drm/panthor: Implement evicted status for GEM objects

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

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.

Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Link: https://patch.msgid.link/20260521-panthor-bo-reclaim-observability-v5-1-49313994da55@collabora.com
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
index abe0c5bb1bca3b9ff35413a25cac68eba39c255f..ec2abc6ce417d66dce6901e403aa328111befc5d 100644 (file)
--- 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);
@@ -1590,6 +1592,7 @@ 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[] = {
@@ -1620,6 +1623,7 @@ 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;
@@ -1633,16 +1637,20 @@ 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;
 
@@ -1666,8 +1674,8 @@ 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) {
@@ -1675,7 +1683,7 @@ 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 ae0491d0b12161f9d87341de8bdf680885e63805..56d63137b4ebbf0833f32e1e32a9c42664b736dd 100644 (file)
--- 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.