[RFC PATCH v3 02/13] drm/ttm: Update the TTM swapout interface
Thomas Hellström
thomas.hellstrom at linux.intel.com
Fri Feb 10 09:49:12 UTC 2023
Update the TTM swapout interfaces for better compatibility with a shrinker.
- Replace number-of-pages int return with a long to better match the
kernel's shrinker interface.
- The gfp_flags parameter to ttm_xx_swapout() currently only takes the
GFP_KERNEL value and shouldn't really be needed since the shrinker we
hook up in upcoming patches sets a allocation context to match reclaim.
- Introduce a shrink reason enumeration and a driver callback to shrink
buffer objects.
The TTM_SHRINK_WATERMARK reason is going to still be handled using the
existing shmem copy, and will be used by pool types that don't lend
themselves well to shinking (dma_alloc pool) and when drivers explicitly
requests swapout.
The TTM_SHRINK_SWAP and TTM_SHRINK_PURGE reasons originate from a
shrinker and is to be handled by a new driver callback, bo_shrink().
Helpers for the new driver callback are provided in upcoming patches.
Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
---
drivers/gpu/drm/ttm/ttm_bo.c | 38 ++++++++++++++++++----
drivers/gpu/drm/ttm/ttm_device.c | 55 ++++++++++++++++++++++++--------
drivers/gpu/drm/ttm/ttm_tt.c | 23 ++++++-------
include/drm/ttm/ttm_bo.h | 4 +--
include/drm/ttm/ttm_device.h | 36 +++++++++++++++++++--
include/drm/ttm/ttm_tt.h | 17 ++++++++--
6 files changed, 134 insertions(+), 39 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 882c2fa346f3..e5c0970564c0 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -1114,13 +1114,29 @@ int ttm_bo_wait_ctx(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx)
}
EXPORT_SYMBOL(ttm_bo_wait_ctx);
-int ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
- gfp_t gfp_flags)
+/**
+ * ttm_bo_swapout() - Swap out or purge a buffer object
+ * @bo: The buffer object.
+ * @ctx: The ttm operation context.
+ * @reason: The swapout reason.
+ *
+ * Try to swap out or purge the contents of a system memory backed buffer
+ * object. The function needs to be called with the device's LRU lock held.
+ *
+ * Return: -EBUSY if the bo lock could not be grabbed or the object was
+ * otherwise busy. Otherwise the number of pages swapped out or negative
+ * error code on error. Iff the function didn't return -EBUSY, the
+ * LRU lock was dropped, and LRU traversal needs to restart.
+ */
+long ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
+ enum ttm_shrink_reason reason)
{
struct ttm_place place;
bool locked;
long ret;
+ lockdep_assert_held(&bo->bdev->lru_lock);
+
/*
* While the bo may already reside in SYSTEM placement, set
* SYSTEM as new placement to cover also the move further below.
@@ -1142,8 +1158,12 @@ int ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
}
if (bo->deleted) {
+ long num_pages = bo->ttm->num_pages;
+
ret = ttm_bo_cleanup_refs(bo, false, false, locked);
ttm_bo_put(bo);
+ if (!ret)
+ return num_pages;
return ret == -EBUSY ? -ENOSPC : ret;
}
@@ -1184,13 +1204,17 @@ int ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
* Swap out. Buffer will be swapped in again as soon as
* anyone tries to access a ttm page.
*/
- if (bo->bdev->funcs->swap_notify)
- bo->bdev->funcs->swap_notify(bo);
+ if (bo->bdev->funcs->bo_shrink && reason != TTM_SHRINK_WATERMARK) {
+ ret = bo->bdev->funcs->bo_shrink(bo, ctx);
+ } else {
+ if (bo->bdev->funcs->swap_notify)
+ bo->bdev->funcs->swap_notify(bo);
+ ret = ttm_tt_swapout(bo->bdev, bo->ttm);
+ if (!ret)
+ ret = bo->ttm->num_pages;
+ }
- if (ttm_tt_is_populated(bo->ttm))
- ret = ttm_tt_swapout(bo->bdev, bo->ttm, gfp_flags);
out:
-
/*
* Unreserve without putting on LRU to avoid swapping out an
* already swapped buffer.
diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index c7a1862f322a..49bb69c4e901 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -116,19 +116,28 @@ static int ttm_global_init(void)
return ret;
}
-/*
- * A buffer object shrink method that tries to swap out the first
- * buffer object on the global::swap_lru list.
+/**
+ * ttm_global_swapout() - Select and swap out a system-memory-backed bo.
+ * @ctx: The operation context.
+ * @reason: The reason for swapout.
+ *
+ * Select, based on round-robin a TTM device and traverse the LRUs of
+ * that specific device until a suitable bo backed by system memory is found
+ * and swapped-out or purged.
+ *
+ * Return: Positive value or zero indicating the size in pages of the
+ * bo swapped out. Negative error code on error.
*/
-int ttm_global_swapout(struct ttm_operation_ctx *ctx, gfp_t gfp_flags)
+long ttm_global_swapout(struct ttm_operation_ctx *ctx,
+ enum ttm_shrink_reason reason)
{
struct ttm_global *glob = &ttm_glob;
struct ttm_device *bdev;
- int ret = 0;
+ long ret = 0;
mutex_lock(&ttm_global_mutex);
list_for_each_entry(bdev, &glob->device_list, device_list) {
- ret = ttm_device_swapout(bdev, ctx, gfp_flags);
+ ret = ttm_device_swapout(bdev, ctx, reason);
if (ret > 0) {
list_move_tail(&bdev->device_list, &glob->device_list);
break;
@@ -139,14 +148,29 @@ int ttm_global_swapout(struct ttm_operation_ctx *ctx, gfp_t gfp_flags)
}
EXPORT_SYMBOL(ttm_global_swapout);
-int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
- gfp_t gfp_flags)
+/**
+ * ttm_device_swapout() - Select and swap out a system-memory-backed bo.
+ * @bdev: The device whos bos are considered for swapout.
+ * @ctx: The operation context.
+ * @reason: The reason for swapout.
+ *
+ * Traverse the LRUs of a specific device until a suitable bo backed by
+ * system memory is found and swapped-out or purged.
+ *
+ * Return: Positive value or zero indicating the size in pages of the
+ * bo swapped out. Negative error code on error.
+ */
+long ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
+ enum ttm_shrink_reason reason)
{
struct ttm_resource_cursor cursor;
struct ttm_resource_manager *man;
struct ttm_resource *res;
unsigned i;
- int ret;
+ long ret;
+
+ if (reason != TTM_SHRINK_WATERMARK && !bdev->funcs->bo_shrink)
+ return 0;
spin_lock(&bdev->lru_lock);
for (i = TTM_PL_SYSTEM; i < TTM_NUM_MEM_TYPES; ++i) {
@@ -156,16 +180,19 @@ int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
ttm_resource_manager_for_each_res(man, &cursor, res) {
struct ttm_buffer_object *bo = res->bo;
- uint32_t num_pages;
+ struct ttm_tt *tt;
if (!bo)
continue;
- num_pages = PFN_UP(bo->base.size);
- ret = ttm_bo_swapout(bo, ctx, gfp_flags);
+ tt = bo->ttm;
+ if (!tt || (reason == TTM_SHRINK_PURGE &&
+ !ttm_tt_purgeable(tt)))
+ continue;
+ ret = ttm_bo_swapout(bo, ctx, reason);
/* ttm_bo_swapout has dropped the lru_lock */
- if (!ret)
- return num_pages;
+ if (ret >= 0)
+ return ret;
if (ret != -EBUSY)
return ret;
}
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
index ab725d9d14a6..a68c14de0161 100644
--- a/drivers/gpu/drm/ttm/ttm_tt.c
+++ b/drivers/gpu/drm/ttm/ttm_tt.c
@@ -239,22 +239,21 @@ int ttm_tt_swapin(struct ttm_tt *ttm)
/**
* ttm_tt_swapout - swap out tt object
- *
* @bdev: TTM device structure.
* @ttm: The struct ttm_tt.
- * @gfp_flags: Flags to use for memory allocation.
*
- * Swapout a TT object to a shmem_file, return number of pages swapped out or
- * negative error code.
+ * Swapout a TT object to a shmem_file.
+ *
+ * Return: number of pages swapped out or negative error code on error.
*/
-int ttm_tt_swapout(struct ttm_device *bdev, struct ttm_tt *ttm,
- gfp_t gfp_flags)
+int ttm_tt_swapout(struct ttm_device *bdev, struct ttm_tt *ttm)
{
loff_t size = (loff_t)ttm->num_pages << PAGE_SHIFT;
struct address_space *swap_space;
struct file *swap_storage;
struct page *from_page;
struct page *to_page;
+ gfp_t gfp_flags;
int i, ret;
swap_storage = shmem_file_setup("ttm swap", size, 0);
@@ -264,7 +263,7 @@ int ttm_tt_swapout(struct ttm_device *bdev, struct ttm_tt *ttm,
}
swap_space = swap_storage->f_mapping;
- gfp_flags &= mapping_gfp_mask(swap_space);
+ gfp_flags = GFP_KERNEL & mapping_gfp_mask(swap_space);
for (i = 0; i < ttm->num_pages; ++i) {
from_page = ttm->pages[i];
@@ -315,12 +314,14 @@ int ttm_tt_populate(struct ttm_device *bdev,
while (atomic_long_read(&ttm_pages_allocated) > ttm_pages_limit ||
atomic_long_read(&ttm_dma32_pages_allocated) >
ttm_dma32_pages_limit) {
+ long r = ttm_global_swapout(ctx, TTM_SHRINK_WATERMARK);
- ret = ttm_global_swapout(ctx, GFP_KERNEL);
- if (ret == 0)
+ if (!r)
break;
- if (ret < 0)
+ if (r < 0) {
+ ret = r;
goto error;
+ }
}
if (bdev->funcs->ttm_tt_populate)
@@ -379,7 +380,7 @@ static int ttm_tt_debugfs_shrink_show(struct seq_file *m, void *data)
{
struct ttm_operation_ctx ctx = { false, false };
- seq_printf(m, "%d\n", ttm_global_swapout(&ctx, GFP_KERNEL));
+ seq_printf(m, "%ld\n", ttm_global_swapout(&ctx, TTM_SHRINK_SWAP));
return 0;
}
DEFINE_SHOW_ATTRIBUTE(ttm_tt_debugfs_shrink);
diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h
index 8b113c384236..6b45e0b639e0 100644
--- a/include/drm/ttm/ttm_bo.h
+++ b/include/drm/ttm/ttm_bo.h
@@ -375,8 +375,8 @@ void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map);
int ttm_bo_vmap(struct ttm_buffer_object *bo, struct iosys_map *map);
void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct iosys_map *map);
int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo);
-int ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
- gfp_t gfp_flags);
+long ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
+ enum ttm_shrink_reason reason);
void ttm_bo_pin(struct ttm_buffer_object *bo);
void ttm_bo_unpin(struct ttm_buffer_object *bo);
int ttm_mem_evict_first(struct ttm_device *bdev,
diff --git a/include/drm/ttm/ttm_device.h b/include/drm/ttm/ttm_device.h
index 4f3e81eac6f3..6bd2abf712ab 100644
--- a/include/drm/ttm/ttm_device.h
+++ b/include/drm/ttm/ttm_device.h
@@ -35,6 +35,21 @@ struct ttm_placement;
struct ttm_buffer_object;
struct ttm_operation_ctx;
+/**
+ * enum ttm_shrink_reason - Reason for shrinking system memory
+ * @TTM_SHRINK_WATERMARK - A watermark limit was reached. Not from reclaim.
+ * @TTM_SHRINK_PURGE - A request for shrinking only purged objects.
+ * @TTM_SHRINK_SWAP - A request for shrinking any object.
+ *
+ * This enum is intended for the buffer object- and shrink method selection
+ * algorithms. It's not intended to leak to or be used by TTM drivers.
+ */
+enum ttm_shrink_reason {
+ TTM_SHRINK_WATERMARK,
+ TTM_SHRINK_PURGE,
+ TTM_SHRINK_SWAP,
+};
+
/**
* struct ttm_global - Buffer object driver global data.
*/
@@ -207,6 +222,19 @@ struct ttm_device_funcs {
* adding fences that may force a delayed delete
*/
void (*release_notify)(struct ttm_buffer_object *bo);
+
+ /**
+ * Shrink the bo's system pages, Either by swapping or by purging.
+ * @bo: Bo the system pages of which are to be shrunken.
+ * @ctx: Operation ctx. In particular the driver callback should
+ * adhere to the no_wait_gpu and interruptible fields.
+ *
+ * This is also notifying the driver that the bo is about to be
+ * shrunken and the driver should take care to unbind any GPU bindings
+ * and to note that the content is purged if @bo->ttm is purgeable.
+ */
+ long (*bo_shrink)(struct ttm_buffer_object *bo,
+ struct ttm_operation_ctx *ctx);
};
/**
@@ -268,9 +296,11 @@ struct ttm_device {
struct workqueue_struct *wq;
};
-int ttm_global_swapout(struct ttm_operation_ctx *ctx, gfp_t gfp_flags);
-int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
- gfp_t gfp_flags);
+long ttm_global_swapout(struct ttm_operation_ctx *ctx,
+ enum ttm_shrink_reason reason);
+
+long ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
+ enum ttm_shrink_reason reason);
static inline struct ttm_resource_manager *
ttm_manager_type(struct ttm_device *bdev, int mem_type)
diff --git a/include/drm/ttm/ttm_tt.h b/include/drm/ttm/ttm_tt.h
index cc54be1912e1..627168eba8f6 100644
--- a/include/drm/ttm/ttm_tt.h
+++ b/include/drm/ttm/ttm_tt.h
@@ -87,6 +87,7 @@ struct ttm_tt {
#define TTM_TT_FLAG_ZERO_ALLOC BIT(1)
#define TTM_TT_FLAG_EXTERNAL BIT(2)
#define TTM_TT_FLAG_EXTERNAL_MAPPABLE BIT(3)
+#define TTM_TT_FLAG_DONTNEED BIT(4)
#define TTM_TT_FLAG_PRIV_POPULATED BIT(31)
uint32_t page_flags;
@@ -180,8 +181,8 @@ void ttm_tt_destroy(struct ttm_device *bdev, struct ttm_tt *ttm);
* Swap in a previously swap out ttm_tt.
*/
int ttm_tt_swapin(struct ttm_tt *ttm);
-int ttm_tt_swapout(struct ttm_device *bdev, struct ttm_tt *ttm,
- gfp_t gfp_flags);
+
+int ttm_tt_swapout(struct ttm_device *bdev, struct ttm_tt *ttm);
/**
* ttm_tt_populate - allocate pages for a ttm
@@ -223,6 +224,18 @@ void ttm_tt_mgr_init(unsigned long num_pages, unsigned long num_dma32_pages);
struct ttm_kmap_iter *ttm_kmap_iter_tt_init(struct ttm_kmap_iter_tt *iter_tt,
struct ttm_tt *tt);
+/**
+ * ttm_tt_purgeable() - Whether a struct ttm_tt's contents is purgeable
+ * @tt: The struct ttm_tt to consider.
+ *
+ * Return: Whether the contents is purgeable in the sence that the owner
+ * doesn't mind losing it as long as it gets notified.
+ */
+static inline bool ttm_tt_purgeable(struct ttm_tt *tt)
+{
+ return tt->page_flags & TTM_TT_FLAG_DONTNEED;
+}
+
#if IS_ENABLED(CONFIG_AGP)
#include <linux/agp_backend.h>
--
2.34.1
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