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Message-ID: <CAF6AEGsWtJs2xcZx59P9_maxn1RqCO6-4GwEp2fL31bZtTyuoA@mail.gmail.com>
Date: Fri, 5 Apr 2024 10:59:17 -0700
From: Rob Clark <robdclark@...il.com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
Hans de Goede <hdegoede@...hat.com>, kernel@...labora.com,
Boris Brezillon <boris.brezillon@...labora.com>, Tvrtko Ursulin <tursulin@...ulin.net>,
Christopher Healy <healych@...zon.com>, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/sysfs: Add drm class-wide attribute to get active
device clients
On Wed, Apr 3, 2024 at 11:37 AM Adrián Larumbe
<adrian.larumbe@...labora.com> wrote:
>
> Up to this day, all fdinfo-based GPU profilers must traverse the entire
> /proc directory structure to find open DRM clients with fdinfo file
> descriptors. This is inefficient and time-consuming.
>
> This patch adds a new device class attribute that will install a sysfs file
> per DRM device, which can be queried by profilers to get a list of PIDs for
> their open clients. This file isn't human-readable, and it's meant to be
> queried only by GPU profilers like gputop and nvtop.
>
> Cc: Boris Brezillon <boris.brezillon@...labora.com>
> Cc: Tvrtko Ursulin <tursulin@...ulin.net>
> Cc: Christopher Healy <healych@...zon.com>
> Signed-off-by: Adrián Larumbe <adrian.larumbe@...labora.com>
It does seem like a good idea.. idk if there is some precedent to
prefer binary vs ascii in sysfs, but having a way to avoid walking
_all_ processes is a good idea.
BR,
-R
> ---
> drivers/gpu/drm/drm_internal.h | 2 +-
> drivers/gpu/drm/drm_privacy_screen.c | 2 +-
> drivers/gpu/drm/drm_sysfs.c | 89 ++++++++++++++++++++++------
> 3 files changed, 74 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
> index 2215baef9a3e..9a399b03d11c 100644
> --- a/drivers/gpu/drm/drm_internal.h
> +++ b/drivers/gpu/drm/drm_internal.h
> @@ -145,7 +145,7 @@ bool drm_master_internal_acquire(struct drm_device *dev);
> void drm_master_internal_release(struct drm_device *dev);
>
> /* drm_sysfs.c */
> -extern struct class *drm_class;
> +extern struct class drm_class;
>
> int drm_sysfs_init(void);
> void drm_sysfs_destroy(void);
> diff --git a/drivers/gpu/drm/drm_privacy_screen.c b/drivers/gpu/drm/drm_privacy_screen.c
> index 6cc39e30781f..2fbd24ba5818 100644
> --- a/drivers/gpu/drm/drm_privacy_screen.c
> +++ b/drivers/gpu/drm/drm_privacy_screen.c
> @@ -401,7 +401,7 @@ struct drm_privacy_screen *drm_privacy_screen_register(
> mutex_init(&priv->lock);
> BLOCKING_INIT_NOTIFIER_HEAD(&priv->notifier_head);
>
> - priv->dev.class = drm_class;
> + priv->dev.class = &drm_class;
> priv->dev.type = &drm_privacy_screen_type;
> priv->dev.parent = parent;
> priv->dev.release = drm_privacy_screen_device_release;
> diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
> index a953f69a34b6..56ca9e22c720 100644
> --- a/drivers/gpu/drm/drm_sysfs.c
> +++ b/drivers/gpu/drm/drm_sysfs.c
> @@ -58,8 +58,6 @@ static struct device_type drm_sysfs_device_connector = {
> .name = "drm_connector",
> };
>
> -struct class *drm_class;
> -
> #ifdef CONFIG_ACPI
> static bool drm_connector_acpi_bus_match(struct device *dev)
> {
> @@ -128,6 +126,62 @@ static const struct component_ops typec_connector_ops = {
>
> static CLASS_ATTR_STRING(version, S_IRUGO, "drm 1.1.0 20060810");
>
> +static ssize_t clients_show(struct device *cd, struct device_attribute *attr, char *buf)
> +{
> + struct drm_minor *minor = cd->driver_data;
> + struct drm_device *ddev = minor->dev;
> + struct drm_file *priv;
> + ssize_t offset = 0;
> + void *pid_buf;
> +
> + if (minor->type != DRM_MINOR_RENDER)
> + return 0;
> +
> + pid_buf = kvmalloc(PAGE_SIZE, GFP_KERNEL);
> + if (!pid_buf)
> + return 0;
> +
> + mutex_lock(&ddev->filelist_mutex);
> + list_for_each_entry_reverse(priv, &ddev->filelist, lhead) {
> + struct pid *pid;
> +
> + if (drm_WARN_ON(ddev, (PAGE_SIZE - offset) < sizeof(pid_t)))
> + break;
> +
> + rcu_read_lock();
> + pid = rcu_dereference(priv->pid);
> + (*(pid_t *)(pid_buf + offset)) = pid_vnr(pid);
> + rcu_read_unlock();
> +
> + offset += sizeof(pid_t);
> + }
> + mutex_unlock(&ddev->filelist_mutex);
> +
> + if (offset < PAGE_SIZE)
> + (*(pid_t *)(pid_buf + offset)) = 0;
> +
> + memcpy(buf, pid_buf, offset);
> +
> + kvfree(pid_buf);
> +
> + return offset;
> +
> +}
> +static DEVICE_ATTR_RO(clients);
> +
> +static struct attribute *drm_device_attrs[] = {
> + &dev_attr_clients.attr,
> + NULL,
> +};
> +ATTRIBUTE_GROUPS(drm_device);
> +
> +struct class drm_class = {
> + .name = "drm",
> + .dev_groups = drm_device_groups,
> +};
> +
> +static bool drm_class_initialised;
> +
> /**
> * drm_sysfs_init - initialize sysfs helpers
> *
> @@ -142,18 +196,19 @@ int drm_sysfs_init(void)
> {
> int err;
>
> - drm_class = class_create("drm");
> - if (IS_ERR(drm_class))
> - return PTR_ERR(drm_class);
> + err = class_register(&drm_class);
> + if (err)
> + return err;
>
> - err = class_create_file(drm_class, &class_attr_version.attr);
> + err = class_create_file(&drm_class, &class_attr_version.attr);
> if (err) {
> - class_destroy(drm_class);
> - drm_class = NULL;
> + class_destroy(&drm_class);
> return err;
> }
>
> - drm_class->devnode = drm_devnode;
> + drm_class.devnode = drm_devnode;
> +
> + drm_class_initialised = true;
>
> drm_sysfs_acpi_register();
> return 0;
> @@ -166,12 +221,12 @@ int drm_sysfs_init(void)
> */
> void drm_sysfs_destroy(void)
> {
> - if (IS_ERR_OR_NULL(drm_class))
> + if (!drm_class_initialised)
> return;
> drm_sysfs_acpi_unregister();
> - class_remove_file(drm_class, &class_attr_version.attr);
> - class_destroy(drm_class);
> - drm_class = NULL;
> + class_remove_file(&drm_class, &class_attr_version.attr);
> + class_destroy(&drm_class);
> + drm_class_initialised = false;
> }
>
> static void drm_sysfs_release(struct device *dev)
> @@ -372,7 +427,7 @@ int drm_sysfs_connector_add(struct drm_connector *connector)
> return -ENOMEM;
>
> device_initialize(kdev);
> - kdev->class = drm_class;
> + kdev->class = &drm_class;
> kdev->type = &drm_sysfs_device_connector;
> kdev->parent = dev->primary->kdev;
> kdev->groups = connector_dev_groups;
> @@ -550,7 +605,7 @@ struct device *drm_sysfs_minor_alloc(struct drm_minor *minor)
> minor_str = "card%d";
>
> kdev->devt = MKDEV(DRM_MAJOR, minor->index);
> - kdev->class = drm_class;
> + kdev->class = &drm_class;
> kdev->type = &drm_sysfs_device_minor;
> }
>
> @@ -579,10 +634,10 @@ struct device *drm_sysfs_minor_alloc(struct drm_minor *minor)
> */
> int drm_class_device_register(struct device *dev)
> {
> - if (!drm_class || IS_ERR(drm_class))
> + if (!drm_class_initialised)
> return -ENOENT;
>
> - dev->class = drm_class;
> + dev->class = &drm_class;
> return device_register(dev);
> }
> EXPORT_SYMBOL_GPL(drm_class_device_register);
>
> base-commit: 45c734fdd43db14444025910b4c59dd2b8be714a
> --
> 2.44.0
>
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