/dri-devel/2021-January/295120.html

Some have even suggested deleting the tracepoint altogether.

Personally, I think we should land an internal user in a non-breaking way,
since userspace (Perfetto) already depends on it.  Right now, we're in
limbo for multiple years ...


>  /**
> --
> 2.44.0
>
>
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