drm/ttm: add pool wc/uc page allocator V3

On AGP system we might allocate/free routinely uncached or wc memory,
changing page from cached (wb) to uc or wc is very expensive and involves
a lot of flushing. To improve performance this allocator use a pool
of uc,wc pages.

Pools are protected with spinlocks to allow multiple threads to allocate pages
simultanously. Expensive operations are done outside of spinlock to maximize
concurrency.

Pools are linked lists of pages that were recently freed. mm shrink callback
allows kernel to claim back pages when they are required for something else.

Fixes:
* set_pages_array_wb handles highmem pages so we don't have to remove them
  from pool.
* Add count parameter to ttm_put_pages to avoid looping in free code.
* Change looping from _safe to normal in pool fill error path.
* Initialize sum variable and make the loop prettier in get_num_unused_pages.

* Moved pages_freed reseting inside the loop in ttm_page_pool_free.
* Add warning comment about spinlock context in ttm_page_pool_free.

Based on Jerome Glisse's and Dave Airlie's pool allocator.

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Pauli Nieminen <suokkos@gmail.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/ttm/Makefile

@@ -4,6 +4,6 @@
 ccflags-y := -Iinclude/drm
 ttm-y := ttm_agp_backend.o ttm_memory.o ttm_tt.o ttm_bo.o \
 	ttm_bo_util.o ttm_bo_vm.o ttm_module.o ttm_global.o \
-	ttm_object.o ttm_lock.o ttm_execbuf_util.o
+	ttm_object.o ttm_lock.o ttm_execbuf_util.o ttm_page_alloc.o
 
 obj-$(CONFIG_DRM_TTM) += ttm.o

drivers/gpu/drm/ttm/ttm_memory.c

@@ -27,6 +27,7 @@
 
 #include "ttm/ttm_memory.h"
 #include "ttm/ttm_module.h"
+#include "ttm/ttm_page_alloc.h"
 #include <linux/spinlock.h>
 #include <linux/sched.h>
 #include <linux/wait.h>
@@ -392,6 +393,7 @@ int ttm_mem_global_init(struct ttm_mem_global *glob)
 		       "Zone %7s: Available graphics memory: %llu kiB.\n",
 		       zone->name, (unsigned long long) zone->max_mem >> 10);
 	}
+	ttm_page_alloc_init(glob->zone_kernel->max_mem/(2*PAGE_SIZE));
 	return 0;
 out_no_zone:
 	ttm_mem_global_release(glob);
@@ -404,6 +406,9 @@ void ttm_mem_global_release(struct ttm_mem_global *glob)
 	unsigned int i;
 	struct ttm_mem_zone *zone;
 
+	/* let the page allocator first stop the shrink work. */
+	ttm_page_alloc_fini();
+
 	flush_workqueue(glob->swap_queue);
 	destroy_workqueue(glob->swap_queue);
 	glob->swap_queue = NULL;
@@ -411,7 +416,7 @@ void ttm_mem_global_release(struct ttm_mem_global *glob)
 		zone = glob->zones[i];
 		kobject_del(&zone->kobj);
 		kobject_put(&zone->kobj);
-	}
+			}
 	kobject_del(&glob->kobj);
 	kobject_put(&glob->kobj);
 }

drivers/gpu/drm/ttm/ttm_page_alloc.c

@@ -0,0 +1,711 @@
+/*
+ * Copyright (c) Red Hat Inc.
+
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sub license,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Authors: Dave Airlie <airlied@redhat.com>
+ *          Jerome Glisse <jglisse@redhat.com>
+ *          Pauli Nieminen <suokkos@gmail.com>
+ */
+
+/* simple list based uncached page pool
+ * - Pool collects resently freed pages for reuse
+ * - Use page->lru to keep a free list
+ * - doesn't track currently in use pages
+ */
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/highmem.h>
+#include <linux/mm_types.h>
+#include <linux/mm.h>
+
+#include <asm/atomic.h>
+#include <asm/agp.h>
+
+#include "ttm/ttm_bo_driver.h"
+#include "ttm/ttm_page_alloc.h"
+
+
+#define NUM_PAGES_TO_ALLOC		(PAGE_SIZE/sizeof(struct page *))
+#define SMALL_ALLOCATION		16
+#define FREE_ALL_PAGES			(~0U)
+/* times are in msecs */
+#define PAGE_FREE_INTERVAL		1000
+
+/**
+ * struct ttm_page_pool - Pool to reuse recently allocated uc/wc pages.
+ *
+ * @lock: Protects the shared pool from concurrnet access. Must be used with
+ * irqsave/irqrestore variants because pool allocator maybe called from
+ * delayed work.
+ * @fill_lock: Prevent concurrent calls to fill.
+ * @list: Pool of free uc/wc pages for fast reuse.
+ * @gfp_flags: Flags to pass for alloc_page.
+ * @npages: Number of pages in pool.
+ */
+struct ttm_page_pool {
+	spinlock_t		lock;
+	bool			fill_lock;
+	struct list_head	list;
+	int			gfp_flags;
+	unsigned		npages;
+};
+
+struct ttm_pool_opts {
+	unsigned	alloc_size;
+	unsigned	max_size;
+	unsigned	small;
+};
+
+#define NUM_POOLS 4
+
+/**
+ * struct ttm_pool_manager - Holds memory pools for fst allocation
+ *
+ * Manager is read only object for pool code so it doesn't need locking.
+ *
+ * @free_interval: minimum number of jiffies between freeing pages from pool.
+ * @page_alloc_inited: reference counting for pool allocation.
+ * @work: Work that is used to shrink the pool. Work is only run when there is
+ * some pages to free.
+ * @small_allocation: Limit in number of pages what is small allocation.
+ *
+ * @pools: All pool objects in use.
+ **/
+struct ttm_pool_manager {
+	struct shrinker		mm_shrink;
+	atomic_t		page_alloc_inited;
+	struct ttm_pool_opts	options;
+
+	union {
+		struct ttm_page_pool	pools[NUM_POOLS];
+		struct {
+			struct ttm_page_pool	wc_pool;
+			struct ttm_page_pool	uc_pool;
+			struct ttm_page_pool	wc_pool_dma32;
+			struct ttm_page_pool	uc_pool_dma32;
+		} ;
+	};
+};
+
+static struct ttm_pool_manager _manager = {
+	.page_alloc_inited	= ATOMIC_INIT(0)
+};
+
+#ifdef CONFIG_X86
+/* TODO: add this to x86 like _uc, this version here is inefficient */
+static int set_pages_array_wc(struct page **pages, int addrinarray)
+{
+	int i;
+
+	for (i = 0; i < addrinarray; i++)
+		set_memory_wc((unsigned long)page_address(pages[i]), 1);
+	return 0;
+}
+#else
+static int set_pages_array_wb(struct page **pages, int addrinarray)
+{
+#ifdef TTM_HAS_AGP
+	int i;
+
+	for (i = 0; i < addrinarray; i++)
+		unmap_page_from_agp(pages[i]);
+#endif
+	return 0;
+}
+
+static int set_pages_array_wc(struct page **pages, int addrinarray)
+{
+#ifdef TTM_HAS_AGP
+	int i;
+
+	for (i = 0; i < addrinarray; i++)
+		map_page_into_agp(pages[i]);
+#endif
+	return 0;
+}
+
+static int set_pages_array_uc(struct page **pages, int addrinarray)
+{
+#ifdef TTM_HAS_AGP
+	int i;
+
+	for (i = 0; i < addrinarray; i++)
+		map_page_into_agp(pages[i]);
+#endif
+	return 0;
+}
+#endif
+
+/**
+ * Select the right pool or requested caching state and ttm flags. */
+static struct ttm_page_pool *ttm_get_pool(int flags,
+		enum ttm_caching_state cstate)
+{
+	int pool_index;
+
+	if (cstate == tt_cached)
+		return NULL;
+
+	if (cstate == tt_wc)
+		pool_index = 0x0;
+	else
+		pool_index = 0x1;
+
+	if (flags & TTM_PAGE_FLAG_DMA32)
+		pool_index |= 0x2;
+
+	return &_manager.pools[pool_index];
+}
+
+/* set memory back to wb and free the pages. */
+static void ttm_pages_put(struct page *pages[], unsigned npages)
+{
+	unsigned i;
+	if (set_pages_array_wb(pages, npages))
+		printk(KERN_ERR "[ttm] Failed to set %d pages to wb!\n",
+				npages);
+	for (i = 0; i < npages; ++i)
+		__free_page(pages[i]);
+}
+
+static void ttm_pool_update_free_locked(struct ttm_page_pool *pool,
+		unsigned freed_pages)
+{
+	pool->npages -= freed_pages;
+}
+
+/**
+ * Free pages from pool.
+ *
+ * To prevent hogging the ttm_swap process we only free NUM_PAGES_TO_ALLOC
+ * number of pages in one go.
+ *
+ * @pool: to free the pages from
+ * @free_all: If set to true will free all pages in pool
+ **/
+static int ttm_page_pool_free(struct ttm_page_pool *pool, unsigned nr_free)
+{
+	unsigned long irq_flags;
+	struct page *p;
+	struct page **pages_to_free;
+	unsigned freed_pages = 0,
+		 npages_to_free = nr_free;
+
+	if (NUM_PAGES_TO_ALLOC < nr_free)
+		npages_to_free = NUM_PAGES_TO_ALLOC;
+
+	pages_to_free = kmalloc(npages_to_free * sizeof(struct page *),
+			GFP_KERNEL);
+	if (!pages_to_free) {
+		printk(KERN_ERR "Failed to allocate memory for pool free operation.\n");
+		return 0;
+	}
+
+restart:
+	spin_lock_irqsave(&pool->lock, irq_flags);
+
+	list_for_each_entry_reverse(p, &pool->list, lru) {
+		if (freed_pages >= npages_to_free)
+			break;
+
+		pages_to_free[freed_pages++] = p;
+		/* We can only remove NUM_PAGES_TO_ALLOC at a time. */
+		if (freed_pages >= NUM_PAGES_TO_ALLOC) {
+			/* remove range of pages from the pool */
+			__list_del(p->lru.prev, &pool->list);
+
+			ttm_pool_update_free_locked(pool, freed_pages);
+			/**
+			 * Because changing page caching is costly
+			 * we unlock the pool to prevent stalling.
+			 */
+			spin_unlock_irqrestore(&pool->lock, irq_flags);
+
+			ttm_pages_put(pages_to_free, freed_pages);
+			if (likely(nr_free != FREE_ALL_PAGES))
+				nr_free -= freed_pages;
+
+			if (NUM_PAGES_TO_ALLOC >= nr_free)
+				npages_to_free = nr_free;
+			else
+				npages_to_free = NUM_PAGES_TO_ALLOC;
+
+			freed_pages = 0;
+
+			/* free all so restart the processing */
+			if (nr_free)
+				goto restart;
+
+			/* Not allowed to fall tough or break because
+			 * following context is inside spinlock while we are
+			 * outside here.
+			 */
+			goto out;
+
+		}
+	}
+
+
+	/* remove range of pages from the pool */
+	if (freed_pages) {
+		__list_del(&p->lru, &pool->list);
+
+		ttm_pool_update_free_locked(pool, freed_pages);
+		nr_free -= freed_pages;
+	}
+
+	spin_unlock_irqrestore(&pool->lock, irq_flags);
+
+	if (freed_pages)
+		ttm_pages_put(pages_to_free, freed_pages);
+out:
+	kfree(pages_to_free);
+	return nr_free;
+}
+
+/* Get good estimation how many pages are free in pools */
+static int ttm_pool_get_num_unused_pages(void)
+{
+	unsigned i;
+	int total = 0;
+	for (i = 0; i < NUM_POOLS; ++i)
+		total += _manager.pools[i].npages;
+
+	return total;
+}
+
+/**
+ * Calback for mm to request pool to reduce number of page held.
+ */
+static int ttm_pool_mm_shrink(int shrink_pages, gfp_t gfp_mask)
+{
+	static atomic_t start_pool = ATOMIC_INIT(0);
+	unsigned i;
+	unsigned pool_offset = atomic_add_return(1, &start_pool);
+	struct ttm_page_pool *pool;
+
+	pool_offset = pool_offset % NUM_POOLS;
+	/* select start pool in round robin fashion */
+	for (i = 0; i < NUM_POOLS; ++i) {
+		unsigned nr_free = shrink_pages;
+		if (shrink_pages == 0)
+			break;
+		pool = &_manager.pools[(i + pool_offset)%NUM_POOLS];
+		shrink_pages = ttm_page_pool_free(pool, nr_free);
+	}
+	/* return estimated number of unused pages in pool */
+	return ttm_pool_get_num_unused_pages();
+}
+
+static void ttm_pool_mm_shrink_init(struct ttm_pool_manager *manager)
+{
+	manager->mm_shrink.shrink = &ttm_pool_mm_shrink;
+	manager->mm_shrink.seeks = 1;
+	register_shrinker(&manager->mm_shrink);
+}
+
+static void ttm_pool_mm_shrink_fini(struct ttm_pool_manager *manager)
+{
+	unregister_shrinker(&manager->mm_shrink);
+}
+
+static int ttm_set_pages_caching(struct page **pages,
+		enum ttm_caching_state cstate, unsigned cpages)
+{
+	int r = 0;
+	/* Set page caching */
+	switch (cstate) {
+	case tt_uncached:
+		r = set_pages_array_uc(pages, cpages);
+		if (r)
+			printk(KERN_ERR "[ttm] Failed to set %d pages to uc!\n",
+					cpages);
+		break;
+	case tt_wc:
+		r = set_pages_array_wc(pages, cpages);
+		if (r)
+			printk(KERN_ERR "[ttm] Failed to set %d pages to wc!\n",
+					cpages);
+		break;
+	default:
+		break;
+	}
+	return r;
+}
+
+/**
+ * Free pages the pages that failed to change the caching state. If there is
+ * any pages that have changed their caching state already put them to the
+ * pool.
+ */
+static void ttm_handle_caching_state_failure(struct list_head *pages,
+		int ttm_flags, enum ttm_caching_state cstate,
+		struct page **failed_pages, unsigned cpages)
+{
+	unsigned i;
+	/* Failed pages has to be reed */
+	for (i = 0; i < cpages; ++i) {
+		list_del(&failed_pages[i]->lru);
+		__free_page(failed_pages[i]);
+	}
+}
+
+/**
+ * Allocate new pages with correct caching.
+ *
+ * This function is reentrant if caller updates count depending on number of
+ * pages returned in pages array.
+ */
+static int ttm_alloc_new_pages(struct list_head *pages, int gfp_flags,
+		int ttm_flags, enum ttm_caching_state cstate, unsigned count)
+{
+	struct page **caching_array;
+	struct page *p;
+	int r = 0;
+	unsigned i, cpages;
+	unsigned max_cpages = min(count,
+			(unsigned)(PAGE_SIZE/sizeof(struct page *)));
+
+	/* allocate array for page caching change */
+	caching_array = kmalloc(max_cpages*sizeof(struct page *), GFP_KERNEL);
+
+	if (!caching_array) {
+		printk(KERN_ERR "[ttm] unable to allocate table for new pages.");
+		return -ENOMEM;
+	}
+
+	for (i = 0, cpages = 0; i < count; ++i) {
+		p = alloc_page(gfp_flags);
+
+		if (!p) {
+			printk(KERN_ERR "[ttm] unable to get page %u\n", i);
+
+			/* store already allocated pages in the pool after
+			 * setting the caching state */
+			if (cpages) {
+				r = ttm_set_pages_caching(caching_array, cstate, cpages);
+				if (r)
+					ttm_handle_caching_state_failure(pages,
+						ttm_flags, cstate,
+						caching_array, cpages);
+			}
+			r = -ENOMEM;
+			goto out;
+		}
+
+#ifdef CONFIG_HIGHMEM
+		/* gfp flags of highmem page should never be dma32 so we
+		 * we should be fine in such case
+		 */
+		if (!PageHighMem(p))
+#endif
+		{
+			caching_array[cpages++] = p;
+			if (cpages == max_cpages) {
+
+				r = ttm_set_pages_caching(caching_array,
+						cstate, cpages);
+				if (r) {
+					ttm_handle_caching_state_failure(pages,
+						ttm_flags, cstate,
+						caching_array, cpages);
+					goto out;
+				}
+				cpages = 0;
+			}
+		}
+
+		list_add(&p->lru, pages);
+	}
+
+	if (cpages) {
+		r = ttm_set_pages_caching(caching_array, cstate, cpages);
+		if (r)
+			ttm_handle_caching_state_failure(pages,
+					ttm_flags, cstate,
+					caching_array, cpages);
+	}
+out:
+	kfree(caching_array);
+
+	return r;
+}
+
+/**
+ * Fill the given pool if there isn't enough pages and requested number of
+ * pages is small.
+ */
+static void ttm_page_pool_fill_locked(struct ttm_page_pool *pool,
+		int ttm_flags, enum ttm_caching_state cstate, unsigned count,
+		unsigned long *irq_flags)
+{
+	struct page *p;
+	int r;
+	unsigned cpages = 0;
+	/**
+	 * Only allow one pool fill operation at a time.
+	 * If pool doesn't have enough pages for the allocation new pages are
+	 * allocated from outside of pool.
+	 */
+	if (pool->fill_lock)
+		return;
+
+	pool->fill_lock = true;
+
+	/* If allocation request is small and there is not enough
+	 * pages in pool we fill the pool first */
+	if (count < _manager.options.small
+		&& count > pool->npages) {
+		struct list_head new_pages;
+		unsigned alloc_size = _manager.options.alloc_size;
+
+		/**
+		 * Can't change page caching if in irqsave context. We have to
+		 * drop the pool->lock.
+		 */
+		spin_unlock_irqrestore(&pool->lock, *irq_flags);
+
+		INIT_LIST_HEAD(&new_pages);
+		r = ttm_alloc_new_pages(&new_pages, pool->gfp_flags, ttm_flags,
+				cstate,	alloc_size);
+		spin_lock_irqsave(&pool->lock, *irq_flags);
+
+		if (!r) {
+			list_splice(&new_pages, &pool->list);
+			pool->npages += alloc_size;
+		} else {
+			printk(KERN_ERR "[ttm] Failed to fill pool (%p).", pool);
+			/* If we have any pages left put them to the pool. */
+			list_for_each_entry(p, &pool->list, lru) {
+				++cpages;
+			}
+			list_splice(&new_pages, &pool->list);
+			pool->npages += cpages;
+		}
+
+	}
+	pool->fill_lock = false;
+}
+
+/**
+ * Cut count nubmer of pages from the pool and put them to return list
+ *
+ * @return count of pages still to allocate to fill the request.
+ */
+static unsigned ttm_page_pool_get_pages(struct ttm_page_pool *pool,
+		struct list_head *pages, int ttm_flags,
+		enum ttm_caching_state cstate, unsigned count)
+{
+	unsigned long irq_flags;
+	struct list_head *p;
+	unsigned i;
+
+	spin_lock_irqsave(&pool->lock, irq_flags);
+	ttm_page_pool_fill_locked(pool, ttm_flags, cstate, count, &irq_flags);
+
+	if (count >= pool->npages) {
+		/* take all pages from the pool */
+		list_splice_init(&pool->list, pages);
+		count -= pool->npages;
+		pool->npages = 0;
+		goto out;
+	}
+	/* find the last pages to include for requested number of pages. Split
+	 * pool to begin and halves to reduce search space. */
+	if (count <= pool->npages/2) {
+		i = 0;
+		list_for_each(p, &pool->list) {
+			if (++i == count)
+				break;
+		}
+	} else {
+		i = pool->npages + 1;
+		list_for_each_prev(p, &pool->list) {
+			if (--i == count)
+				break;
+		}
+	}
+	/* Cut count number of pages from pool */
+	list_cut_position(pages, &pool->list, p);
+	pool->npages -= count;
+	count = 0;
+out:
+	spin_unlock_irqrestore(&pool->lock, irq_flags);
+	return count;
+}
+
+/*
+ * On success pages list will hold count number of correctly
+ * cached pages.
+ */
+int ttm_get_pages(struct list_head *pages, int flags,
+		enum ttm_caching_state cstate, unsigned count)
+{
+	struct ttm_page_pool *pool = ttm_get_pool(flags, cstate);
+	struct page *p = NULL;
+	int gfp_flags = 0;
+	int r;
+
+	/* set zero flag for page allocation if required */
+	if (flags & TTM_PAGE_FLAG_ZERO_ALLOC)
+		gfp_flags |= __GFP_ZERO;
+
+	/* No pool for cached pages */
+	if (pool == NULL) {
+		if (flags & TTM_PAGE_FLAG_DMA32)
+			gfp_flags |= GFP_DMA32;
+		else
+			gfp_flags |= __GFP_HIGHMEM;
+
+		for (r = 0; r < count; ++r) {
+			p = alloc_page(gfp_flags);
+			if (!p) {
+
+				printk(KERN_ERR "[ttm] unable to allocate page.");
+				return -ENOMEM;
+			}
+
+			list_add(&p->lru, pages);
+		}
+		return 0;
+	}
+
+
+	/* combine zero flag to pool flags */
+	gfp_flags |= pool->gfp_flags;
+
+	/* First we take pages from the pool */
+	count = ttm_page_pool_get_pages(pool, pages, flags, cstate, count);
+
+	/* clear the pages coming from the pool if requested */
+	if (flags & TTM_PAGE_FLAG_ZERO_ALLOC) {
+		list_for_each_entry(p, pages, lru) {
+			clear_page(page_address(p));
+		}
+	}
+
+	/* If pool didn't have enough pages allocate new one. */
+	if (count > 0) {
+		/* ttm_alloc_new_pages doesn't reference pool so we can run
+		 * multiple requests in parallel.
+		 **/
+		r = ttm_alloc_new_pages(pages, gfp_flags, flags, cstate, count);
+		if (r) {
+			/* If there is any pages in the list put them back to
+			 * the pool. */
+			printk(KERN_ERR "[ttm] Failed to allocate extra pages "
+					"for large request.");
+			ttm_put_pages(pages, 0, flags, cstate);
+			return r;
+		}
+	}
+
+
+	return 0;
+}
+
+/* Put all pages in pages list to correct pool to wait for reuse */
+void ttm_put_pages(struct list_head *pages, unsigned page_count, int flags,
+		enum ttm_caching_state cstate)
+{
+	unsigned long irq_flags;
+	struct ttm_page_pool *pool = ttm_get_pool(flags, cstate);
+	struct page *p, *tmp;
+
+	if (pool == NULL) {
+		/* No pool for this memory type so free the pages */
+
+		list_for_each_entry_safe(p, tmp, pages, lru) {
+			__free_page(p);
+		}
+		/* Make the pages list empty */
+		INIT_LIST_HEAD(pages);
+		return;
+	}
+	if (page_count == 0) {
+		list_for_each_entry_safe(p, tmp, pages, lru) {
+			++page_count;
+		}
+	}
+
+	spin_lock_irqsave(&pool->lock, irq_flags);
+	list_splice_init(pages, &pool->list);
+	pool->npages += page_count;
+	/* Check that we don't go over the pool limit */
+	page_count = 0;
+	if (pool->npages > _manager.options.max_size) {
+		page_count = pool->npages - _manager.options.max_size;
+		/* free at least NUM_PAGES_TO_ALLOC number of pages
+		 * to reduce calls to set_memory_wb */
+		if (page_count < NUM_PAGES_TO_ALLOC)
+			page_count = NUM_PAGES_TO_ALLOC;
+	}
+	spin_unlock_irqrestore(&pool->lock, irq_flags);
+	if (page_count)
+		ttm_page_pool_free(pool, page_count);
+}
+
+static void ttm_page_pool_init_locked(struct ttm_page_pool *pool, int flags)
+{
+	spin_lock_init(&pool->lock);
+	pool->fill_lock = false;
+	INIT_LIST_HEAD(&pool->list);
+	pool->npages = 0;
+	pool->gfp_flags = flags;
+}
+
+int ttm_page_alloc_init(unsigned max_pages)
+{
+	if (atomic_add_return(1, &_manager.page_alloc_inited) > 1)
+		return 0;
+
+	printk(KERN_INFO "[ttm] Initializing pool allocator.\n");
+
+	ttm_page_pool_init_locked(&_manager.wc_pool, GFP_HIGHUSER);
+
+	ttm_page_pool_init_locked(&_manager.uc_pool, GFP_HIGHUSER);
+
+	ttm_page_pool_init_locked(&_manager.wc_pool_dma32, GFP_USER | GFP_DMA32);
+
+	ttm_page_pool_init_locked(&_manager.uc_pool_dma32, GFP_USER | GFP_DMA32);
+
+	_manager.options.max_size = max_pages;
+	_manager.options.small = SMALL_ALLOCATION;
+	_manager.options.alloc_size = NUM_PAGES_TO_ALLOC;
+
+	ttm_pool_mm_shrink_init(&_manager);
+
+	return 0;
+}
+
+void ttm_page_alloc_fini()
+{
+	int i;
+
+	if (atomic_sub_return(1, &_manager.page_alloc_inited) > 0)
+		return;
+
+	printk(KERN_INFO "[ttm] Finilizing pool allocator.\n");
+	ttm_pool_mm_shrink_fini(&_manager);
+
+	for (i = 0; i < NUM_POOLS; ++i)
+		ttm_page_pool_free(&_manager.pools[i], FREE_ALL_PAGES);
+}

drivers/gpu/drm/ttm/ttm_tt.c

@@ -38,6 +38,7 @@
 #include "ttm/ttm_module.h"
 #include "ttm/ttm_bo_driver.h"
 #include "ttm/ttm_placement.h"
+#include "ttm/ttm_page_alloc.h"
 
 static int ttm_tt_swapin(struct ttm_tt *ttm);
 
@@ -55,21 +56,6 @@ static void ttm_tt_free_page_directory(struct ttm_tt *ttm)
 	ttm->pages = NULL;
 }
 
-static struct page *ttm_tt_alloc_page(unsigned page_flags)
-{
-	gfp_t gfp_flags = GFP_USER;
-
-	if (page_flags & TTM_PAGE_FLAG_ZERO_ALLOC)
-		gfp_flags |= __GFP_ZERO;
-
-	if (page_flags & TTM_PAGE_FLAG_DMA32)
-		gfp_flags |= __GFP_DMA32;
-	else
-		gfp_flags |= __GFP_HIGHMEM;
-
-	return alloc_page(gfp_flags);
-}
-
 static void ttm_tt_free_user_pages(struct ttm_tt *ttm)
 {
 	int write;
@@ -110,15 +96,21 @@ static void ttm_tt_free_user_pages(struct ttm_tt *ttm)
 static struct page *__ttm_tt_get_page(struct ttm_tt *ttm, int index)
 {
 	struct page *p;
+	struct list_head h;
 	struct ttm_mem_global *mem_glob = ttm->glob->mem_glob;
 	int ret;
 
 	while (NULL == (p = ttm->pages[index])) {
-		p = ttm_tt_alloc_page(ttm->page_flags);
 
-		if (!p)
+		INIT_LIST_HEAD(&h);
+
+		ret = ttm_get_pages(&h, ttm->page_flags, ttm->caching_state, 1);
+
+		if (ret != 0)
 			return NULL;
 
+		p = list_first_entry(&h, struct page, lru);
+
 		ret = ttm_mem_global_alloc_page(mem_glob, p, false, false);
 		if (unlikely(ret != 0))
 			goto out_err;
@@ -227,10 +219,10 @@ static int ttm_tt_set_caching(struct ttm_tt *ttm,
 	if (ttm->caching_state == c_state)
 		return 0;
 
-	if (c_state != tt_cached) {
-		ret = ttm_tt_populate(ttm);
-		if (unlikely(ret != 0))
-			return ret;
+	if (ttm->state == tt_unpopulated) {
+		/* Change caching but don't populate */
+		ttm->caching_state = c_state;
+		return 0;
 	}
 
 	if (ttm->caching_state == tt_cached)
@@ -281,13 +273,17 @@ EXPORT_SYMBOL(ttm_tt_set_placement_caching);
 static void ttm_tt_free_alloced_pages(struct ttm_tt *ttm)
 {
 	int i;
+	unsigned count = 0;
+	struct list_head h;
 	struct page *cur_page;
 	struct ttm_backend *be = ttm->be;
 
+	INIT_LIST_HEAD(&h);
+
 	if (be)
 		be->func->clear(be);
-	(void)ttm_tt_set_caching(ttm, tt_cached);
 	for (i = 0; i < ttm->num_pages; ++i) {
+
 		cur_page = ttm->pages[i];
 		ttm->pages[i] = NULL;
 		if (cur_page) {
@@ -297,9 +293,11 @@ static void ttm_tt_free_alloced_pages(struct ttm_tt *ttm)
 				       "Leaking pages.\n");
 			ttm_mem_global_free_page(ttm->glob->mem_glob,
 						 cur_page);
-			__free_page(cur_page);
+			list_add(&cur_page->lru, &h);
+			count++;
 		}
 	}
+	ttm_put_pages(&h, count, ttm->page_flags, ttm->caching_state);
 	ttm->state = tt_unpopulated;
 	ttm->first_himem_page = ttm->num_pages;
 	ttm->last_lomem_page = -1;

include/drm/ttm/ttm_page_alloc.h

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) Red Hat Inc.
+
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sub license,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Authors: Dave Airlie <airlied@redhat.com>
+ *          Jerome Glisse <jglisse@redhat.com>
+ */
+#ifndef TTM_PAGE_ALLOC
+#define TTM_PAGE_ALLOC
+
+#include "ttm_bo_driver.h"
+#include "ttm_memory.h"
+
+/**
+ * Get count number of pages from pool to pages list.
+ *
+ * @pages: heado of empty linked list where pages are filled.
+ * @flags: ttm flags for page allocation.
+ * @cstate: ttm caching state for the page.
+ * @count: number of pages to allocate.
+ */
+int ttm_get_pages(struct list_head *pages,
+		  int flags,
+		  enum ttm_caching_state cstate,
+		  unsigned count);
+/**
+ * Put linked list of pages to pool.
+ *
+ * @pages: list of pages to free.
+ * @page_count: number of pages in the list. Zero can be passed for unknown
+ * count.
+ * @flags: ttm flags for page allocation.
+ * @cstate: ttm caching state.
+ */
+void ttm_put_pages(struct list_head *pages,
+		   unsigned page_count,
+		   int flags,
+		   enum ttm_caching_state cstate);
+/**
+ * Initialize pool allocator.
+ *
+ * Pool allocator is internaly reference counted so it can be initialized
+ * multiple times but ttm_page_alloc_fini has to be called same number of
+ * times.
+ */
+int ttm_page_alloc_init(unsigned max_pages);
+/**
+ * Free pool allocator.
+ */
+void ttm_page_alloc_fini(void);
+
+#endif