[RFC,1/5] mm: add MM_DRIVERPAGES

Commit Message

Lucas Stach Sept. 9, 2022, 11:16 a.m. UTC

This adds a mm counter for pages allocated by a driver on behalf of
a userspace task.

Especially with DRM drivers there can be large amounts of pages that
are never mapped into userspace and thus are not tracked by the usual
ANONPAGES mmap accounting, as those pages are only ever touched by the
device. They can make up a significant portion of the tasks resident
memory size, but are currently not visible in any of the memory
statistics visible to userspace and the OOM handling.

Add the counter to allow tracking such memory, which allows to make
more sensible decisions in the OOM handling as well as allowing
userspace some better insight into the real system memory usage.

Signed-off-by: Lucas Stach <[e-mail]>
---
 fs/proc/task_mmu.c            | 6 ++++--
 include/linux/mm.h            | 3 ++-
 include/linux/mm_types_task.h | 1 +
 kernel/fork.c                 | 1 +
 4 files changed, 8 insertions(+), 3 deletions(-)

Patch

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index a3398d0f1927..80b095a233bf 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -33,7 +33,8 @@  void task_mem(struct seq_file *m, struct mm_struct *mm)
 	unsigned long text, lib, swap, anon, file, shmem;
 	unsigned long hiwater_vm, total_vm, hiwater_rss, total_rss;
 
-	anon = get_mm_counter(mm, MM_ANONPAGES);
+	anon = get_mm_counter(mm, MM_ANONPAGES) +
+	       get_mm_counter(mm, MM_DRIVERPAGES);
 	file = get_mm_counter(mm, MM_FILEPAGES);
 	shmem = get_mm_counter(mm, MM_SHMEMPAGES);
 
@@ -94,7 +95,8 @@  unsigned long task_statm(struct mm_struct *mm,
 	*text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK))
 								>> PAGE_SHIFT;
 	*data = mm->data_vm + mm->stack_vm;
-	*resident = *shared + get_mm_counter(mm, MM_ANONPAGES);
+	*resident = *shared + get_mm_counter(mm, MM_ANONPAGES) +
+		    get_mm_counter(mm, MM_DRIVERPAGES);
 	return mm->total_vm;
 }
 
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3bedc449c14d..2cc014d1ea27 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2003,7 +2003,8 @@  static inline unsigned long get_mm_rss(struct mm_struct *mm)
 {
 	return get_mm_counter(mm, MM_FILEPAGES) +
 		get_mm_counter(mm, MM_ANONPAGES) +
-		get_mm_counter(mm, MM_SHMEMPAGES);
+		get_mm_counter(mm, MM_SHMEMPAGES) +
+		get_mm_counter(mm, MM_DRIVERPAGES);
 }
 
 static inline unsigned long get_mm_hiwater_rss(struct mm_struct *mm)
diff --git a/include/linux/mm_types_task.h b/include/linux/mm_types_task.h
index c1bc6731125c..420d88e79906 100644
--- a/include/linux/mm_types_task.h
+++ b/include/linux/mm_types_task.h
@@ -45,6 +45,7 @@  enum {
 	MM_ANONPAGES,	/* Resident anonymous pages */
 	MM_SWAPENTS,	/* Anonymous swap entries */
 	MM_SHMEMPAGES,	/* Resident shared memory pages */
+	MM_DRIVERPAGES,	/* pages allocated by a driver on behalf of a task */
 	NR_MM_COUNTERS
 };
 
diff --git a/kernel/fork.c b/kernel/fork.c
index 90c85b17bf69..74a07a2288ba 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -135,6 +135,7 @@  static const char * const resident_page_types[] = {
 	NAMED_ARRAY_INDEX(MM_ANONPAGES),
 	NAMED_ARRAY_INDEX(MM_SWAPENTS),
 	NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
+	NAMED_ARRAY_INDEX(MM_DRIVERPAGES),
 };
 
 DEFINE_PER_CPU(unsigned long, process_counts) = 0;