[PATCH v6] mm, drm/i915: mark pinned shmemfs pages as unevictable

[PATCH v6] mm, drm/i915: mark pinned shmemfs pages as unevictable

[Kuo-Hsin Yang]

The i915 driver uses shmemfs to allocate backing storage for gem
objects. These shmemfs pages can be pinned (increased ref count) by
shmem_read_mapping_page_gfp(). When a lot of pages are pinned, vmscan
wastes a lot of time scanning these pinned pages. In some extreme case,
all pages in the inactive anon lru are pinned, and only the inactive
anon lru is scanned due to inactive_ratio, the system cannot swap and
invokes the oom-killer. Mark these pinned pages as unevictable to speed
up vmscan.

Export pagevec API check_move_unevictable_pages().

This patch was inspired by Chris Wilson's change [1].

[1]: https://patchwork.kernel.org/patch/9768741/

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Kuo-Hsin Yang <vovoy@chromium.org>
Acked-by: Michal Hocko <mhocko@suse.com> # mm part
---
Changes for v6:
 Tweak the acked-by.

Changes for v5:
 Modify doc and comments. Remove the ifdef surrounding
 check_move_unevictable_pages.

Changes for v4:
 Export pagevec API check_move_unevictable_pages().

Changes for v3:
 Use check_move_lru_page instead of shmem_unlock_mapping to move pages
 to appropriate lru lists.

Changes for v2:
 Squashed the two patches.

 Documentation/vm/unevictable-lru.rst |  6 +++++-
 drivers/gpu/drm/i915/i915_gem.c      | 28 ++++++++++++++++++++++++++--
 include/linux/swap.h                 |  4 +++-
 mm/shmem.c                           |  2 +-
 mm/vmscan.c                          | 22 +++++++++++-----------
 5 files changed, 46 insertions(+), 16 deletions(-)

diff --git a/Documentation/vm/unevictable-lru.rst b/Documentation/vm/unevictable-lru.rst
index fdd84cb8d511..b8e29f977f2d 100644
--- a/Documentation/vm/unevictable-lru.rst
+++ b/Documentation/vm/unevictable-lru.rst
@@ -143,7 +143,7 @@ using a number of wrapper functions:
 	Query the address space, and return true if it is completely
 	unevictable.
 
-These are currently used in two places in the kernel:
+These are currently used in three places in the kernel:
 
  (1) By ramfs to mark the address spaces of its inodes when they are created,
      and this mark remains for the life of the inode.
@@ -154,6 +154,10 @@ These are currently used in two places in the kernel:
      swapped out; the application must touch the pages manually if it wants to
      ensure they're in memory.
 
+ (3) By the i915 driver to mark pinned address space until it's unpinned. The
+     amount of unevictable memory marked by i915 driver is roughly the bounded
+     object size in debugfs/dri/0/i915_gem_objects.
+
 
 Detecting Unevictable Pages
 ---------------------------
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 0c8aa57ce83b..c620891e0d02 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2381,12 +2381,25 @@ void __i915_gem_object_invalidate(struct drm_i915_gem_object *obj)
 	invalidate_mapping_pages(mapping, 0, (loff_t)-1);
 }
 
+/**
+ * Move pages to appropriate lru and release the pagevec. Decrement the ref
+ * count of these pages.
+ */
+static inline void check_release_pagevec(struct pagevec *pvec)
+{
+	if (pagevec_count(pvec)) {
+		check_move_unevictable_pages(pvec);
+		__pagevec_release(pvec);
+	}
+}
+
 static void
 i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj,
 			      struct sg_table *pages)
 {
 	struct sgt_iter sgt_iter;
 	struct page *page;
+	struct pagevec pvec;
 
 	__i915_gem_object_release_shmem(obj, pages, true);
 
@@ -2395,6 +2408,9 @@ i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj,
 	if (i915_gem_object_needs_bit17_swizzle(obj))
 		i915_gem_object_save_bit_17_swizzle(obj, pages);
 
+	mapping_clear_unevictable(file_inode(obj->base.filp)->i_mapping);
+
+	pagevec_init(&pvec);
 	for_each_sgt_page(page, sgt_iter, pages) {
 		if (obj->mm.dirty)
 			set_page_dirty(page);
@@ -2402,8 +2418,10 @@ i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj,
 		if (obj->mm.madv == I915_MADV_WILLNEED)
 			mark_page_accessed(page);
 
-		put_page(page);
+		if (!pagevec_add(&pvec, page))
+			check_release_pagevec(&pvec);
 	}
+	check_release_pagevec(&pvec);
 	obj->mm.dirty = false;
 
 	sg_free_table(pages);
@@ -2526,6 +2544,7 @@ static int i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 	unsigned int sg_page_sizes;
 	gfp_t noreclaim;
 	int ret;
+	struct pagevec pvec;
 
 	/*
 	 * Assert that the object is not currently in any GPU domain. As it
@@ -2559,6 +2578,7 @@ static int i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 	 * Fail silently without starting the shrinker
 	 */
 	mapping = obj->base.filp->f_mapping;
+	mapping_set_unevictable(mapping);
 	noreclaim = mapping_gfp_constraint(mapping, ~__GFP_RECLAIM);
 	noreclaim |= __GFP_NORETRY | __GFP_NOWARN;
 
@@ -2673,8 +2693,12 @@ static int i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 err_sg:
 	sg_mark_end(sg);
 err_pages:
+	mapping_clear_unevictable(mapping);
+	pagevec_init(&pvec);
 	for_each_sgt_page(page, sgt_iter, st)
-		put_page(page);
+		if (!pagevec_add(&pvec, page))
+			check_release_pagevec(&pvec);
+	check_release_pagevec(&pvec);
 	sg_free_table(st);
 	kfree(st);
 
diff --git a/include/linux/swap.h b/include/linux/swap.h
index d8a07a4f171d..a8f6d5d89524 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -18,6 +18,8 @@ struct notifier_block;
 
 struct bio;
 
+struct pagevec;
+
 #define SWAP_FLAG_PREFER	0x8000	/* set if swap priority specified */
 #define SWAP_FLAG_PRIO_MASK	0x7fff
 #define SWAP_FLAG_PRIO_SHIFT	0
@@ -369,7 +371,7 @@ static inline int node_reclaim(struct pglist_data *pgdat, gfp_t mask,
 #endif
 
 extern int page_evictable(struct page *page);
-extern void check_move_unevictable_pages(struct page **, int nr_pages);
+extern void check_move_unevictable_pages(struct pagevec *pvec);
 
 extern int kswapd_run(int nid);
 extern void kswapd_stop(int nid);
diff --git a/mm/shmem.c b/mm/shmem.c
index ea26d7a0342d..de4893c904a3 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -756,7 +756,7 @@ void shmem_unlock_mapping(struct address_space *mapping)
 			break;
 		index = indices[pvec.nr - 1] + 1;
 		pagevec_remove_exceptionals(&pvec);
-		check_move_unevictable_pages(pvec.pages, pvec.nr);
+		check_move_unevictable_pages(&pvec);
 		pagevec_release(&pvec);
 		cond_resched();
 	}
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 62ac0c488624..d070f431ff19 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -50,6 +50,7 @@
 #include <linux/printk.h>
 #include <linux/dax.h>
 #include <linux/psi.h>
+#include <linux/pagevec.h>
 
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
@@ -4182,17 +4183,16 @@ int page_evictable(struct page *page)
 	return ret;
 }
 
-#ifdef CONFIG_SHMEM
 /**
- * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
- * @pages:	array of pages to check
- * @nr_pages:	number of pages to check
+ * check_move_unevictable_pages - check pages for evictability and move to
+ * appropriate zone lru list
+ * @pvec: pagevec with lru pages to check
  *
- * Checks pages for evictability and moves them to the appropriate lru list.
- *
- * This function is only used for SysV IPC SHM_UNLOCK.
+ * Checks pages for evictability, if an evictable page is in the unevictable
+ * lru list, moves it to the appropriate evictable lru list. This function
+ * should be only used for lru pages.
  */
-void check_move_unevictable_pages(struct page **pages, int nr_pages)
+void check_move_unevictable_pages(struct pagevec *pvec)
 {
 	struct lruvec *lruvec;
 	struct pglist_data *pgdat = NULL;
@@ -4200,8 +4200,8 @@ void check_move_unevictable_pages(struct page **pages, int nr_pages)
 	int pgrescued = 0;
 	int i;
 
-	for (i = 0; i < nr_pages; i++) {
-		struct page *page = pages[i];
+	for (i = 0; i < pvec->nr; i++) {
+		struct page *page = pvec->pages[i];
 		struct pglist_data *pagepgdat = page_pgdat(page);
 
 		pgscanned++;
@@ -4233,4 +4233,4 @@ void check_move_unevictable_pages(struct page **pages, int nr_pages)
 		spin_unlock_irq(&pgdat->lru_lock);
 	}
 }
-#endif /* CONFIG_SHMEM */
+EXPORT_SYMBOL_GPL(check_move_unevictable_pages);
-- 
2.19.1.930.g4563a0d9d0-goog

Re: [PATCH v6] mm, drm/i915: mark pinned shmemfs pages as unevictable

[Daniel Vetter]

On Tue, Nov 06, 2018 at 05:30:59PM +0800, Kuo-Hsin Yang wrote:
> The i915 driver uses shmemfs to allocate backing storage for gem
> objects. These shmemfs pages can be pinned (increased ref count) by
> shmem_read_mapping_page_gfp(). When a lot of pages are pinned, vmscan
> wastes a lot of time scanning these pinned pages. In some extreme case,
> all pages in the inactive anon lru are pinned, and only the inactive
> anon lru is scanned due to inactive_ratio, the system cannot swap and
> invokes the oom-killer. Mark these pinned pages as unevictable to speed
> up vmscan.
> 
> Export pagevec API check_move_unevictable_pages().
> 
> This patch was inspired by Chris Wilson's change [1].
> 
> [1]: https://patchwork.kernel.org/patch/9768741/
> 
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Signed-off-by: Kuo-Hsin Yang <vovoy@chromium.org>
> Acked-by: Michal Hocko <mhocko@suse.com> # mm part

There was ages ago some planes to have our own i915fs, so that we could
overwrite the address_space hooks for page migration and eviction and that
sort of thing, which would make all these pages evictable. Atm you have to
ĥope our shrinker drops them on the floor, which I think is fairly
confusing to core mm code (it's kinda like page eviction worked way back
before rmaps).

Just an side really.
-Daniel

> ---
> Changes for v6:
>  Tweak the acked-by.
> 
> Changes for v5:
>  Modify doc and comments. Remove the ifdef surrounding
>  check_move_unevictable_pages.
> 
> Changes for v4:
>  Export pagevec API check_move_unevictable_pages().
> 
> Changes for v3:
>  Use check_move_lru_page instead of shmem_unlock_mapping to move pages
>  to appropriate lru lists.
> 
> Changes for v2:
>  Squashed the two patches.
> 
>  Documentation/vm/unevictable-lru.rst |  6 +++++-
>  drivers/gpu/drm/i915/i915_gem.c      | 28 ++++++++++++++++++++++++++--
>  include/linux/swap.h                 |  4 +++-
>  mm/shmem.c                           |  2 +-
>  mm/vmscan.c                          | 22 +++++++++++-----------
>  5 files changed, 46 insertions(+), 16 deletions(-)
> 
> diff --git a/Documentation/vm/unevictable-lru.rst b/Documentation/vm/unevictable-lru.rst
> index fdd84cb8d511..b8e29f977f2d 100644
> --- a/Documentation/vm/unevictable-lru.rst
> +++ b/Documentation/vm/unevictable-lru.rst
> @@ -143,7 +143,7 @@ using a number of wrapper functions:
>  	Query the address space, and return true if it is completely
>  	unevictable.
>  
> -These are currently used in two places in the kernel:
> +These are currently used in three places in the kernel:
>  
>   (1) By ramfs to mark the address spaces of its inodes when they are created,
>       and this mark remains for the life of the inode.
> @@ -154,6 +154,10 @@ These are currently used in two places in the kernel:
>       swapped out; the application must touch the pages manually if it wants to
>       ensure they're in memory.
>  
> + (3) By the i915 driver to mark pinned address space until it's unpinned. The
> +     amount of unevictable memory marked by i915 driver is roughly the bounded
> +     object size in debugfs/dri/0/i915_gem_objects.
> +
>  
>  Detecting Unevictable Pages
>  ---------------------------
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 0c8aa57ce83b..c620891e0d02 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2381,12 +2381,25 @@ void __i915_gem_object_invalidate(struct drm_i915_gem_object *obj)
>  	invalidate_mapping_pages(mapping, 0, (loff_t)-1);
>  }
>  
> +/**
> + * Move pages to appropriate lru and release the pagevec. Decrement the ref
> + * count of these pages.
> + */
> +static inline void check_release_pagevec(struct pagevec *pvec)
> +{
> +	if (pagevec_count(pvec)) {
> +		check_move_unevictable_pages(pvec);
> +		__pagevec_release(pvec);
> +	}
> +}
> +
>  static void
>  i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj,
>  			      struct sg_table *pages)
>  {
>  	struct sgt_iter sgt_iter;
>  	struct page *page;
> +	struct pagevec pvec;
>  
>  	__i915_gem_object_release_shmem(obj, pages, true);
>  
> @@ -2395,6 +2408,9 @@ i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj,
>  	if (i915_gem_object_needs_bit17_swizzle(obj))
>  		i915_gem_object_save_bit_17_swizzle(obj, pages);
>  
> +	mapping_clear_unevictable(file_inode(obj->base.filp)->i_mapping);
> +
> +	pagevec_init(&pvec);
>  	for_each_sgt_page(page, sgt_iter, pages) {
>  		if (obj->mm.dirty)
>  			set_page_dirty(page);
> @@ -2402,8 +2418,10 @@ i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj,
>  		if (obj->mm.madv == I915_MADV_WILLNEED)
>  			mark_page_accessed(page);
>  
> -		put_page(page);
> +		if (!pagevec_add(&pvec, page))
> +			check_release_pagevec(&pvec);
>  	}
> +	check_release_pagevec(&pvec);
>  	obj->mm.dirty = false;
>  
>  	sg_free_table(pages);
> @@ -2526,6 +2544,7 @@ static int i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
>  	unsigned int sg_page_sizes;
>  	gfp_t noreclaim;
>  	int ret;
> +	struct pagevec pvec;
>  
>  	/*
>  	 * Assert that the object is not currently in any GPU domain. As it
> @@ -2559,6 +2578,7 @@ static int i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
>  	 * Fail silently without starting the shrinker
>  	 */
>  	mapping = obj->base.filp->f_mapping;
> +	mapping_set_unevictable(mapping);
>  	noreclaim = mapping_gfp_constraint(mapping, ~__GFP_RECLAIM);
>  	noreclaim |= __GFP_NORETRY | __GFP_NOWARN;
>  
> @@ -2673,8 +2693,12 @@ static int i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
>  err_sg:
>  	sg_mark_end(sg);
>  err_pages:
> +	mapping_clear_unevictable(mapping);
> +	pagevec_init(&pvec);
>  	for_each_sgt_page(page, sgt_iter, st)
> -		put_page(page);
> +		if (!pagevec_add(&pvec, page))
> +			check_release_pagevec(&pvec);
> +	check_release_pagevec(&pvec);
>  	sg_free_table(st);
>  	kfree(st);
>  
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index d8a07a4f171d..a8f6d5d89524 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -18,6 +18,8 @@ struct notifier_block;
>  
>  struct bio;
>  
> +struct pagevec;
> +
>  #define SWAP_FLAG_PREFER	0x8000	/* set if swap priority specified */
>  #define SWAP_FLAG_PRIO_MASK	0x7fff
>  #define SWAP_FLAG_PRIO_SHIFT	0
> @@ -369,7 +371,7 @@ static inline int node_reclaim(struct pglist_data *pgdat, gfp_t mask,
>  #endif
>  
>  extern int page_evictable(struct page *page);
> -extern void check_move_unevictable_pages(struct page **, int nr_pages);
> +extern void check_move_unevictable_pages(struct pagevec *pvec);
>  
>  extern int kswapd_run(int nid);
>  extern void kswapd_stop(int nid);
> diff --git a/mm/shmem.c b/mm/shmem.c
> index ea26d7a0342d..de4893c904a3 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -756,7 +756,7 @@ void shmem_unlock_mapping(struct address_space *mapping)
>  			break;
>  		index = indices[pvec.nr - 1] + 1;
>  		pagevec_remove_exceptionals(&pvec);
> -		check_move_unevictable_pages(pvec.pages, pvec.nr);
> +		check_move_unevictable_pages(&pvec);
>  		pagevec_release(&pvec);
>  		cond_resched();
>  	}
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 62ac0c488624..d070f431ff19 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -50,6 +50,7 @@
>  #include <linux/printk.h>
>  #include <linux/dax.h>
>  #include <linux/psi.h>
> +#include <linux/pagevec.h>
>  
>  #include <asm/tlbflush.h>
>  #include <asm/div64.h>
> @@ -4182,17 +4183,16 @@ int page_evictable(struct page *page)
>  	return ret;
>  }
>  
> -#ifdef CONFIG_SHMEM
>  /**
> - * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
> - * @pages:	array of pages to check
> - * @nr_pages:	number of pages to check
> + * check_move_unevictable_pages - check pages for evictability and move to
> + * appropriate zone lru list
> + * @pvec: pagevec with lru pages to check
>   *
> - * Checks pages for evictability and moves them to the appropriate lru list.
> - *
> - * This function is only used for SysV IPC SHM_UNLOCK.
> + * Checks pages for evictability, if an evictable page is in the unevictable
> + * lru list, moves it to the appropriate evictable lru list. This function
> + * should be only used for lru pages.
>   */
> -void check_move_unevictable_pages(struct page **pages, int nr_pages)
> +void check_move_unevictable_pages(struct pagevec *pvec)
>  {
>  	struct lruvec *lruvec;
>  	struct pglist_data *pgdat = NULL;
> @@ -4200,8 +4200,8 @@ void check_move_unevictable_pages(struct page **pages, int nr_pages)
>  	int pgrescued = 0;
>  	int i;
>  
> -	for (i = 0; i < nr_pages; i++) {
> -		struct page *page = pages[i];
> +	for (i = 0; i < pvec->nr; i++) {
> +		struct page *page = pvec->pages[i];
>  		struct pglist_data *pagepgdat = page_pgdat(page);
>  
>  		pgscanned++;
> @@ -4233,4 +4233,4 @@ void check_move_unevictable_pages(struct page **pages, int nr_pages)
>  		spin_unlock_irq(&pgdat->lru_lock);
>  	}
>  }
> -#endif /* CONFIG_SHMEM */
> +EXPORT_SYMBOL_GPL(check_move_unevictable_pages);
> -- 
> 2.19.1.930.g4563a0d9d0-goog
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH v6] mm, drm/i915: mark pinned shmemfs pages as unevictable

[Chris Wilson]

Quoting Kuo-Hsin Yang (2018-11-06 09:30:59)
> The i915 driver uses shmemfs to allocate backing storage for gem
> objects. These shmemfs pages can be pinned (increased ref count) by
> shmem_read_mapping_page_gfp(). When a lot of pages are pinned, vmscan
> wastes a lot of time scanning these pinned pages. In some extreme case,
> all pages in the inactive anon lru are pinned, and only the inactive
> anon lru is scanned due to inactive_ratio, the system cannot swap and
> invokes the oom-killer. Mark these pinned pages as unevictable to speed
> up vmscan.
> 
> Export pagevec API check_move_unevictable_pages().
> 
> This patch was inspired by Chris Wilson's change [1].
> 
> [1]: https://patchwork.kernel.org/patch/9768741/
> 
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Signed-off-by: Kuo-Hsin Yang <vovoy@chromium.org>
> Acked-by: Michal Hocko <mhocko@suse.com> # mm part
> ---
> Changes for v6:
>  Tweak the acked-by.
> 
> Changes for v5:
>  Modify doc and comments. Remove the ifdef surrounding
>  check_move_unevictable_pages.
> 
> Changes for v4:
>  Export pagevec API check_move_unevictable_pages().
> 
> Changes for v3:
>  Use check_move_lru_page instead of shmem_unlock_mapping to move pages
>  to appropriate lru lists.
> 
> Changes for v2:
>  Squashed the two patches.
> 
>  Documentation/vm/unevictable-lru.rst |  6 +++++-
>  drivers/gpu/drm/i915/i915_gem.c      | 28 ++++++++++++++++++++++++++--
>  include/linux/swap.h                 |  4 +++-
>  mm/shmem.c                           |  2 +-
>  mm/vmscan.c                          | 22 +++++++++++-----------
>  5 files changed, 46 insertions(+), 16 deletions(-)
> 
> diff --git a/Documentation/vm/unevictable-lru.rst b/Documentation/vm/unevictable-lru.rst
> index fdd84cb8d511..b8e29f977f2d 100644
> --- a/Documentation/vm/unevictable-lru.rst
> +++ b/Documentation/vm/unevictable-lru.rst
> @@ -143,7 +143,7 @@ using a number of wrapper functions:
>         Query the address space, and return true if it is completely
>         unevictable.
>  
> -These are currently used in two places in the kernel:
> +These are currently used in three places in the kernel:
>  
>   (1) By ramfs to mark the address spaces of its inodes when they are created,
>       and this mark remains for the life of the inode.
> @@ -154,6 +154,10 @@ These are currently used in two places in the kernel:
>       swapped out; the application must touch the pages manually if it wants to
>       ensure they're in memory.
>  
> + (3) By the i915 driver to mark pinned address space until it's unpinned. The
> +     amount of unevictable memory marked by i915 driver is roughly the bounded
> +     object size in debugfs/dri/0/i915_gem_objects.
> +
>  
>  Detecting Unevictable Pages
>  ---------------------------
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 0c8aa57ce83b..c620891e0d02 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2381,12 +2381,25 @@ void __i915_gem_object_invalidate(struct drm_i915_gem_object *obj)
>         invalidate_mapping_pages(mapping, 0, (loff_t)-1);
>  }
>  
> +/**
> + * Move pages to appropriate lru and release the pagevec. Decrement the ref
> + * count of these pages.
> + */
> +static inline void check_release_pagevec(struct pagevec *pvec)
> +{
> +       if (pagevec_count(pvec)) {
> +               check_move_unevictable_pages(pvec);
> +               __pagevec_release(pvec);

This gave disappointing syslatency results until I put a cond_resched()
here and moved the one in put_pages_gtt to before the page alloc, see
https://patchwork.freedesktop.org/patch/260332/

The last really nasty wart for syslatency is the spin in
i915_gem_shrinker, for which I'm investigating
https://patchwork.freedesktop.org/patch/260365/

All 3 patches together give very reasonable syslatency results! (So
good that it's time to find a new worst case scenario!)

The challenge for the patch as it stands, is who lands it? We can take
it through drm-intel (for merging in 4.21) but need Andrew's ack on top
of all to agree with that path. Or we split the patch and only land the
i915 portion once we backmerge the mm tree. I think pushing the i915
portion through the mm tree is going to cause the most conflicts, so
would recommend against that.
-Chris

Re: [PATCH v6] mm, drm/i915: mark pinned shmemfs pages as unevictable

[Kuo-Hsin Yang]

On Tue, Nov 6, 2018 at 7:07 PM Chris Wilson <chris@chris-wilson.co.uk> wrote:
> This gave disappointing syslatency results until I put a cond_resched()
> here and moved the one in put_pages_gtt to before the page alloc, see
> https://patchwork.freedesktop.org/patch/260332/
>
> The last really nasty wart for syslatency is the spin in
> i915_gem_shrinker, for which I'm investigating
> https://patchwork.freedesktop.org/patch/260365/
>
> All 3 patches together give very reasonable syslatency results! (So
> good that it's time to find a new worst case scenario!)
>
> The challenge for the patch as it stands, is who lands it? We can take
> it through drm-intel (for merging in 4.21) but need Andrew's ack on top
> of all to agree with that path. Or we split the patch and only land the
> i915 portion once we backmerge the mm tree. I think pushing the i915
> portion through the mm tree is going to cause the most conflicts, so
> would recommend against that.

Splitting the patch and landing the mm part first sounds reasonable to me.

Re: [PATCH v6] mm, drm/i915: mark pinned shmemfs pages as unevictable

[Michal Hocko]

On Tue 06-11-18 11:06:58, Chris Wilson wrote:
[...]
> The challenge for the patch as it stands, is who lands it? We can take
> it through drm-intel (for merging in 4.21) but need Andrew's ack on top
> of all to agree with that path. Or we split the patch and only land the
> i915 portion once we backmerge the mm tree. I think pushing the i915
> portion through the mm tree is going to cause the most conflicts, so
> would recommend against that.

I usually prefer new exports to go along with their users. I am pretty
sure that the core mm change can be routed via whatever tree needs that.
Up to Andrew but this doesn't seem to be conflicting with anything that
is going on in MM.
-- 
Michal Hocko
SUSE Labs

[PATCH v7] mm, drm/i915: mark pinned shmemfs pages as unevictable

[Chris Wilson]

From: Kuo-Hsin Yang <vovoy@chromium.org>

The i915 driver uses shmemfs to allocate backing storage for gem
objects. These shmemfs pages can be pinned (increased ref count) by
shmem_read_mapping_page_gfp(). When a lot of pages are pinned, vmscan
wastes a lot of time scanning these pinned pages. In some extreme case,
all pages in the inactive anon lru are pinned, and only the inactive
anon lru is scanned due to inactive_ratio, the system cannot swap and
invokes the oom-killer. Mark these pinned pages as unevictable to speed
up vmscan.

Export pagevec API check_move_unevictable_pages().

This patch was inspired by Chris Wilson's change [1].

[1]: https://patchwork.kernel.org/patch/9768741/

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Kuo-Hsin Yang <vovoy@chromium.org>
Acked-by: Michal Hocko <mhocko@suse.com> # mm part
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
---
Rebased on drm-intel-next-queued to pick up a cond_resched()
-Chris
---
 Documentation/vm/unevictable-lru.rst |  6 +++++-
 drivers/gpu/drm/i915/i915_gem.c      | 30 +++++++++++++++++++++++++---
 include/linux/swap.h                 |  4 +++-
 mm/shmem.c                           |  2 +-
 mm/vmscan.c                          | 22 ++++++++++----------
 5 files changed, 47 insertions(+), 17 deletions(-)

diff --git a/Documentation/vm/unevictable-lru.rst b/Documentation/vm/unevictable-lru.rst
index fdd84cb8d511..b8e29f977f2d 100644
--- a/Documentation/vm/unevictable-lru.rst
+++ b/Documentation/vm/unevictable-lru.rst
@@ -143,7 +143,7 @@ using a number of wrapper functions:
 	Query the address space, and return true if it is completely
 	unevictable.
 
-These are currently used in two places in the kernel:
+These are currently used in three places in the kernel:
 
  (1) By ramfs to mark the address spaces of its inodes when they are created,
      and this mark remains for the life of the inode.
@@ -154,6 +154,10 @@ These are currently used in two places in the kernel:
      swapped out; the application must touch the pages manually if it wants to
      ensure they're in memory.
 
+ (3) By the i915 driver to mark pinned address space until it's unpinned. The
+     amount of unevictable memory marked by i915 driver is roughly the bounded
+     object size in debugfs/dri/0/i915_gem_objects.
+
 
 Detecting Unevictable Pages
 ---------------------------
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 347b3836c809..1c09d3e93c21 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2382,12 +2382,26 @@ void __i915_gem_object_invalidate(struct drm_i915_gem_object *obj)
 	invalidate_mapping_pages(mapping, 0, (loff_t)-1);
 }
 
+/**
+ * Move pages to appropriate lru and release the pagevec. Decrement the ref
+ * count of these pages.
+ */
+static inline void check_release_pagevec(struct pagevec *pvec)
+{
+	if (pagevec_count(pvec)) {
+		check_move_unevictable_pages(pvec);
+		__pagevec_release(pvec);
+		cond_resched();
+	}
+}
+
 static void
 i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj,
 			      struct sg_table *pages)
 {
 	struct sgt_iter sgt_iter;
 	struct page *page;
+	struct pagevec pvec;
 
 	__i915_gem_object_release_shmem(obj, pages, true);
 
@@ -2396,6 +2410,9 @@ i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj,
 	if (i915_gem_object_needs_bit17_swizzle(obj))
 		i915_gem_object_save_bit_17_swizzle(obj, pages);
 
+	mapping_clear_unevictable(file_inode(obj->base.filp)->i_mapping);
+
+	pagevec_init(&pvec);
 	for_each_sgt_page(page, sgt_iter, pages) {
 		if (obj->mm.dirty)
 			set_page_dirty(page);
@@ -2403,9 +2420,10 @@ i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj,
 		if (obj->mm.madv == I915_MADV_WILLNEED)
 			mark_page_accessed(page);
 
-		put_page(page);
-		cond_resched();
+		if (!pagevec_add(&pvec, page))
+			check_release_pagevec(&pvec);
 	}
+	check_release_pagevec(&pvec);
 	obj->mm.dirty = false;
 
 	sg_free_table(pages);
@@ -2528,6 +2546,7 @@ static int i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 	unsigned int sg_page_sizes;
 	gfp_t noreclaim;
 	int ret;
+	struct pagevec pvec;
 
 	/*
 	 * Assert that the object is not currently in any GPU domain. As it
@@ -2561,6 +2580,7 @@ static int i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 	 * Fail silently without starting the shrinker
 	 */
 	mapping = obj->base.filp->f_mapping;
+	mapping_set_unevictable(mapping);
 	noreclaim = mapping_gfp_constraint(mapping, ~__GFP_RECLAIM);
 	noreclaim |= __GFP_NORETRY | __GFP_NOWARN;
 
@@ -2675,8 +2695,12 @@ static int i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 err_sg:
 	sg_mark_end(sg);
 err_pages:
+	mapping_clear_unevictable(mapping);
+	pagevec_init(&pvec);
 	for_each_sgt_page(page, sgt_iter, st)
-		put_page(page);
+		if (!pagevec_add(&pvec, page))
+			check_release_pagevec(&pvec);
+	check_release_pagevec(&pvec);
 	sg_free_table(st);
 	kfree(st);
 
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 8e2c11e692ba..6c95df96c9aa 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -18,6 +18,8 @@ struct notifier_block;
 
 struct bio;
 
+struct pagevec;
+
 #define SWAP_FLAG_PREFER	0x8000	/* set if swap priority specified */
 #define SWAP_FLAG_PRIO_MASK	0x7fff
 #define SWAP_FLAG_PRIO_SHIFT	0
@@ -373,7 +375,7 @@ static inline int node_reclaim(struct pglist_data *pgdat, gfp_t mask,
 #endif
 
 extern int page_evictable(struct page *page);
-extern void check_move_unevictable_pages(struct page **, int nr_pages);
+extern void check_move_unevictable_pages(struct pagevec *pvec);
 
 extern int kswapd_run(int nid);
 extern void kswapd_stop(int nid);
diff --git a/mm/shmem.c b/mm/shmem.c
index 446942677cd4..0c3b005a59eb 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -781,7 +781,7 @@ void shmem_unlock_mapping(struct address_space *mapping)
 			break;
 		index = indices[pvec.nr - 1] + 1;
 		pagevec_remove_exceptionals(&pvec);
-		check_move_unevictable_pages(pvec.pages, pvec.nr);
+		check_move_unevictable_pages(&pvec);
 		pagevec_release(&pvec);
 		cond_resched();
 	}
diff --git a/mm/vmscan.c b/mm/vmscan.c
index c7ce2c161225..0dbc493026a2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -46,6 +46,7 @@
 #include <linux/delayacct.h>
 #include <linux/sysctl.h>
 #include <linux/oom.h>
+#include <linux/pagevec.h>
 #include <linux/prefetch.h>
 #include <linux/printk.h>
 #include <linux/dax.h>
@@ -4162,17 +4163,16 @@ int page_evictable(struct page *page)
 	return ret;
 }
 
-#ifdef CONFIG_SHMEM
 /**
- * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
- * @pages:	array of pages to check
- * @nr_pages:	number of pages to check
+ * check_move_unevictable_pages - check pages for evictability and move to
+ * appropriate zone lru list
+ * @pvec: pagevec with lru pages to check
  *
- * Checks pages for evictability and moves them to the appropriate lru list.
- *
- * This function is only used for SysV IPC SHM_UNLOCK.
+ * Checks pages for evictability, if an evictable page is in the unevictable
+ * lru list, moves it to the appropriate evictable lru list. This function
+ * should be only used for lru pages.
  */
-void check_move_unevictable_pages(struct page **pages, int nr_pages)
+void check_move_unevictable_pages(struct pagevec *pvec)
 {
 	struct lruvec *lruvec;
 	struct pglist_data *pgdat = NULL;
@@ -4180,8 +4180,8 @@ void check_move_unevictable_pages(struct page **pages, int nr_pages)
 	int pgrescued = 0;
 	int i;
 
-	for (i = 0; i < nr_pages; i++) {
-		struct page *page = pages[i];
+	for (i = 0; i < pvec->nr; i++) {
+		struct page *page = pvec->pages[i];
 		struct pglist_data *pagepgdat = page_pgdat(page);
 
 		pgscanned++;
@@ -4213,4 +4213,4 @@ void check_move_unevictable_pages(struct page **pages, int nr_pages)
 		spin_unlock_irq(&pgdat->lru_lock);
 	}
 }
-#endif /* CONFIG_SHMEM */
+EXPORT_SYMBOL_GPL(check_move_unevictable_pages);
-- 
2.19.1

Re: [PATCH v7] mm, drm/i915: mark pinned shmemfs pages as unevictable

[Kuo-Hsin Yang]

On Tue, Nov 6, 2018 at 9:23 PM Chris Wilson <chris@chris-wilson.co.uk> wrote:
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Signed-off-by: Kuo-Hsin Yang <vovoy@chromium.org>
> Acked-by: Michal Hocko <mhocko@suse.com> # mm part
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

Thanks for your fixes and review.

Re: [PATCH v6] mm, drm/i915: mark pinned shmemfs pages as unevictable

[Kuo-Hsin Yang]

On Tue, Nov 6, 2018 at 6:54 PM Daniel Vetter <daniel@ffwll.ch> wrote:
> There was ages ago some planes to have our own i915fs, so that we could
> overwrite the address_space hooks for page migration and eviction and that
> sort of thing, which would make all these pages evictable. Atm you have to
> ĥope our shrinker drops them on the floor, which I think is fairly
> confusing to core mm code (it's kinda like page eviction worked way back
> before rmaps).
>

Thanks for the explanation. Your blog posts helped a lot to get me
started on hacking drm/i915 driver.

> Just an side really.
> -Daniel
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

Re: [PATCH v7] mm, drm/i915: mark pinned shmemfs pages as unevictable

[Dave Hansen]

On 11/6/18 5:23 AM, Chris Wilson wrote:
> + (3) By the i915 driver to mark pinned address space until it's unpinned. The
> +     amount of unevictable memory marked by i915 driver is roughly the bounded
> +     object size in debugfs/dri/0/i915_gem_objects.

Thanks for adding this.  Feel free to add my:

Acked-by: Dave Hansen <dave.hansen@intel.com>

Re: [PATCH v7] mm, drm/i915: mark pinned shmemfs pages as unevictable

[Andrew Morton]

On Tue,  6 Nov 2018 13:23:24 +0000 Chris Wilson <chris@chris-wilson.co.uk> wrote:

> From: Kuo-Hsin Yang <vovoy@chromium.org>
> 
> The i915 driver uses shmemfs to allocate backing storage for gem
> objects. These shmemfs pages can be pinned (increased ref count) by
> shmem_read_mapping_page_gfp(). When a lot of pages are pinned, vmscan
> wastes a lot of time scanning these pinned pages. In some extreme case,
> all pages in the inactive anon lru are pinned, and only the inactive
> anon lru is scanned due to inactive_ratio, the system cannot swap and
> invokes the oom-killer. Mark these pinned pages as unevictable to speed
> up vmscan.
> 
> Export pagevec API check_move_unevictable_pages().
> 
> This patch was inspired by Chris Wilson's change [1].
> 
> [1]: https://patchwork.kernel.org/patch/9768741/
> 
> ...
>
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2382,12 +2382,26 @@ void __i915_gem_object_invalidate(struct drm_i915_gem_object *obj)
>  	invalidate_mapping_pages(mapping, 0, (loff_t)-1);
>  }
>  
> +/**

This token is used to introduce a kerneldoc comment.

> + * Move pages to appropriate lru and release the pagevec. Decrement the ref
> + * count of these pages.
> + */

But this isn't a kerneldoc comment.

At least, I don't think it is.  Maybe the parser got smarter when I
wasn't looking.

> +static inline void check_release_pagevec(struct pagevec *pvec)
> +{
> +	if (pagevec_count(pvec)) {
> +		check_move_unevictable_pages(pvec);
> +		__pagevec_release(pvec);
> +		cond_resched();
> +	}
> +}

This looks too large to be inlined and the compiler will ignore the
`inline' anyway.


Otherwise, Acked-by: Andrew Morton <akpm@linux-foundation.org>.  Please
go ahead and merge via the appropriate drm tree.

Re: [PATCH v7] mm, drm/i915: mark pinned shmemfs pages as unevictable

[Chris Wilson]

Quoting Andrew Morton (2018-11-06 18:12:11)
> On Tue,  6 Nov 2018 13:23:24 +0000 Chris Wilson <chris@chris-wilson.co.uk> wrote:
> 
> > From: Kuo-Hsin Yang <vovoy@chromium.org>
> > 
> > The i915 driver uses shmemfs to allocate backing storage for gem
> > objects. These shmemfs pages can be pinned (increased ref count) by
> > shmem_read_mapping_page_gfp(). When a lot of pages are pinned, vmscan
> > wastes a lot of time scanning these pinned pages. In some extreme case,
> > all pages in the inactive anon lru are pinned, and only the inactive
> > anon lru is scanned due to inactive_ratio, the system cannot swap and
> > invokes the oom-killer. Mark these pinned pages as unevictable to speed
> > up vmscan.
> > 
> > Export pagevec API check_move_unevictable_pages().
> > 
> > This patch was inspired by Chris Wilson's change [1].
> > 
> > [1]: https://patchwork.kernel.org/patch/9768741/
> > 
> > ...
> >
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -2382,12 +2382,26 @@ void __i915_gem_object_invalidate(struct drm_i915_gem_object *obj)
> >       invalidate_mapping_pages(mapping, 0, (loff_t)-1);
> >  }
> >  
> > +/**
> 
> This token is used to introduce a kerneldoc comment.
> 
> > + * Move pages to appropriate lru and release the pagevec. Decrement the ref
> > + * count of these pages.
> > + */
> 
> But this isn't a kerneldoc comment.
> 
> At least, I don't think it is.  Maybe the parser got smarter when I
> wasn't looking.
> 
> > +static inline void check_release_pagevec(struct pagevec *pvec)
> > +{
> > +     if (pagevec_count(pvec)) {
> > +             check_move_unevictable_pages(pvec);
> > +             __pagevec_release(pvec);
> > +             cond_resched();
> > +     }
> > +}
> 
> This looks too large to be inlined and the compiler will ignore the
> `inline' anyway.

Applied both corrections.

> Otherwise, Acked-by: Andrew Morton <akpm@linux-foundation.org>.  Please
> go ahead and merge via the appropriate drm tree.

Thank you, pushed to drm-intel, expected to arrive around 4.21.
-Chris