[PATCH v2 0/3] Let userspace know about swapped out panthor GEM objects

[PATCH v2 0/3] Let userspace know about swapped out panthor GEM objects

[Nicolas Frattaroli]

Panthor has recently gained a GEM shrinker. It allows evicting memory
that backs unused GEM objects to swap.

In this series, both fdinfo and Panthor's gems debugfs are extended so
that information on evicted pages can be gathered by users through these
two methods.

---
Changes in v2:
- Change reclaimed_count to saturate at INT_MAX
- Add "evictions" column to panthor gems debugfs which prints
  reclaimed_count
- Add a patch to reduce the padding of one panthor gems debugfs column a
  bit
- Link to v1: https://patch.msgid.link/20260420-panthor-bo-reclaim-observability-v1-0-a4d1a36ee84f@collabora.com

To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
To: Maxime Ripard <mripard@kernel.org>
To: Thomas Zimmermann <tzimmermann@suse.de>
To: David Airlie <airlied@gmail.com>
To: Simona Vetter <simona@ffwll.ch>
To: Boris Brezillon <boris.brezillon@collabora.com>
To: Steven Price <steven.price@arm.com>
To: Liviu Dudau <liviu.dudau@arm.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org
Cc: kernel@collabora.com
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

---
Nicolas Frattaroli (3):
      drm/fdinfo: Add "evicted" memory accounting
      drm/panthor: Implement evicted status for GEM objects
      drm/panthor: Reduce padding in gems debugfs for refcount

 drivers/gpu/drm/drm_file.c            |  8 ++++++++
 drivers/gpu/drm/panthor/panthor_gem.c | 18 ++++++++++++++----
 drivers/gpu/drm/panthor/panthor_gem.h | 10 ++++++++++
 include/drm/drm_file.h                |  2 ++
 include/drm/drm_gem.h                 |  2 ++
 5 files changed, 36 insertions(+), 4 deletions(-)
---
base-commit: 3f9357c30a44734d45e3093c521d52b2aefb09f5
change-id: 20260420-panthor-bo-reclaim-observability-970679c9533c

Best regards,
--  
Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

[PATCH v2 1/3] drm/fdinfo: Add "evicted" memory accounting

[Nicolas Frattaroli]

Currently, there's no way to know for certain how much GPU memory was
swapped out. The difference between total and resident memory would
include newly allocated pages, which are not resident, but also aren't
swapped out.

Add a new drm_gem_object_status so drivers can signal when an object has
been evicted to swap, and add a new "evicted" counter to
drm_memory_stats.

Due to how the supported_flags bitmask is determined, the "evicted"
count won't be printed to fdinfo if there's no swapped out pages.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
---
 drivers/gpu/drm/drm_file.c | 8 ++++++++
 include/drm/drm_file.h     | 2 ++
 include/drm/drm_gem.h      | 2 ++
 3 files changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index ec820686b302..5078172976c0 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -868,6 +868,7 @@ int drm_memory_stats_is_zero(const struct drm_memory_stats *stats)
 		stats->private == 0 &&
 		stats->resident == 0 &&
 		stats->purgeable == 0 &&
+		stats->evicted == 0 &&
 		stats->active == 0);
 }
 EXPORT_SYMBOL(drm_memory_stats_is_zero);
@@ -901,6 +902,10 @@ void drm_print_memory_stats(struct drm_printer *p,
 	if (supported_status & DRM_GEM_OBJECT_PURGEABLE)
 		drm_fdinfo_print_size(p, prefix, "purgeable", region,
 				      stats->purgeable);
+
+	if (supported_status & DRM_GEM_OBJECT_EVICTED)
+		drm_fdinfo_print_size(p, prefix, "evicted", region,
+				      stats->evicted);
 }
 EXPORT_SYMBOL(drm_print_memory_stats);
 
@@ -954,6 +959,9 @@ void drm_show_memory_stats(struct drm_printer *p, struct drm_file *file)
 
 		if (s & DRM_GEM_OBJECT_PURGEABLE)
 			status.purgeable += add_size;
+
+		if (s & DRM_GEM_OBJECT_EVICTED)
+			status.evicted += add_size;
 	}
 	spin_unlock(&file->table_lock);
 
diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
index 6ee70ad65e1f..213dfecac342 100644
--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -500,6 +500,7 @@ void drm_send_event_timestamp_locked(struct drm_device *dev,
  * @resident: Total size of GEM objects backing pages
  * @purgeable: Total size of GEM objects that can be purged (resident and not active)
  * @active: Total size of GEM objects active on one or more engines
+ * @evicted: Total size of GEM objects that have been evicted to swap
  *
  * Used by drm_print_memory_stats()
  */
@@ -509,6 +510,7 @@ struct drm_memory_stats {
 	u64 resident;
 	u64 purgeable;
 	u64 active;
+	u64 evicted;
 };
 
 enum drm_gem_object_status;
diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
index 86f5846154f7..b42ea2e582cf 100644
--- a/include/drm/drm_gem.h
+++ b/include/drm/drm_gem.h
@@ -53,6 +53,7 @@ struct drm_gem_object;
  * @DRM_GEM_OBJECT_RESIDENT: object is resident in memory (ie. not unpinned)
  * @DRM_GEM_OBJECT_PURGEABLE: object marked as purgeable by userspace
  * @DRM_GEM_OBJECT_ACTIVE: object is currently used by an active submission
+ * @DRM_GEM_OBJECT_EVICTED: object is evicted to swap
  *
  * Bitmask of status used for fdinfo memory stats, see &drm_gem_object_funcs.status
  * and drm_show_fdinfo().  Note that an object can report DRM_GEM_OBJECT_PURGEABLE
@@ -67,6 +68,7 @@ enum drm_gem_object_status {
 	DRM_GEM_OBJECT_RESIDENT  = BIT(0),
 	DRM_GEM_OBJECT_PURGEABLE = BIT(1),
 	DRM_GEM_OBJECT_ACTIVE    = BIT(2),
+	DRM_GEM_OBJECT_EVICTED   = BIT(3),
 };
 
 /**

-- 
2.53.0

Re: [PATCH v2 1/3] drm/fdinfo: Add "evicted" memory accounting

[Steven Price]

On 21/04/2026 11:45, Nicolas Frattaroli wrote:
> Currently, there's no way to know for certain how much GPU memory was
> swapped out. The difference between total and resident memory would
> include newly allocated pages, which are not resident, but also aren't
> swapped out.
> 
> Add a new drm_gem_object_status so drivers can signal when an object has
> been evicted to swap, and add a new "evicted" counter to
> drm_memory_stats.
> 
> Due to how the supported_flags bitmask is determined, the "evicted"
> count won't be printed to fdinfo if there's no swapped out pages.
> 
> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

You should also update the documentation to include this new field
(Documentation/gpu/drm-usage-stats.rst).

Thanks,
Steve

> ---
>  drivers/gpu/drm/drm_file.c | 8 ++++++++
>  include/drm/drm_file.h     | 2 ++
>  include/drm/drm_gem.h      | 2 ++
>  3 files changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> index ec820686b302..5078172976c0 100644
> --- a/drivers/gpu/drm/drm_file.c
> +++ b/drivers/gpu/drm/drm_file.c
> @@ -868,6 +868,7 @@ int drm_memory_stats_is_zero(const struct drm_memory_stats *stats)
>  		stats->private == 0 &&
>  		stats->resident == 0 &&
>  		stats->purgeable == 0 &&
> +		stats->evicted == 0 &&
>  		stats->active == 0);
>  }
>  EXPORT_SYMBOL(drm_memory_stats_is_zero);
> @@ -901,6 +902,10 @@ void drm_print_memory_stats(struct drm_printer *p,
>  	if (supported_status & DRM_GEM_OBJECT_PURGEABLE)
>  		drm_fdinfo_print_size(p, prefix, "purgeable", region,
>  				      stats->purgeable);
> +
> +	if (supported_status & DRM_GEM_OBJECT_EVICTED)
> +		drm_fdinfo_print_size(p, prefix, "evicted", region,
> +				      stats->evicted);
>  }
>  EXPORT_SYMBOL(drm_print_memory_stats);
>  
> @@ -954,6 +959,9 @@ void drm_show_memory_stats(struct drm_printer *p, struct drm_file *file)
>  
>  		if (s & DRM_GEM_OBJECT_PURGEABLE)
>  			status.purgeable += add_size;
> +
> +		if (s & DRM_GEM_OBJECT_EVICTED)
> +			status.evicted += add_size;
>  	}
>  	spin_unlock(&file->table_lock);
>  
> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
> index 6ee70ad65e1f..213dfecac342 100644
> --- a/include/drm/drm_file.h
> +++ b/include/drm/drm_file.h
> @@ -500,6 +500,7 @@ void drm_send_event_timestamp_locked(struct drm_device *dev,
>   * @resident: Total size of GEM objects backing pages
>   * @purgeable: Total size of GEM objects that can be purged (resident and not active)
>   * @active: Total size of GEM objects active on one or more engines
> + * @evicted: Total size of GEM objects that have been evicted to swap
>   *
>   * Used by drm_print_memory_stats()
>   */
> @@ -509,6 +510,7 @@ struct drm_memory_stats {
>  	u64 resident;
>  	u64 purgeable;
>  	u64 active;
> +	u64 evicted;
>  };
>  
>  enum drm_gem_object_status;
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index 86f5846154f7..b42ea2e582cf 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -53,6 +53,7 @@ struct drm_gem_object;
>   * @DRM_GEM_OBJECT_RESIDENT: object is resident in memory (ie. not unpinned)
>   * @DRM_GEM_OBJECT_PURGEABLE: object marked as purgeable by userspace
>   * @DRM_GEM_OBJECT_ACTIVE: object is currently used by an active submission
> + * @DRM_GEM_OBJECT_EVICTED: object is evicted to swap
>   *
>   * Bitmask of status used for fdinfo memory stats, see &drm_gem_object_funcs.status
>   * and drm_show_fdinfo().  Note that an object can report DRM_GEM_OBJECT_PURGEABLE
> @@ -67,6 +68,7 @@ enum drm_gem_object_status {
>  	DRM_GEM_OBJECT_RESIDENT  = BIT(0),
>  	DRM_GEM_OBJECT_PURGEABLE = BIT(1),
>  	DRM_GEM_OBJECT_ACTIVE    = BIT(2),
> +	DRM_GEM_OBJECT_EVICTED   = BIT(3),
>  };
>  
>  /**
> 

Claude review: drm/fdinfo: Add "evicted" memory accounting

[Claude Code Review Bot]

Patch Review

This patch adds `DRM_GEM_OBJECT_EVICTED = BIT(3)` to the status enum, an `evicted` field to `drm_memory_stats`, and wires them into the fdinfo printing/accumulation paths.

**Issue: Missing drm-usage-stats.rst documentation.**
The new `drm-evicted-<region>` key needs an entry in `Documentation/gpu/drm-usage-stats.rst` alongside the existing documented keys. This file explicitly says driver-specific stats "should be documented above and where possible, aligned with other drivers." Since this is being added to the core DRM framework for any driver to use, it's especially important to document the semantics — for example, that evicted is a subset of non-resident memory.

**Minor observation on semantics in `drm_show_memory_stats()`:**
The existing code clears `DRM_GEM_OBJECT_PURGEABLE` when the object is not resident:

```c
if (s & DRM_GEM_OBJECT_RESIDENT) {
    status.resident += add_size;
} else {
    s &= ~DRM_GEM_OBJECT_PURGEABLE;
}
```

The new `DRM_GEM_OBJECT_EVICTED` is accumulated without any filtering. This is correct — evicted objects are by definition not resident, so the semantics are different from purgeable (which is defined as resident + idle + marked). However, the core code doesn't enforce mutual exclusivity between RESIDENT and EVICTED. If a driver were to erroneously return both, both counters would be incremented. This is arguably fine (it's the driver's job to set bits correctly), but a brief comment on the enum doc noting that EVICTED implies non-resident would be helpful.

**Code is correct as written.** The additions to `drm_memory_stats_is_zero()`, `drm_print_memory_stats()`, and `drm_show_memory_stats()` all follow the established pattern.

---
Generated by Claude Code Patch Reviewer

[PATCH v2 2/3] drm/panthor: Implement evicted status for GEM objects

[Nicolas Frattaroli]

For fdinfo to be able to fill its evicted counter with data, panthor
needs to keep track of whether a GEM object has ever been reclaimed.
Just checking whether the pages are resident isn't enough, as newly
allocated objects also won't be resident.

Do this with a new atomic_t member on panthor_gem_object. It's increased
when an object gets evicted by the shrinker, and saturates at INT_MAX.
This means that once an object has been evicted at least once, its
reclaim counter will never return to 0.

Due to this, it's possible to distinguish evicted non-resident pages
from newly allocated non-resident pages by checking whether
reclaimed_count is != 0

Use this new member to then set the appropriate DRM_GEM_OBJECT_EVICTED
status flag for fdinfo.

Also add a new column and status flag to the panthor gems debugfs: the
column is the number of times an object has been evicted, whereas the
flag indicates whether it currently is evicted.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
---
 drivers/gpu/drm/panthor/panthor_gem.c | 18 ++++++++++++++----
 drivers/gpu/drm/panthor/panthor_gem.h | 10 ++++++++++
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
index 69cef05b6ef7..b6fe20b7e6d0 100644
--- a/drivers/gpu/drm/panthor/panthor_gem.c
+++ b/drivers/gpu/drm/panthor/panthor_gem.c
@@ -687,6 +687,8 @@ static void panthor_gem_evict_locked(struct panthor_gem_object *bo)
 	if (drm_WARN_ON_ONCE(bo->base.dev, !bo->backing.pages))
 		return;
 
+	atomic_add_unless(&bo->reclaimed_count, 1, INT_MAX);
+
 	panthor_gem_dev_map_cleanup_locked(bo);
 	panthor_gem_backing_cleanup_locked(bo);
 	panthor_gem_update_reclaim_state_locked(bo, NULL);
@@ -788,6 +790,8 @@ static enum drm_gem_object_status panthor_gem_status(struct drm_gem_object *obj)
 
 	if (drm_gem_is_imported(&bo->base) || bo->backing.pages)
 		res |= DRM_GEM_OBJECT_RESIDENT;
+	else if (atomic_read(&bo->reclaimed_count))
+		res |= DRM_GEM_OBJECT_EVICTED;
 
 	return res;
 }
@@ -1595,6 +1599,7 @@ static void panthor_gem_debugfs_print_flag_names(struct seq_file *m)
 	static const char * const gem_state_flags_names[] = {
 		[PANTHOR_DEBUGFS_GEM_STATE_IMPORTED_BIT] = "imported",
 		[PANTHOR_DEBUGFS_GEM_STATE_EXPORTED_BIT] = "exported",
+		[PANTHOR_DEBUGFS_GEM_STATE_EVICTED_BIT] = "evicted",
 	};
 
 	static const char * const gem_usage_flags_names[] = {
@@ -1625,6 +1630,7 @@ static void panthor_gem_debugfs_bo_print(struct panthor_gem_object *bo,
 {
 	enum panthor_gem_reclaim_state reclaim_state = bo->reclaim_state;
 	unsigned int refcount = kref_read(&bo->base.refcount);
+	int reclaimed_count = atomic_read(&bo->reclaimed_count);
 	char creator_info[32] = {};
 	size_t resident_size;
 	u32 gem_usage_flags = bo->debugfs.flags;
@@ -1638,16 +1644,20 @@ static void panthor_gem_debugfs_bo_print(struct panthor_gem_object *bo,
 
 	snprintf(creator_info, sizeof(creator_info),
 		 "%s/%d", bo->debugfs.creator.process_name, bo->debugfs.creator.tgid);
-	seq_printf(m, "%-32s%-16d%-16d%-16zd%-16zd0x%-16lx",
+	seq_printf(m, "%-32s%-16d%-16d%-11d%-16zd%-16zd0x%-16lx",
 		   creator_info,
 		   bo->base.name,
 		   refcount,
+		   reclaimed_count,
 		   bo->base.size,
 		   resident_size,
 		   drm_vma_node_start(&bo->base.vma_node));
 
 	if (drm_gem_is_imported(&bo->base))
 		gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED;
+	else if (!resident_size && reclaimed_count)
+		gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_EVICTED;
+
 	if (bo->base.dma_buf)
 		gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED;
 
@@ -1671,8 +1681,8 @@ static void panthor_gem_debugfs_print_bos(struct panthor_device *ptdev,
 
 	panthor_gem_debugfs_print_flag_names(m);
 
-	seq_puts(m, "created-by                      global-name     refcount        size            resident-size   file-offset       state      usage       label\n");
-	seq_puts(m, "----------------------------------------------------------------------------------------------------------------------------------------------\n");
+	seq_puts(m, "created-by                      global-name     refcount        evictions  size            resident-size   file-offset       state      usage       label\n");
+	seq_puts(m, "---------------------------------------------------------------------------------------------------------------------------------------------------------\n");
 
 	scoped_guard(mutex, &ptdev->gems.lock) {
 		list_for_each_entry(bo, &ptdev->gems.node, debugfs.node) {
@@ -1680,7 +1690,7 @@ static void panthor_gem_debugfs_print_bos(struct panthor_device *ptdev,
 		}
 	}
 
-	seq_puts(m, "==============================================================================================================================================\n");
+	seq_puts(m, "=========================================================================================================================================================\n");
 	seq_printf(m, "Total size: %zd, Total resident: %zd, Total reclaimable: %zd\n",
 		   totals.size, totals.resident, totals.reclaimable);
 }
diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h
index ae0491d0b121..56d63137b4eb 100644
--- a/drivers/gpu/drm/panthor/panthor_gem.h
+++ b/drivers/gpu/drm/panthor/panthor_gem.h
@@ -19,12 +19,16 @@ struct panthor_vm;
 enum panthor_debugfs_gem_state_flags {
 	PANTHOR_DEBUGFS_GEM_STATE_IMPORTED_BIT = 0,
 	PANTHOR_DEBUGFS_GEM_STATE_EXPORTED_BIT = 1,
+	PANTHOR_DEBUGFS_GEM_STATE_EVICTED_BIT = 2,
 
 	/** @PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED: GEM BO is PRIME imported. */
 	PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED = BIT(PANTHOR_DEBUGFS_GEM_STATE_IMPORTED_BIT),
 
 	/** @PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED: GEM BO is PRIME exported. */
 	PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED = BIT(PANTHOR_DEBUGFS_GEM_STATE_EXPORTED_BIT),
+
+	/** @PANTHOR_DEBUGFS_GEM_STATE_FLAG_EVICTED: GEM BO is evicted to swap. */
+	PANTHOR_DEBUGFS_GEM_STATE_FLAG_EVICTED = BIT(PANTHOR_DEBUGFS_GEM_STATE_EVICTED_BIT),
 };
 
 enum panthor_debugfs_gem_usage_flags {
@@ -172,6 +176,12 @@ struct panthor_gem_object {
 	/** @reclaim_state: Cached reclaim state */
 	enum panthor_gem_reclaim_state reclaim_state;
 
+	/**
+	 * @reclaimed_count: How many times object has been evicted to swap.
+	 * The count saturates at %INT_MAX and will never wrap around to 0.
+	 */
+	atomic_t reclaimed_count;
+
 	/**
 	 * @exclusive_vm_root_gem: Root GEM of the exclusive VM this GEM object
 	 * is attached to.

-- 
2.53.0

Claude review: drm/panthor: Implement evicted status for GEM objects

[Claude Code Review Bot]

Patch Review

This is the meat of the series. It adds `atomic_t reclaimed_count` to `panthor_gem_object`, increments it during eviction, and uses it to report status via both fdinfo and debugfs.

**Correctness of the eviction path ordering is good:**
```c
atomic_add_unless(&bo->reclaimed_count, 1, INT_MAX);

panthor_gem_dev_map_cleanup_locked(bo);
panthor_gem_backing_cleanup_locked(bo);
```
The counter is incremented *before* pages are cleared, which avoids a window where a concurrent lockless reader in `panthor_gem_status()` could see the object as neither resident nor evicted. This is the right order.

**The status callback logic is correct:**
```c
if (drm_gem_is_imported(&bo->base) || bo->backing.pages)
    res |= DRM_GEM_OBJECT_RESIDENT;
else if (atomic_read(&bo->reclaimed_count))
    res |= DRM_GEM_OBJECT_EVICTED;
```
The `else if` correctly makes RESIDENT and EVICTED mutually exclusive, and the `reclaimed_count` check distinguishes evicted objects from objects that were never backed. The `atomic_read()` is appropriate here since `panthor_gem_status()` can be called under a spinlock without holding the BO's own lock.

**Debugfs evicted state flag logic:**
```c
if (drm_gem_is_imported(&bo->base))
    gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED;
else if (!resident_size && reclaimed_count)
    gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_EVICTED;

if (bo->base.dma_buf)
    gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED;
```
Note that `EVICTED` and `IMPORTED` are mutually exclusive via `else if`, but `EVICTED` and `EXPORTED` are not (an exported BO that gets evicted would show both flags). Is that the desired behavior? An exported BO could conceivably be evicted, so allowing both flags seems reasonable. But the fdinfo path in `panthor_gem_status()` similarly makes EVICTED exclusive with imported — worth confirming this is intentional for imported buffers (which typically have backing managed by the exporter, so they shouldn't get evicted anyway).

**Minor: `int reclaimed_count` local variable.** The `atomic_read()` returns `int`, so the local is correctly typed. However, the debugfs format uses `%-11d` which handles 10-digit signed ints. Since the value saturates at INT_MAX (~2.1 billion, 10 digits), `%-11d` (10 digits + 1 space) is exactly right.

**No initialization needed** — `panthor_gem_object` is allocated via `kzalloc` (through `drm_gem_shmem_create`), so `reclaimed_count` starts at 0 implicitly. Good.

---
Generated by Claude Code Patch Reviewer

[PATCH v2 3/3] drm/panthor: Reduce padding in gems debugfs for refcount

[Nicolas Frattaroli]

The "gems" debugfs file is getting a little too wide for comfort. While
a lot of this is unavoidable due to the theoretical upper limits of
numbers here (e.g. size needs to be 16 chars because 2**48-1 in decimal
is 15 digits, plus one space for separation), the refcount column has a
decent 5 characters to be saved, as it can only ever contain a 10-digit
decimal number.

Reduce the refcount column's width to 11, which fulfils this requirement
with an additional space for separation.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
---
 drivers/gpu/drm/panthor/panthor_gem.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
index b6fe20b7e6d0..462a9d2ce319 100644
--- a/drivers/gpu/drm/panthor/panthor_gem.c
+++ b/drivers/gpu/drm/panthor/panthor_gem.c
@@ -1644,7 +1644,7 @@ static void panthor_gem_debugfs_bo_print(struct panthor_gem_object *bo,
 
 	snprintf(creator_info, sizeof(creator_info),
 		 "%s/%d", bo->debugfs.creator.process_name, bo->debugfs.creator.tgid);
-	seq_printf(m, "%-32s%-16d%-16d%-11d%-16zd%-16zd0x%-16lx",
+	seq_printf(m, "%-32s%-16d%-11d%-11d%-16zd%-16zd0x%-16lx",
 		   creator_info,
 		   bo->base.name,
 		   refcount,
@@ -1681,8 +1681,8 @@ static void panthor_gem_debugfs_print_bos(struct panthor_device *ptdev,
 
 	panthor_gem_debugfs_print_flag_names(m);
 
-	seq_puts(m, "created-by                      global-name     refcount        evictions  size            resident-size   file-offset       state      usage       label\n");
-	seq_puts(m, "---------------------------------------------------------------------------------------------------------------------------------------------------------\n");
+	seq_puts(m, "created-by                      global-name     refcount   evictions  size            resident-size   file-offset       state      usage       label\n");
+	seq_puts(m, "----------------------------------------------------------------------------------------------------------------------------------------------------\n");
 
 	scoped_guard(mutex, &ptdev->gems.lock) {
 		list_for_each_entry(bo, &ptdev->gems.node, debugfs.node) {
@@ -1690,7 +1690,7 @@ static void panthor_gem_debugfs_print_bos(struct panthor_device *ptdev,
 		}
 	}
 
-	seq_puts(m, "=========================================================================================================================================================\n");
+	seq_puts(m, "====================================================================================================================================================\n");
 	seq_printf(m, "Total size: %zd, Total resident: %zd, Total reclaimable: %zd\n",
 		   totals.size, totals.resident, totals.reclaimable);
 }

-- 
2.53.0

Claude review: drm/panthor: Reduce padding in gems debugfs for refcount

[Claude Code Review Bot]

Patch Review

Trivial cosmetic patch, reducing refcount column width from `%-16d` to `%-11d`.

The commit message correctly notes that `kref` uses `refcount_t` which is an `unsigned int` backed by `atomic_t`, so the maximum value is a 10-digit number. `%-11d` gives 10 digits plus 1 space for separation. This is correct.

**Ordering note:** This patch correctly depends on patch 2 (it modifies lines introduced by patch 2, including the format string and header lines). The interdependency is handled properly.

No issues with this patch.

---
Generated by Claude Code Patch Reviewer

Claude review: Let userspace know about swapped out panthor GEM objects

[Claude Code Review Bot]

Overall Series Review

Subject: Let userspace know about swapped out panthor GEM objects
Author: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Patches: 5
Reviewed: 2026-04-23T08:36:40.531736

---

This is a clean, well-structured 3-patch series that adds eviction observability for panthor GEM objects through both the standardized fdinfo interface and panthor's debugfs. The design is sound: using a saturating atomic counter to distinguish "evicted to swap" from "never yet backed by pages" is the right approach, and the integration with both the core DRM fdinfo framework (patch 1) and panthor's driver-specific debugfs (patch 2) is straightforward.

The main issue is a **missing documentation update**: the new `drm-evicted-<region>` fdinfo key must be documented in `Documentation/gpu/drm-usage-stats.rst`, which defines the standardized userspace-facing interface. Every other memory stat (`total`, `shared`, `resident`, `purgeable`, `active`) is documented there. This is a requirement for any new fdinfo key.

Beyond that, the implementation is correct. The ordering of the atomic increment before page cleanup in the eviction path avoids a race window where an object could appear as neither resident nor evicted. The saturation at `INT_MAX` is appropriate. The core DRM code additions are minimal and consistent with the existing pattern.

---

---
Generated by Claude Code Patch Reviewer

[PATCH 0/2] Let userspace know about swapped out panthor GEM objects

[Nicolas Frattaroli]

Panthor has recently gained a GEM shrinker. It allows evicting memory
that backs unused GEM objects to swap.

In this series, both fdinfo and Panthor's gems debugfs are extended so
that information on evicted pages can be gathered by users through these
two methods.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
---
Nicolas Frattaroli (2):
      drm/fdinfo: Add "evicted" memory accounting
      drm/panthor: Implement evicted status for GEM objects

 drivers/gpu/drm/drm_file.c            |  8 ++++++++
 drivers/gpu/drm/panthor/panthor_gem.c | 10 ++++++++++
 drivers/gpu/drm/panthor/panthor_gem.h | 11 +++++++++++
 include/drm/drm_file.h                |  2 ++
 include/drm/drm_gem.h                 |  2 ++
 5 files changed, 33 insertions(+)
---
base-commit: 3f9357c30a44734d45e3093c521d52b2aefb09f5
change-id: 20260420-panthor-bo-reclaim-observability-970679c9533c

Best regards,
--  
Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

[PATCH 2/2] drm/panthor: Implement evicted status for GEM objects

[Nicolas Frattaroli]

For fdinfo to be able to fill its evicted counter with data, panthor
needs to keep track of whether a GEM object has ever been reclaimed.
Just checking whether the pages are resident isn't enough, as newly
allocated objects also won't be resident.

Do this with a new atomic_t member on panthor_gem_object. It's increased
when an object gets evicted by the shrinker. While it's allowed to wrap
around to below zero and assume a value less than a previous observed
value, the reclaim counter will never return to 0 for any particular
object once it's been reclaimed at least once.

Use this new member to then set the appropriate DRM_GEM_OBJECT_EVICTED
status flag for fdinfo, and use it in the gems debugfs. It's possible to
distinguish evicted non-resident pages from newly allocated non-resident
pages by checking whether reclaimed_count is != 0.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
---
 drivers/gpu/drm/panthor/panthor_gem.c | 10 ++++++++++
 drivers/gpu/drm/panthor/panthor_gem.h | 11 +++++++++++
 2 files changed, 21 insertions(+)

diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
index 69cef05b6ef7..4b761b39565d 100644
--- a/drivers/gpu/drm/panthor/panthor_gem.c
+++ b/drivers/gpu/drm/panthor/panthor_gem.c
@@ -687,6 +687,10 @@ static void panthor_gem_evict_locked(struct panthor_gem_object *bo)
 	if (drm_WARN_ON_ONCE(bo->base.dev, !bo->backing.pages))
 		return;
 
+	/* Don't ever wrap around as far as 0, jump from INT_MIN to 1 */
+	if (!atomic_inc_unless_negative(&bo->reclaimed_count))
+		atomic_set(&bo->reclaimed_count, 1);
+
 	panthor_gem_dev_map_cleanup_locked(bo);
 	panthor_gem_backing_cleanup_locked(bo);
 	panthor_gem_update_reclaim_state_locked(bo, NULL);
@@ -788,6 +792,8 @@ static enum drm_gem_object_status panthor_gem_status(struct drm_gem_object *obj)
 
 	if (drm_gem_is_imported(&bo->base) || bo->backing.pages)
 		res |= DRM_GEM_OBJECT_RESIDENT;
+	else if (atomic_read(&bo->reclaimed_count))
+		res |= DRM_GEM_OBJECT_EVICTED;
 
 	return res;
 }
@@ -1595,6 +1601,7 @@ static void panthor_gem_debugfs_print_flag_names(struct seq_file *m)
 	static const char * const gem_state_flags_names[] = {
 		[PANTHOR_DEBUGFS_GEM_STATE_IMPORTED_BIT] = "imported",
 		[PANTHOR_DEBUGFS_GEM_STATE_EXPORTED_BIT] = "exported",
+		[PANTHOR_DEBUGFS_GEM_STATE_EVICTED_BIT] = "evicted",
 	};
 
 	static const char * const gem_usage_flags_names[] = {
@@ -1648,6 +1655,9 @@ static void panthor_gem_debugfs_bo_print(struct panthor_gem_object *bo,
 
 	if (drm_gem_is_imported(&bo->base))
 		gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED;
+	else if (!resident_size && atomic_read(&bo->reclaimed_count))
+		gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_EVICTED;
+
 	if (bo->base.dma_buf)
 		gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED;
 
diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h
index ae0491d0b121..1ab573f03330 100644
--- a/drivers/gpu/drm/panthor/panthor_gem.h
+++ b/drivers/gpu/drm/panthor/panthor_gem.h
@@ -19,12 +19,16 @@ struct panthor_vm;
 enum panthor_debugfs_gem_state_flags {
 	PANTHOR_DEBUGFS_GEM_STATE_IMPORTED_BIT = 0,
 	PANTHOR_DEBUGFS_GEM_STATE_EXPORTED_BIT = 1,
+	PANTHOR_DEBUGFS_GEM_STATE_EVICTED_BIT = 2,
 
 	/** @PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED: GEM BO is PRIME imported. */
 	PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED = BIT(PANTHOR_DEBUGFS_GEM_STATE_IMPORTED_BIT),
 
 	/** @PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED: GEM BO is PRIME exported. */
 	PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED = BIT(PANTHOR_DEBUGFS_GEM_STATE_EXPORTED_BIT),
+
+	/** @PANTHOR_DEBUGFS_GEM_STATE_FLAG_EVICTED: GEM BO is evicted to swap. */
+	PANTHOR_DEBUGFS_GEM_STATE_FLAG_EVICTED = BIT(PANTHOR_DEBUGFS_GEM_STATE_EVICTED_BIT),
 };
 
 enum panthor_debugfs_gem_usage_flags {
@@ -172,6 +176,13 @@ struct panthor_gem_object {
 	/** @reclaim_state: Cached reclaim state */
 	enum panthor_gem_reclaim_state reclaim_state;
 
+	/**
+	 * @reclaimed_count: How many times object has been evicted to swap.
+	 * Never returns to 0 once incremented even on wrap-around, but may
+	 * become < 0 and < the previous value if wrap-around occurs.
+	 */
+	atomic_t reclaimed_count;
+
 	/**
 	 * @exclusive_vm_root_gem: Root GEM of the exclusive VM this GEM object
 	 * is attached to.

-- 
2.53.0

Claude review: drm/panthor: Implement evicted status for GEM objects

[Claude Code Review Bot]

Patch Review

**Summary:** Adds an `atomic_t reclaimed_count` field to `panthor_gem_object`, increments it in the evict path, and uses it to report `DRM_GEM_OBJECT_EVICTED` via the `.status` callback and the debugfs gems interface.

**Review:**

**Issue 1 (design): The wrap-around avoidance is over-engineered for a boolean need.**

```c
	/* Don't ever wrap around as far as 0, jump from INT_MIN to 1 */
	if (!atomic_inc_unless_negative(&bo->reclaimed_count))
		atomic_set(&bo->reclaimed_count, 1);
```

The only consumer of `reclaimed_count` checks `!= 0`:
```c
	else if (atomic_read(&bo->reclaimed_count))
		res |= DRM_GEM_OBJECT_EVICTED;
```

If the sole purpose is "has this BO ever been evicted", a simple `bool` or even a flag bit would suffice. The commit message justifies the counter by saying "It's possible to distinguish evicted non-resident pages from newly allocated non-resident pages by checking whether reclaimed_count is != 0" — but that's the same as a boolean.

If there's a genuine use case for knowing *how many times* a BO was evicted (e.g., for future debugfs stats), the counter makes sense. But in that case, the wrap-around logic is wrong — after wrap-around, the count is no longer meaningful. And `atomic_inc_unless_negative` is not a cheap operation (it's a cmpxchg loop), unlike a simple `atomic_inc` or `atomic_set`.

Suggestion: Either use a simpler `bool evicted` (or a flag bit) if you only need the boolean, or use a plain `atomic_inc` if you want a counter (wrap-around after 2^31 evictions is not a real-world concern, and the count being "wrong" after wrap is no worse than clamping at 1).

**Issue 2 (atomics concern): `atomic_set` after failed `atomic_inc_unless_negative` is not atomic with respect to concurrent reads.**

```c
	if (!atomic_inc_unless_negative(&bo->reclaimed_count))
		atomic_set(&bo->reclaimed_count, 1);
```

If two threads hit this simultaneously when `reclaimed_count` is `INT_MIN`, both could see `atomic_inc_unless_negative` fail (since `INT_MIN` is negative), and both call `atomic_set(&bo->reclaimed_count, 1)`. That's fine — the result is still 1. But there's a window where a concurrent `atomic_read` from `panthor_gem_status` could observe 0 if the set hasn't completed. In practice, this is harmless since:
- Eviction holds a lock (`panthor_gem_evict_locked`)
- The status read is racy by design (documented in `drm_gem_object_funcs.status`)

But it would be cleaner to just use `atomic_inc` and accept that the counter can wrap, or use a simple flag.

**Issue 3 (logic): The `else if` chain in `panthor_gem_status` means imported objects can never be reported as evicted.**

```c
	if (drm_gem_is_imported(&bo->base) || bo->backing.pages)
		res |= DRM_GEM_OBJECT_RESIDENT;
	else if (atomic_read(&bo->reclaimed_count))
		res |= DRM_GEM_OBJECT_EVICTED;
```

Since imported objects always get `RESIDENT`, they can never get `EVICTED`. This is probably correct (imported objects shouldn't be evicted by the panthor shrinker), but worth confirming — does the panthor shrinker skip imported BOs? If an imported BO were somehow evicted, the status would incorrectly show it as `RESIDENT`.

**Issue 4 (debugfs): Same `else if` pattern with different condition for debugfs.**

```c
	if (drm_gem_is_imported(&bo->base))
		gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED;
	else if (!resident_size && atomic_read(&bo->reclaimed_count))
		gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_EVICTED;

	if (bo->base.dma_buf)
		gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED;
```

Note the `else if` means an imported BO will never show as evicted in debugfs either. An exported BO *can* show as evicted (since the exported check uses a separate `if`), which is inconsistent with the imported BO treatment. If an exported BO is evicted, it will show both "exported" and "evicted" flags in debugfs, which seems correct. But an imported+evicted BO (if possible) would only show "imported". This is a minor consistency concern.

**Issue 5 (missing initialization): `reclaimed_count` is not explicitly initialized.**

The new `atomic_t reclaimed_count` field in `panthor_gem_object` is not explicitly initialized to 0 in any allocation path. This relies on the GEM object being allocated with `kzalloc` (via shmem helpers), which zero-initializes the entire struct. This works correctly for `atomic_t` since `ATOMIC_INIT(0)` is just `{ 0 }`, but it's worth noting that this is an implicit dependency on zero-initialization.

**Issue 6 (nit): Comment style.**

```c
	/* Don't ever wrap around as far as 0, jump from INT_MIN to 1 */
```

This is a reasonable comment given the non-obvious wrap-around handling, though it could be simplified if the approach itself is simplified.

**Positive aspects:**
- The debugfs flag naming table is correctly extended
- The `else if` logic in `panthor_gem_status` correctly makes `EVICTED` mutually exclusive with `RESIDENT`
- The commit message is well-written and clearly explains the rationale

---

**Summary:** The series is architecturally sound and fills a real observability gap. The main feedback is: (1) consider whether `obj->size` is more appropriate than `add_size` for the evicted counter in patch 1, (2) simplify the `reclaimed_count` to either a plain boolean flag or a simple `atomic_inc` counter in patch 2, and (3) add documentation about `EVICTED`/`RESIDENT` mutual exclusivity to the enum comments.

---
Generated by Claude Code Patch Reviewer