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iommu/iova: Extend rbtree node caching 

The cached node mechanism provides a significant performance benefit for
allocations using a 32-bit DMA mask, but in the case of non-PCI devices
or where the 32-bit space is full, the loss of this benefit can be
significant - on large systems there can be many thousands of entries in
the tree, such that walking all the way down to find free space every
time becomes increasingly awful.

Maintain a similar cached node for the whole IOVA space as a superset of
the 32-bit space so that performance can remain much more consistent.

Inspired by work by Zhen Lei <thunder.leizhen@huawei.com>.

Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Zhen Lei <thunder.leizhen@huawei.com>
Tested-by: Nate Watterson <nwatters@codeaurora.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Robin Murphy 2017-09-21 16:52:44 +01:00 committed by Joerg Roedel
parent 086c83acb7
commit e60aa7b538
2 changed files with 30 additions and 33 deletions
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60
drivers/iommu/iova.c
View File

@ -48,6 +48,7 @@ init_iova_domain(struct iova_domain *iovad, unsigned long granule,
spin_lock_init(&iovad->iova_rbtree_lock);
iovad->rbroot = RB_ROOT;
iovad->cached_node = NULL;
iovad->cached32_node = NULL;
iovad->granule = granule;
iovad->start_pfn = start_pfn;
@ -110,48 +111,44 @@ EXPORT_SYMBOL_GPL(init_iova_flush_queue);
static struct rb_node *
__get_cached_rbnode(struct iova_domain *iovad, unsigned long *limit_pfn)
{
if ((*limit_pfn > iovad->dma_32bit_pfn) ||
(iovad->cached32_node == NULL))
struct rb_node *cached_node = NULL;
struct iova *curr_iova;
if (*limit_pfn <= iovad->dma_32bit_pfn)
cached_node = iovad->cached32_node;
if (!cached_node)
cached_node = iovad->cached_node;
if (!cached_node)
return rb_last(&iovad->rbroot);
else {
struct rb_node *prev_node = rb_prev(iovad->cached32_node);
struct iova *curr_iova =
rb_entry(iovad->cached32_node, struct iova, node);
*limit_pfn = curr_iova->pfn_lo;
return prev_node;
}
curr_iova = rb_entry(cached_node, struct iova, node);
*limit_pfn = min(*limit_pfn, curr_iova->pfn_lo);
return rb_prev(cached_node);
}
static void
__cached_rbnode_insert_update(struct iova_domain *iovad,
unsigned long limit_pfn, struct iova *new)
__cached_rbnode_insert_update(struct iova_domain *iovad, struct iova *new)
{
if (limit_pfn != iovad->dma_32bit_pfn)
return;
iovad->cached32_node = &new->node;
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;
struct rb_node *curr;
if (!iovad->cached32_node)
return;
curr = iovad->cached32_node;
cached_iova = rb_entry(curr, struct iova, node);
cached_iova = rb_entry(iovad->cached32_node, struct iova, node);
if (free->pfn_hi < iovad->dma_32bit_pfn &&
iovad->cached32_node && free->pfn_lo >= cached_iova->pfn_lo)
iovad->cached32_node = rb_next(&free->node);
if (free->pfn_lo >= cached_iova->pfn_lo) {
struct rb_node *node = rb_next(&free->node);
struct iova *iova = rb_entry(node, struct iova, node);
/* only cache if it's below 32bit pfn */
if (node && iova->pfn_lo < iovad->dma_32bit_pfn)
iovad->cached32_node = node;
else
iovad->cached32_node = NULL;
}
cached_iova = rb_entry(iovad->cached_node, struct iova, node);
if (iovad->cached_node && free->pfn_lo >= cached_iova->pfn_lo)
iovad->cached_node = rb_next(&free->node);
}
/* Insert the iova into domain rbtree by holding writer lock */
@ -188,7 +185,7 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
{
struct rb_node *prev, *curr = NULL;
unsigned long flags;
unsigned long saved_pfn, new_pfn;
unsigned long new_pfn;
unsigned long align_mask = ~0UL;
if (size_aligned)
@ -196,7 +193,6 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
/* Walk the tree backwards */
spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
saved_pfn = limit_pfn;
curr = __get_cached_rbnode(iovad, &limit_pfn);
prev = curr;
while (curr) {
@ -226,7 +222,7 @@ move_left:
/* 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, saved_pfn, new);
__cached_rbnode_insert_update(iovad, new);
spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);

3
include/linux/iova.h
View File

@ -70,7 +70,8 @@ struct iova_fq {
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 *cached32_node; /* Save last alloced node */
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;