On 05/04/2024 18:59, Rob Clark wrote:
On Wed, Apr 3, 2024 at 11:37 AM Adrián Larumbe
<adrian.larumbe@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tursulin@xxxxxxxxxxx>
Cc: Christopher Healy <healych@xxxxxxxxxx>
Signed-off-by: Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx>
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.
I naturally second that it is a needed feature, but I do not think
binary format is justified. AFAIR it should be used for things like
hw/fw standardised tables or firmware images, not when exporting a
simple list of PIDs. It also precludes easy shell/script access and the
benefit of avoiding parsing a short list is I suspect completely dwarfed
by needing to parse all the related fdinfo etc.
---
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;
Why this?
+
+ pid_buf = kvmalloc(PAGE_SIZE, GFP_KERNEL);
I don't quite get the kvmalloc for just one page (or why even a temporay
buffer and not write into buf directly?).
+ 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;
Feels bad.. I would suggest exploring implementing a read callback
(instead of show) and handling arbitrary size output.
+
+ 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;
Either NULL terminated or PAGE_SIZE/sizeof(pid) entries and not NULL
terminated feels weird. If I got that right.
For me everything points towards going for text output.
+
+ memcpy(buf, pid_buf, offset);
+
+ kvfree(pid_buf);
+
+ return offset;
+
+}
+static DEVICE_ATTR_RO(clients);
Shouldn't BIN_ATTR_RO be used for binary files in sysfs?
Regards,
Tvrtko
P.S. Or maybe it is time for drmfs? Where each client gets a directory
and drivers can populate files. Such as per client logging streams and
whatnot.
+
+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
