[PATCH 1/2] drm/ttm: rework ttm_tt page limit v2
Christian König
ckoenig.leichtzumerken at gmail.com
Wed Dec 16 14:04:26 UTC 2020
TTM implements a rather extensive accounting of allocated memory.
There are two reasons for this:
1. It tries to block userspace allocating a huge number of very small
BOs without accounting for the kmalloced memory.
2. Make sure we don't over allocate and run into an OOM situation
during swapout while trying to handle the memory shortage.
This is only partially a good idea. First of all it is perfectly
valid for an application to use all of system memory, limiting it to
50% is not really acceptable.
What we need to take care of is that the application is held
accountable for the memory it allocated. This is what control
mechanisms like memcg and the normal Linux page accounting already do.
Making sure that we don't run into an OOM situation while trying to
cope with a memory shortage is still a good idea, but this is also
not very well implemented since it means another opportunity of
recursion from the driver back into TTM.
So start to rework all of this by implementing a shrinker callback which
allows for TT object to be swapped out if necessary.
v2: Switch from limit to shrinker callback.
Signed-off-by: Christian König <christian.koenig at amd.com>
---
drivers/gpu/drm/ttm/ttm_bo.c | 4 +-
drivers/gpu/drm/ttm/ttm_memory.c | 7 ++-
drivers/gpu/drm/ttm/ttm_tt.c | 82 +++++++++++++++++++++++++++--
drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 2 +-
include/drm/ttm/ttm_bo_api.h | 2 +-
include/drm/ttm/ttm_tt.h | 6 ++-
6 files changed, 91 insertions(+), 12 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 31e8b3da5563..f1f3fd085465 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -1412,7 +1412,7 @@ EXPORT_SYMBOL(ttm_bo_wait);
* A buffer object shrink method that tries to swap out the first
* buffer object on the bo_global::swap_lru list.
*/
-int ttm_bo_swapout(struct ttm_operation_ctx *ctx)
+int ttm_bo_swapout(struct ttm_operation_ctx *ctx, gfp_t gfp_flags)
{
struct ttm_bo_global *glob = &ttm_bo_glob;
struct ttm_buffer_object *bo;
@@ -1495,7 +1495,7 @@ int ttm_bo_swapout(struct ttm_operation_ctx *ctx)
if (bo->bdev->driver->swap_notify)
bo->bdev->driver->swap_notify(bo);
- ret = ttm_tt_swapout(bo->bdev, bo->ttm);
+ ret = ttm_tt_swapout(bo->bdev, bo->ttm, gfp_flags);
out:
/**
diff --git a/drivers/gpu/drm/ttm/ttm_memory.c b/drivers/gpu/drm/ttm/ttm_memory.c
index a3bfbd9cea68..3d2479d0ce2c 100644
--- a/drivers/gpu/drm/ttm/ttm_memory.c
+++ b/drivers/gpu/drm/ttm/ttm_memory.c
@@ -37,6 +37,7 @@
#include <linux/slab.h>
#include <linux/swap.h>
#include <drm/ttm/ttm_pool.h>
+#include <drm/ttm/ttm_tt.h>
#include "ttm_module.h"
@@ -276,9 +277,9 @@ static void ttm_shrink(struct ttm_mem_global *glob, bool from_wq,
while (ttm_zones_above_swap_target(glob, from_wq, extra)) {
spin_unlock(&glob->lock);
- ret = ttm_bo_swapout(ctx);
+ ret = ttm_bo_swapout(ctx, 0);
spin_lock(&glob->lock);
- if (unlikely(ret != 0))
+ if (unlikely(ret < 0))
break;
}
@@ -453,6 +454,7 @@ int ttm_mem_global_init(struct ttm_mem_global *glob)
zone->name, (unsigned long long)zone->max_mem >> 10);
}
ttm_pool_mgr_init(glob->zone_kernel->max_mem/(2*PAGE_SIZE));
+ ttm_tt_mgr_init();
return 0;
out_no_zone:
ttm_mem_global_release(glob);
@@ -466,6 +468,7 @@ void ttm_mem_global_release(struct ttm_mem_global *glob)
/* let the page allocator first stop the shrink work. */
ttm_pool_mgr_fini();
+ ttm_tt_mgr_fini();
flush_workqueue(glob->swap_queue);
destroy_workqueue(glob->swap_queue);
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
index 7f75a13163f0..d454c428c56a 100644
--- a/drivers/gpu/drm/ttm/ttm_tt.c
+++ b/drivers/gpu/drm/ttm/ttm_tt.c
@@ -38,6 +38,8 @@
#include <drm/drm_cache.h>
#include <drm/ttm/ttm_bo_driver.h>
+static struct shrinker mm_shrinker;
+
/*
* Allocates a ttm structure for the given BO.
*/
@@ -223,13 +225,23 @@ int ttm_tt_swapin(struct ttm_tt *ttm)
return ret;
}
-int ttm_tt_swapout(struct ttm_bo_device *bdev, 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.
+ */
+int ttm_tt_swapout(struct ttm_bo_device *bdev, struct ttm_tt *ttm,
+ gfp_t gfp_flags)
{
struct address_space *swap_space;
struct file *swap_storage;
struct page *from_page;
struct page *to_page;
- gfp_t gfp_mask;
int i, ret;
swap_storage = shmem_file_setup("ttm swap",
@@ -241,14 +253,14 @@ int ttm_tt_swapout(struct ttm_bo_device *bdev, struct ttm_tt *ttm)
}
swap_space = swap_storage->f_mapping;
- gfp_mask = mapping_gfp_mask(swap_space);
+ gfp_flags |= mapping_gfp_mask(swap_space);
for (i = 0; i < ttm->num_pages; ++i) {
from_page = ttm->pages[i];
if (unlikely(from_page == NULL))
continue;
- to_page = shmem_read_mapping_page_gfp(swap_space, i, gfp_mask);
+ to_page = shmem_read_mapping_page_gfp(swap_space, i, gfp_flags);
if (IS_ERR(to_page)) {
ret = PTR_ERR(to_page);
goto out_err;
@@ -263,7 +275,7 @@ int ttm_tt_swapout(struct ttm_bo_device *bdev, struct ttm_tt *ttm)
ttm->swap_storage = swap_storage;
ttm->page_flags |= TTM_PAGE_FLAG_SWAPPED;
- return 0;
+ return ttm->num_pages;
out_err:
fput(swap_storage);
@@ -341,3 +353,63 @@ void ttm_tt_unpopulate(struct ttm_bo_device *bdev,
ttm_pool_free(&bdev->pool, ttm);
ttm->page_flags &= ~TTM_PAGE_FLAG_PRIV_POPULATED;
}
+
+/* As long as pages are available make sure to release at least one */
+static unsigned long ttm_tt_shrinker_scan(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ struct ttm_operation_ctx ctx = {
+ .no_wait_gpu = true
+ };
+ int ret;
+
+ if (sc->gfp_mask & GFP_NOFS)
+ return 0;
+
+ ret = ttm_bo_swapout(&ctx, GFP_NOFS);
+ return ret < 0 ? SHRINK_EMPTY : ret;
+}
+
+/* Return the number of pages available or SHRINK_EMPTY if we have none */
+static unsigned long ttm_tt_shrinker_count(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ struct ttm_buffer_object *bo;
+ unsigned long num_pages = 0;
+ unsigned int i;
+
+ if (sc->gfp_mask & GFP_NOFS)
+ return 0;
+
+ /* TODO: Is that to much overhead? */
+ spin_lock(&ttm_bo_glob.lru_lock);
+ for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i)
+ list_for_each_entry(bo, &ttm_bo_glob.swap_lru[i], swap)
+ num_pages += bo->ttm->num_pages;
+ spin_unlock(&ttm_bo_glob.lru_lock);
+
+ return num_pages ? num_pages : SHRINK_EMPTY;
+}
+
+/**
+ * ttm_tt_mgr_init - register with the MM shrinker
+ *
+ * Register with the MM shrinker for swapping out BOs.
+ */
+int ttm_tt_mgr_init(void)
+{
+ mm_shrinker.count_objects = ttm_tt_shrinker_count;
+ mm_shrinker.scan_objects = ttm_tt_shrinker_scan;
+ mm_shrinker.seeks = 1;
+ return register_shrinker(&mm_shrinker);
+}
+
+/**
+ * ttm_tt_mgr_fini - unregister our MM shrinker
+ *
+ * Unregisters the MM shrinker.
+ */
+void ttm_tt_mgr_fini(void)
+{
+ unregister_shrinker(&mm_shrinker);
+}
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
index 0008be02d31c..e141fa9f616d 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
@@ -1389,7 +1389,7 @@ static int vmw_pm_freeze(struct device *kdev)
vmw_execbuf_release_pinned_bo(dev_priv);
vmw_resource_evict_all(dev_priv);
vmw_release_device_early(dev_priv);
- while (ttm_bo_swapout(&ctx) == 0);
+ while (ttm_bo_swapout(&ctx, 0) > 0);
if (dev_priv->enable_fb)
vmw_fifo_resource_dec(dev_priv);
if (atomic_read(&dev_priv->num_fifo_resources) != 0) {
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index e17be324d95f..7c7539d76e1d 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -569,7 +569,7 @@ ssize_t ttm_bo_io(struct ttm_bo_device *bdev, struct file *filp,
const char __user *wbuf, char __user *rbuf,
size_t count, loff_t *f_pos, bool write);
-int ttm_bo_swapout(struct ttm_operation_ctx *ctx);
+int ttm_bo_swapout(struct ttm_operation_ctx *ctx, gfp_t gfp_flags);
/**
* ttm_bo_uses_embedded_gem_object - check if the given bo uses the
diff --git a/include/drm/ttm/ttm_tt.h b/include/drm/ttm/ttm_tt.h
index 6c8eb9a4de81..4bc3a08644fc 100644
--- a/include/drm/ttm/ttm_tt.h
+++ b/include/drm/ttm/ttm_tt.h
@@ -135,7 +135,8 @@ void ttm_tt_destroy_common(struct ttm_bo_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_bo_device *bdev, struct ttm_tt *ttm);
+int ttm_tt_swapout(struct ttm_bo_device *bdev, struct ttm_tt *ttm,
+ gfp_t gfp_flags);
/**
* ttm_tt_populate - allocate pages for a ttm
@@ -155,6 +156,9 @@ int ttm_tt_populate(struct ttm_bo_device *bdev, struct ttm_tt *ttm, struct ttm_o
*/
void ttm_tt_unpopulate(struct ttm_bo_device *bdev, struct ttm_tt *ttm);
+int ttm_tt_mgr_init(void);
+void ttm_tt_mgr_fini(void);
+
#if IS_ENABLED(CONFIG_AGP)
#include <linux/agp_backend.h>
--
2.25.1
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