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Message-Id: <20220818121114.20862-1-zhangpeng.00@bytedance.com>
Date: Thu, 18 Aug 2022 20:11:14 +0800
From: Peng Zhang <zhangpeng.00@...edance.com>
To: joro@...tes.org, will@...nel.org
Cc: iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
"zhangpeng.00" <zhangpeng.00@...edance.com>
Subject: [PATCH] optimize iommu allocate iova
From: "zhangpeng.00" <zhangpeng.00@...edance.com>
Signed-off-by: zhangpeng.00 <zhangpeng.00@...edance.com>
---
drivers/iommu/iova.c | 411 ++++++++++++++++++++++++++++++-------------
include/linux/iova.h | 8 +-
2 files changed, 297 insertions(+), 122 deletions(-)
diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index db77aa675145..58e500e316d6 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -43,6 +43,166 @@ static struct iova *to_iova(struct rb_node *node)
return rb_entry(node, struct iova, node);
}
+/*
+* gap_flag is a bits map.
+* We can allocate 2^order size area without any fragmentation
+* in range [low, high) if the corresponding bit was set.
+*
+* This function computes gap_flag for a given range [low, high)
+* in time complexity log(n).
+*/
+static unsigned long __compute_gap_flag(unsigned long low, unsigned long high)
+{
+ unsigned long gap_flag = 0;
+
+ while (low < high) {
+ int order = __ffs64(high);
+ unsigned long delta;
+
+ if (low > high - (1UL << order))
+ order = fls_long(high -low) -1;
+ delta = 1UL << order;
+ gap_flag |= delta;
+ high -= delta;
+ }
+ return gap_flag;
+}
+
+/*
+* This function return a start adress within [low, high) which is
+* 2^split_order aligned and can be used to allocate the maximum
+* 2^split_order size area.
+*
+* The time complexity of this function is log(n).
+*/
+static
+unsigned long split(unsigned long low, unsigned long high, int split_order)
+{
+ unsigned long best_low = ~0UL;
+ int best_order = 128;
+
+ while (low < high) {
+ int order = __ffs64(high);
+ unsigned long delta;
+
+ if (low > high - (1UL << order))
+ order = fls_long(high -low) - 1;
+ delta = 1UL << order;
+ if (order < best_order && order >= split_order) {
+ best_low = high - (1UL << split_order);
+ if(order == split_order)
+ break;
+ best_order = order;
+ }
+ high -= delta;
+ }
+ return best_low;
+}
+
+static inline unsigned long prev_iova_high(struct iova *iova)
+{
+ return iova->prev_iova ? iova->prev_iova->pfn_hi + 1 : 0;
+}
+
+static inline unsigned long iova_compute_gap_flag(struct iova *iova)
+{
+ return __compute_gap_flag(prev_iova_high(iova), iova->pfn_lo);
+}
+
+/*
+* Called by rbtree_augmented to maintain subtree_gap_flag.
+*
+* iova->subtree_gap_flag =
+* rb_entry(iova->node.rb_left) ->subtree_gap_flag |
+* rb_entry(iova->node.rb_right)->subtree_gap_flag |
+* ioa->gap_flag
+*/
+static inline bool iova_gap_callbacks_compute_or(struct iova *iova, bool exit)
+{
+ struct iova *child;
+ unsigned long subtree_gap_flag = iova->gap_flag;
+
+ if (iova->node.rb_left) {
+ child = rb_entry(iova->node.rb_left, struct iova, node);
+ subtree_gap_flag |= child->subtree_gap_flag;
+ }
+ if (iova->node.rb_right) {
+ child = rb_entry(iova->node.rb_right, struct iova, node);
+ subtree_gap_flag |= child->subtree_gap_flag;
+ }
+ if (exit && iova->subtree_gap_flag == subtree_gap_flag)
+ return true;
+ iova->subtree_gap_flag = subtree_gap_flag;
+ return false;
+}
+
+RB_DECLARE_CALLBACKS(static, iova_gap_callbacks, struct iova, node,
+ subtree_gap_flag,
+ iova_gap_callbacks_compute_or)
+
+/*
+* If a iova's gap_flag has been chanegd, we shoud call this function to maintain
+* the subtree_gap_flag in rbtree.
+*
+* The time complexity of this function is log(n).
+*/
+static inline void iova_subtree_gap_flag_update(struct iova *iova)
+{
+ iova_gap_callbacks_propagate(&iova->node, NULL);
+}
+
+static inline int __better_gap_flag(unsigned long first_flag,
+ unsigned long second_flag)
+{
+ return __ffs64(second_flag) < __ffs64(first_flag) ? 2 : 1;
+}
+
+/*
+* Compare two gap_flag to choose the more appropriate gap_flag to allocate.
+* return 1: first_flag
+* return 2: second_second
+* return 0: they are all not satisfied
+*/
+static int better_gap_flag(unsigned long first_flag,
+ unsigned long second_flag, int order)
+{
+ first_flag >>= order;
+ second_flag >>= order;
+
+ if (first_flag) {
+ if(second_flag)
+ return __better_gap_flag(first_flag, second_flag);
+ return 1;
+ }
+ return second_flag ? 2 : 0;
+}
+
+static inline void choose_better_gap(struct iova *iova,
+ struct iova **best_iova,
+ unsigned long *best_gap_flag,
+ bool *check_subtree,
+ unsigned long order)
+{
+ if (better_gap_flag(*best_gap_flag, iova->gap_flag, order) == 2) {
+ *best_iova = iova;
+ *best_gap_flag = iova->gap_flag;
+ *check_subtree = false;
+ }
+}
+
+static inline void choose_better_gap_subtree(struct iova *iova,
+ struct iova **best_iova,
+ unsigned long *best_gap_flag,
+ bool *check_subtree,
+ unsigned long order)
+{
+ if (better_gap_flag(*best_gap_flag, iova->subtree_gap_flag, order) == 2) {
+ *best_iova = iova;
+ *best_gap_flag = iova->subtree_gap_flag;
+ *check_subtree = true;
+ }
+}
+
void
init_iova_domain(struct iova_domain *iovad, unsigned long granule,
unsigned long start_pfn)
@@ -56,90 +216,37 @@ init_iova_domain(struct iova_domain *iovad, unsigned long granule,
spin_lock_init(&iovad->iova_rbtree_lock);
iovad->rbroot = RB_ROOT;
- iovad->cached_node = &iovad->anchor.node;
- iovad->cached32_node = &iovad->anchor.node;
iovad->granule = granule;
iovad->start_pfn = start_pfn;
iovad->dma_32bit_pfn = 1UL << (32 - iova_shift(iovad));
- iovad->max32_alloc_size = iovad->dma_32bit_pfn;
+
iovad->anchor.pfn_lo = iovad->anchor.pfn_hi = IOVA_ANCHOR;
+ iovad->anchor.prev_iova = NULL;
+ iovad->anchor.gap_flag = __compute_gap_flag(0, IOVA_ANCHOR);
+ iovad->anchor.subtree_gap_flag = iovad->anchor.gap_flag;
+
rb_link_node(&iovad->anchor.node, NULL, &iovad->rbroot.rb_node);
rb_insert_color(&iovad->anchor.node, &iovad->rbroot);
-}
-EXPORT_SYMBOL_GPL(init_iova_domain);
-
-static struct rb_node *
-__get_cached_rbnode(struct iova_domain *iovad, unsigned long limit_pfn)
-{
- if (limit_pfn <= iovad->dma_32bit_pfn)
- return iovad->cached32_node;
- return iovad->cached_node;
-}
-
-static void
-__cached_rbnode_insert_update(struct iova_domain *iovad, struct iova *new)
-{
- if (new->pfn_hi < iovad->dma_32bit_pfn)
- iovad->cached32_node = &new->node;
- else
- iovad->cached_node = &new->node;
-}
-
-static void
-__cached_rbnode_delete_update(struct iova_domain *iovad, struct iova *free)
-{
- struct iova *cached_iova;
-
- cached_iova = to_iova(iovad->cached32_node);
- if (free == cached_iova ||
- (free->pfn_hi < iovad->dma_32bit_pfn &&
- free->pfn_lo >= cached_iova->pfn_lo))
- iovad->cached32_node = rb_next(&free->node);
-
- if (free->pfn_lo < iovad->dma_32bit_pfn)
- iovad->max32_alloc_size = iovad->dma_32bit_pfn;
-
- cached_iova = to_iova(iovad->cached_node);
- if (free->pfn_lo >= cached_iova->pfn_lo)
- iovad->cached_node = rb_next(&free->node);
+ if(start_pfn)
+ reserve_iova(iovad, 0, start_pfn - 1);
}
+EXPORT_SYMBOL_GPL(init_iova_domain);
-static struct rb_node *iova_find_limit(struct iova_domain *iovad, unsigned long limit_pfn)
+static struct rb_node *iova_find_limit(struct iova_domain *iovad,
+ unsigned long limit_pfn)
{
- struct rb_node *node, *next;
- /*
- * Ideally what we'd like to judge here is whether limit_pfn is close
- * enough to the highest-allocated IOVA that starting the allocation
- * walk from the anchor node will be quicker than this initial work to
- * find an exact starting point (especially if that ends up being the
- * anchor node anyway). This is an incredibly crude approximation which
- * only really helps the most likely case, but is at least trivially easy.
- */
- if (limit_pfn > iovad->dma_32bit_pfn)
- return &iovad->anchor.node;
-
- node = iovad->rbroot.rb_node;
- while (to_iova(node)->pfn_hi < limit_pfn)
- node = node->rb_right;
-
-search_left:
- while (node->rb_left && to_iova(node->rb_left)->pfn_lo >= limit_pfn)
- node = node->rb_left;
-
- if (!node->rb_left)
- return node;
-
- next = node->rb_left;
- while (next->rb_right) {
- next = next->rb_right;
- if (to_iova(next)->pfn_lo >= limit_pfn) {
- node = next;
- goto search_left;
- }
+ struct rb_node *curr = iovad->rbroot.rb_node;
+ while (curr) {
+ struct iova *iova = to_iova(curr);
+ if (limit_pfn - 1 > iova->pfn_hi)
+ curr = curr->rb_right;
+ else if (limit_pfn > prev_iova_high(iova))
+ break;
+ else
+ curr = curr->rb_left;
}
-
- return node;
+ return curr;
}
/* Insert the iova into domain rbtree by holding writer lock */
@@ -148,6 +255,7 @@ iova_insert_rbtree(struct rb_root *root, struct iova *iova,
struct rb_node *start)
{
struct rb_node **new, *parent = NULL;
+ struct iova *next_iova;
new = (start) ? &start : &(root->rb_node);
/* Figure out where to put new node */
@@ -166,69 +274,129 @@ iova_insert_rbtree(struct rb_root *root, struct iova *iova,
}
}
/* Add new node and rebalance tree. */
+
rb_link_node(&iova->node, parent, new);
- rb_insert_color(&iova->node, root);
+
+ next_iova = to_iova(rb_next(&iova->node));
+ iova->prev_iova = next_iova->prev_iova;
+ next_iova->prev_iova = iova;
+
+ iova->gap_flag = iova_compute_gap_flag(iova);
+ next_iova->gap_flag = iova_compute_gap_flag(next_iova);
+
+ iova_subtree_gap_flag_update(iova);
+ iova_subtree_gap_flag_update(next_iova);
+
+ rb_insert_augmented(&iova->node, root, &iova_gap_callbacks);
}
+
static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
unsigned long size, unsigned long limit_pfn,
struct iova *new, bool size_aligned)
{
- struct rb_node *curr, *prev;
- struct iova *curr_iova;
+ int order = fls_long(size - 1);
unsigned long flags;
- unsigned long new_pfn, retry_pfn;
- unsigned long align_mask = ~0UL;
- unsigned long high_pfn = limit_pfn, low_pfn = iovad->start_pfn;
+ struct rb_node *curr;
+ struct rb_node *parent;
+ struct iova *curr_iova;
+ unsigned long start_pfn;
+ bool ignore = false;
+ struct iova *best_iova = NULL;
+ unsigned long best_gap_flag;
+ bool check_subtree;
- if (size_aligned)
- align_mask <<= fls_long(size - 1);
+ BUG_ON(limit_pfn == 0);
- /* Walk the tree backwards */
spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
- if (limit_pfn <= iovad->dma_32bit_pfn &&
- size >= iovad->max32_alloc_size)
- goto iova32_full;
+ curr = iova_find_limit(iovad, limit_pfn);
- curr = __get_cached_rbnode(iovad, limit_pfn);
curr_iova = to_iova(curr);
- retry_pfn = curr_iova->pfn_hi + 1;
+ best_gap_flag = __compute_gap_flag(prev_iova_high(curr_iova),
+ min(limit_pfn , curr_iova->pfn_lo));
-retry:
- do {
- high_pfn = min(high_pfn, curr_iova->pfn_lo);
- new_pfn = (high_pfn - size) & align_mask;
- prev = curr;
- curr = rb_prev(curr);
- curr_iova = to_iova(curr);
- } while (curr && new_pfn <= curr_iova->pfn_hi && new_pfn >= low_pfn);
-
- if (high_pfn < size || new_pfn < low_pfn) {
- if (low_pfn == iovad->start_pfn && retry_pfn < limit_pfn) {
- high_pfn = limit_pfn;
- low_pfn = retry_pfn;
- curr = iova_find_limit(iovad, limit_pfn);
+ /*
+ * Check limit_iova whether it can allocate from
+ * the gap between it and it's previous iova.
+ */
+ if (better_gap_flag(0, best_gap_flag, order) == 2) {
+ best_iova = curr_iova;
+ check_subtree = false;
+ }
+
+ while (true) {
+ /*
+ * Check the left sub_tree whether it has a better gap.
+ */
+ if (!ignore && curr->rb_left) {
+ curr_iova = to_iova(curr->rb_left);
+ choose_better_gap_subtree(curr_iova, &best_iova,
+ &best_gap_flag, &check_subtree, order);
+ }
+
+ parent = rb_parent(curr);
+ if (parent == NULL)
+ break;
+ /*
+ * If current node is the left child of it parent,
+ * the parent node and the parent's right sub_tree should not
+ * to be checked because they exceed the limit_pfn.
+ */
+ ignore = parent->rb_left == curr;
+ curr = parent;
+
+ /*
+ * Check the current rbtree_node whether it is better.
+ */
+ if (!ignore) {
curr_iova = to_iova(curr);
- goto retry;
+ choose_better_gap(curr_iova, &best_iova,
+ &best_gap_flag, &check_subtree, order);
}
- iovad->max32_alloc_size = size;
- goto iova32_full;
}
- /* pfn_lo will point to size aligned address if size_aligned is set */
- new->pfn_lo = new_pfn;
- new->pfn_hi = new->pfn_lo + size - 1;
+ if (!best_iova) {
+ spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
+ return -ENOMEM;
+ }
- /* If we have 'prev', it's a valid place to start the insertion. */
- iova_insert_rbtree(&iovad->rbroot, new, prev);
- __cached_rbnode_insert_update(iovad, new);
+ /*
+ * If best_gap is in a sub_tree, we should find where it is.
+ */
+ if (check_subtree) {
+ int best_order = __ffs(best_gap_flag & (~0UL << order));
+
+ curr = &best_iova->node;
+ while (true) {
+ if(curr->rb_right &&
+ to_iova(curr->rb_right)->subtree_gap_flag &
+ (1UL << best_order)) {
+ curr = curr->rb_right;
+ continue;
+ }
- spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
- return 0;
+ if (to_iova(curr)->gap_flag & (1UL << best_order))
+ break;
-iova32_full:
+ curr = curr->rb_left;
+ /*
+ * Due to the subtree_gap_flag, curr is NULL should be
+ * impossible. We must find the best appropriate gap
+ * to allocate.
+ */
+ BUG_ON(!curr);
+ }
+ best_iova = to_iova(curr);
+ }
+
+ start_pfn = split(prev_iova_high(best_iova),
+ min(best_iova->pfn_lo, limit_pfn), order);
+
+ new->pfn_lo = start_pfn;
+ new->pfn_hi = start_pfn + size - 1;
+ iova_insert_rbtree(&iovad->rbroot, new, &best_iova->node);
spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
- return -ENOMEM;
+ return 0;
}
static struct kmem_cache *iova_cache;
@@ -324,7 +492,6 @@ alloc_iova(struct iova_domain *iovad, unsigned long size,
free_iova_mem(new_iova);
return NULL;
}
-
return new_iova;
}
EXPORT_SYMBOL_GPL(alloc_iova);
@@ -352,9 +519,14 @@ private_find_iova(struct iova_domain *iovad, unsigned long pfn)
static void remove_iova(struct iova_domain *iovad, struct iova *iova)
{
+ struct iova *next_iova;
assert_spin_locked(&iovad->iova_rbtree_lock);
- __cached_rbnode_delete_update(iovad, iova);
- rb_erase(&iova->node, &iovad->rbroot);
+
+ next_iova = to_iova(rb_next(&iova->node));
+ next_iova->prev_iova = iova->prev_iova;
+ next_iova->gap_flag = iova_compute_gap_flag(next_iova);
+ iova_subtree_gap_flag_update(next_iova);
+ rb_erase_augmented(&iova->node, &iovad->rbroot, &iova_gap_callbacks);
}
/**
@@ -554,8 +726,11 @@ static void
__adjust_overlap_range(struct iova *iova,
unsigned long *pfn_lo, unsigned long *pfn_hi)
{
- if (*pfn_lo < iova->pfn_lo)
+ if (*pfn_lo < iova->pfn_lo) {
iova->pfn_lo = *pfn_lo;
+ iova->gap_flag = iova_compute_gap_flag(iova);
+ iova_subtree_gap_flag_update(iova);
+ }
if (*pfn_hi > iova->pfn_hi)
*pfn_lo = iova->pfn_hi + 1;
}
diff --git a/include/linux/iova.h b/include/linux/iova.h
index 320a70e40233..95cf1793cd0b 100644
--- a/include/linux/iova.h
+++ b/include/linux/iova.h
@@ -11,7 +11,7 @@
#include <linux/types.h>
#include <linux/kernel.h>
-#include <linux/rbtree.h>
+#include <linux/rbtree_augmented.h>
#include <linux/dma-mapping.h>
/* iova structure */
@@ -19,6 +19,9 @@ struct iova {
struct rb_node node;
unsigned long pfn_hi; /* Highest allocated pfn */
unsigned long pfn_lo; /* Lowest allocated pfn */
+ struct iova *prev_iova;
+ unsigned long gap_flag;
+ unsigned long subtree_gap_flag;
};
@@ -28,12 +31,9 @@ struct iova_rcache;
struct iova_domain {
spinlock_t iova_rbtree_lock; /* Lock to protect update of rbtree */
struct rb_root rbroot; /* iova domain rbtree root */
- struct rb_node *cached_node; /* Save last alloced node */
- struct rb_node *cached32_node; /* Save last 32-bit alloced node */
unsigned long granule; /* pfn granularity for this domain */
unsigned long start_pfn; /* Lower limit for this domain */
unsigned long dma_32bit_pfn;
- unsigned long max32_alloc_size; /* Size of last failed allocation */
struct iova anchor; /* rbtree lookup anchor */
struct iova_rcache *rcaches;
--
2.20.1
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