drm/i915/i915_gem_evict.c

/*
 * Copyright © 2008-2010 Intel Corporation
 *
 * 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, sublicense,
 * 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 NONINFRINGEMENT.  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:
 *    Eric Anholt <eric@anholt.net>
 *    Chris Wilson <chris@chris-wilson.co.uuk>
 *
 */

#include "gem/i915_gem_context.h"
#include "gt/intel_gt.h"
#include "gt/intel_gt_requests.h"

#include "i915_drv.h"
#include "i915_gem_evict.h"
#include "i915_trace.h"

I915_SELFTEST_DECLARE(static struct igt_evict_ctl {
	bool fail_if_busy:1;
} igt_evict_ctl;)

static bool dying_vma(struct i915_vma *vma)
{
	return !kref_read(&vma->obj->base.refcount);
}

static int ggtt_flush(struct intel_gt *gt)
{
	/*
	 * Not everything in the GGTT is tracked via vma (otherwise we
	 * could evict as required with minimal stalling) so we are forced
	 * to idle the GPU and explicitly retire outstanding requests in
	 * the hopes that we can then remove contexts and the like only
	 * bound by their active reference.
	 */
	return intel_gt_wait_for_idle(gt, MAX_SCHEDULE_TIMEOUT);
}

static bool grab_vma(struct i915_vma *vma, struct i915_gem_ww_ctx *ww)
{
	/*
	 * We add the extra refcount so the object doesn't drop to zero until
	 * after ungrab_vma(), this way trylock is always paired with unlock.
	 */
	if (i915_gem_object_get_rcu(vma->obj)) {
		if (!i915_gem_object_trylock(vma->obj, ww)) {
			i915_gem_object_put(vma->obj);
			return false;
		}
	} else {
		/* Dead objects don't need pins */
		atomic_and(~I915_VMA_PIN_MASK, &vma->flags);
	}

	return true;
}

static void ungrab_vma(struct i915_vma *vma)
{
	if (dying_vma(vma))
		return;

	i915_gem_object_unlock(vma->obj);
	i915_gem_object_put(vma->obj);
}

static bool
mark_free(struct drm_mm_scan *scan,
	  struct i915_gem_ww_ctx *ww,
	  struct i915_vma *vma,
	  unsigned int flags,
	  struct list_head *unwind)
{
	if (i915_vma_is_pinned(vma))
		return false;

	if (!grab_vma(vma, ww))
		return false;

	list_add(&vma->evict_link, unwind);
	return drm_mm_scan_add_block(scan, &vma->node);
}

static bool defer_evict(struct i915_vma *vma)
{
	if (i915_vma_is_active(vma))
		return true;

	if (i915_vma_is_scanout(vma))
		return true;

	return false;
}

/**
 * i915_gem_evict_something - Evict vmas to make room for binding a new one
 * @vm: address space to evict from
 * @ww: An optional struct i915_gem_ww_ctx.
 * @min_size: size of the desired free space
 * @alignment: alignment constraint of the desired free space
 * @color: color for the desired space
 * @start: start (inclusive) of the range from which to evict objects
 * @end: end (exclusive) of the range from which to evict objects
 * @flags: additional flags to control the eviction algorithm
 *
 * This function will try to evict vmas until a free space satisfying the
 * requirements is found. Callers must check first whether any such hole exists
 * already before calling this function.
 *
 * This function is used by the object/vma binding code.
 *
 * Since this function is only used to free up virtual address space it only
 * ignores pinned vmas, and not object where the backing storage itself is
 * pinned. Hence obj->pages_pin_count does not protect against eviction.
 *
 * To clarify: This is for freeing up virtual address space, not for freeing
 * memory in e.g. the shrinker.
 */
int
i915_gem_evict_something(struct i915_address_space *vm,
			 struct i915_gem_ww_ctx *ww,
			 u64 min_size, u64 alignment,
			 unsigned long color,
			 u64 start, u64 end,
			 unsigned flags)
{
	struct drm_mm_scan scan;
	struct list_head eviction_list;
	struct i915_vma *vma, *next;
	struct drm_mm_node *node;
	enum drm_mm_insert_mode mode;
	struct i915_vma *active;
	int ret;

	lockdep_assert_held(&vm->mutex);
	trace_i915_gem_evict(vm, min_size, alignment, flags);

	/*
	 * The goal is to evict objects and amalgamate space in rough LRU order.
	 * Since both active and inactive objects reside on the same list,
	 * in a mix of creation and last scanned order, as we process the list
	 * we sort it into inactive/active, which keeps the active portion
	 * in a rough MRU order.
	 *
	 * The retirement sequence is thus:
	 *   1. Inactive objects (already retired, random order)
	 *   2. Active objects (will stall on unbinding, oldest scanned first)
	 */
	mode = DRM_MM_INSERT_BEST;
	if (flags & PIN_HIGH)
		mode = DRM_MM_INSERT_HIGH;
	if (flags & PIN_MAPPABLE)
		mode = DRM_MM_INSERT_LOW;
	drm_mm_scan_init_with_range(&scan, &vm->mm,
				    min_size, alignment, color,
				    start, end, mode);

	intel_gt_retire_requests(vm->gt);

search_again:
	active = NULL;
	INIT_LIST_HEAD(&eviction_list);
	list_for_each_entry_safe(vma, next, &vm->bound_list, vm_link) {
		if (vma == active) { /* now seen this vma twice */
			if (flags & PIN_NONBLOCK)
				break;

			active = ERR_PTR(-EAGAIN);
		}

		/*
		 * We keep this list in a rough least-recently scanned order
		 * of active elements (inactive elements are cheap to reap).
		 * New entries are added to the end, and we move anything we
		 * scan to the end. The assumption is that the working set
		 * of applications is either steady state (and thanks to the
		 * userspace bo cache it almost always is) or volatile and
		 * frequently replaced after a frame, which are self-evicting!
		 * Given that assumption, the MRU order of the scan list is
		 * fairly static, and keeping it in least-recently scan order
		 * is suitable.
		 *
		 * To notice when we complete one full cycle, we record the
		 * first active element seen, before moving it to the tail.
		 */
		if (active != ERR_PTR(-EAGAIN) && defer_evict(vma)) {
			if (!active)
				active = vma;

			list_move_tail(&vma->vm_link, &vm->bound_list);
			continue;
		}

		if (mark_free(&scan, ww, vma, flags, &eviction_list))
			goto found;
	}

	/* Nothing found, clean up and bail out! */
	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
		ret = drm_mm_scan_remove_block(&scan, &vma->node);
		BUG_ON(ret);
		ungrab_vma(vma);
	}

	/*
	 * Can we unpin some objects such as idle hw contents,
	 * or pending flips? But since only the GGTT has global entries
	 * such as scanouts, rinbuffers and contexts, we can skip the
	 * purge when inspecting per-process local address spaces.
	 */
	if (!i915_is_ggtt(vm) || flags & PIN_NONBLOCK)
		return -ENOSPC;

	/*
	 * Not everything in the GGTT is tracked via VMA using
	 * i915_vma_move_to_active(), otherwise we could evict as required
	 * with minimal stalling. Instead we are forced to idle the GPU and
	 * explicitly retire outstanding requests which will then remove
	 * the pinning for active objects such as contexts and ring,
	 * enabling us to evict them on the next iteration.
	 *
	 * To ensure that all user contexts are evictable, we perform
	 * a switch to the perma-pinned kernel context. This all also gives
	 * us a termination condition, when the last retired context is
	 * the kernel's there is no more we can evict.
	 */
	if (I915_SELFTEST_ONLY(igt_evict_ctl.fail_if_busy))
		return -EBUSY;

	ret = ggtt_flush(vm->gt);
	if (ret)
		return ret;

	cond_resched();

	flags |= PIN_NONBLOCK;
	goto search_again;

found:
	/* drm_mm doesn't allow any other other operations while
	 * scanning, therefore store to-be-evicted objects on a
	 * temporary list and take a reference for all before
	 * calling unbind (which may remove the active reference
	 * of any of our objects, thus corrupting the list).
	 */
	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
		if (drm_mm_scan_remove_block(&scan, &vma->node)) {
			__i915_vma_pin(vma);
		} else {
			list_del(&vma->evict_link);
			ungrab_vma(vma);
		}
	}

	/* Unbinding will emit any required flushes */
	ret = 0;
	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
		__i915_vma_unpin(vma);
		if (ret == 0)
			ret = __i915_vma_unbind(vma);
		ungrab_vma(vma);
	}

	while (ret == 0 && (node = drm_mm_scan_color_evict(&scan))) {
		vma = container_of(node, struct i915_vma, node);

		/* If we find any non-objects (!vma), we cannot evict them */
		if (vma->node.color != I915_COLOR_UNEVICTABLE &&
		    grab_vma(vma, ww)) {
			ret = __i915_vma_unbind(vma);
			ungrab_vma(vma);
		} else {
			ret = -ENOSPC;
		}
	}

	return ret;
}

/**
 * i915_gem_evict_for_node - Evict vmas to make room for binding a new one
 * @vm: address space to evict from
 * @ww: An optional struct i915_gem_ww_ctx.
 * @target: range (and color) to evict for
 * @flags: additional flags to control the eviction algorithm
 *
 * This function will try to evict vmas that overlap the target node.
 *
 * To clarify: This is for freeing up virtual address space, not for freeing
 * memory in e.g. the shrinker.
 */
int i915_gem_evict_for_node(struct i915_address_space *vm,
			    struct i915_gem_ww_ctx *ww,
			    struct drm_mm_node *target,
			    unsigned int flags)
{
	LIST_HEAD(eviction_list);
	struct drm_mm_node *node;
	u64 start = target->start;
	u64 end = start + target->size;
	struct i915_vma *vma, *next;
	int ret = 0;

	lockdep_assert_held(&vm->mutex);
	GEM_BUG_ON(!IS_ALIGNED(start, I915_GTT_PAGE_SIZE));
	GEM_BUG_ON(!IS_ALIGNED(end, I915_GTT_PAGE_SIZE));

	trace_i915_gem_evict_node(vm, target, flags);

	/*
	 * Retire before we search the active list. Although we have
	 * reasonable accuracy in our retirement lists, we may have
	 * a stray pin (preventing eviction) that can only be resolved by
	 * retiring.
	 */
	intel_gt_retire_requests(vm->gt);

	if (i915_vm_has_cache_coloring(vm)) {
		/* Expand search to cover neighbouring guard pages (or lack!) */
		if (start)
			start -= I915_GTT_PAGE_SIZE;

		/* Always look at the page afterwards to avoid the end-of-GTT */
		end += I915_GTT_PAGE_SIZE;
	}
	GEM_BUG_ON(start >= end);

	drm_mm_for_each_node_in_range(node, &vm->mm, start, end) {
		/* If we find any non-objects (!vma), we cannot evict them */
		if (node->color == I915_COLOR_UNEVICTABLE) {
			ret = -ENOSPC;
			break;
		}

		GEM_BUG_ON(!drm_mm_node_allocated(node));
		vma = container_of(node, typeof(*vma), node);

		/*
		 * If we are using coloring to insert guard pages between
		 * different cache domains within the address space, we have
		 * to check whether the objects on either side of our range
		 * abutt and conflict. If they are in conflict, then we evict
		 * those as well to make room for our guard pages.
		 */
		if (i915_vm_has_cache_coloring(vm)) {
			if (node->start + node->size == target->start) {
				if (node->color == target->color)
					continue;
			}
			if (node->start == target->start + target->size) {
				if (node->color == target->color)
					continue;
			}
		}

		if (i915_vma_is_pinned(vma)) {
			ret = -ENOSPC;
			break;
		}

		if (flags & PIN_NONBLOCK && i915_vma_is_active(vma)) {
			ret = -ENOSPC;
			break;
		}

		if (!grab_vma(vma, ww)) {
			ret = -ENOSPC;
			break;
		}

		/*
		 * Never show fear in the face of dragons!
		 *
		 * We cannot directly remove this node from within this
		 * iterator and as with i915_gem_evict_something() we employ
		 * the vma pin_count in order to prevent the action of
		 * unbinding one vma from freeing (by dropping its active
		 * reference) another in our eviction list.
		 */
		__i915_vma_pin(vma);
		list_add(&vma->evict_link, &eviction_list);
	}

	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
		__i915_vma_unpin(vma);
		if (ret == 0)
			ret = __i915_vma_unbind(vma);

		ungrab_vma(vma);
	}

	return ret;
}

/**
 * i915_gem_evict_vm - Evict all idle vmas from a vm
 * @vm: Address space to cleanse
 * @ww: An optional struct i915_gem_ww_ctx. If not NULL, i915_gem_evict_vm
 * will be able to evict vma's locked by the ww as well.
 * @busy_bo: Optional pointer to struct drm_i915_gem_object. If not NULL, then
 * in the event i915_gem_evict_vm() is unable to trylock an object for eviction,
 * then @busy_bo will point to it. -EBUSY is also returned. The caller must drop
 * the vm->mutex, before trying again to acquire the contended lock. The caller
 * also owns a reference to the object.
 *
 * This function evicts all vmas from a vm.
 *
 * This is used by the execbuf code as a last-ditch effort to defragment the
 * address space.
 *
 * To clarify: This is for freeing up virtual address space, not for freeing
 * memory in e.g. the shrinker.
 */
int i915_gem_evict_vm(struct i915_address_space *vm, struct i915_gem_ww_ctx *ww,
		      struct drm_i915_gem_object **busy_bo)
{
	int ret = 0;

	lockdep_assert_held(&vm->mutex);
	trace_i915_gem_evict_vm(vm);

	/* Switch back to the default context in order to unpin
	 * the existing context objects. However, such objects only
	 * pin themselves inside the global GTT and performing the
	 * switch otherwise is ineffective.
	 */
	if (i915_is_ggtt(vm)) {
		ret = ggtt_flush(vm->gt);
		if (ret)
			return ret;
	}

	do {
		struct i915_vma *vma, *vn;
		LIST_HEAD(eviction_list);
		LIST_HEAD(locked_eviction_list);

		list_for_each_entry(vma, &vm->bound_list, vm_link) {
			if (i915_vma_is_pinned(vma))
				continue;

			/*
			 * If we already own the lock, trylock fails. In case
			 * the resv is shared among multiple objects, we still
			 * need the object ref.
			 */
			if (!i915_gem_object_get_rcu(vma->obj) ||
			    (ww && (dma_resv_locking_ctx(vma->obj->base.resv) == &ww->ctx))) {
				__i915_vma_pin(vma);
				list_add(&vma->evict_link, &locked_eviction_list);
				continue;
			}

			if (!i915_gem_object_trylock(vma->obj, ww)) {
				if (busy_bo) {
					*busy_bo = vma->obj; /* holds ref */
					ret = -EBUSY;
					break;
				}
				i915_gem_object_put(vma->obj);
				continue;
			}

			__i915_vma_pin(vma);
			list_add(&vma->evict_link, &eviction_list);
		}
		if (list_empty(&eviction_list) && list_empty(&locked_eviction_list))
			break;

		/* Unbind locked objects first, before unlocking the eviction_list */
		list_for_each_entry_safe(vma, vn, &locked_eviction_list, evict_link) {
			__i915_vma_unpin(vma);

			if (ret == 0) {
				ret = __i915_vma_unbind(vma);
				if (ret != -EINTR) /* "Get me out of here!" */
					ret = 0;
			}
			if (!dying_vma(vma))
				i915_gem_object_put(vma->obj);
		}

		list_for_each_entry_safe(vma, vn, &eviction_list, evict_link) {
			__i915_vma_unpin(vma);
			if (ret == 0) {
				ret = __i915_vma_unbind(vma);
				if (ret != -EINTR) /* "Get me out of here!" */
					ret = 0;
			}

			i915_gem_object_unlock(vma->obj);
			i915_gem_object_put(vma->obj);
		}
	} while (ret == 0);

	return ret;
}

#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftests/i915_gem_evict.c"
#endif