Re: [PATCH v3] drm: Optimise for continuous memory allocation
From: Arunpravin Paneer Selvam
Date: Mon Nov 28 2022 - 12:10:56 EST
Hi Xinhui,
On 11/28/2022 12:04 PM, xinhui pan wrote:
Currently drm-buddy does not have full knowledge of continuous memory.
Lets consider scenario below.
order 1: L R
order 0: LL LR RL RR
for order 1 allocation, it can offer L or R or LR+RL.
For now, we only implement L or R case for continuous memory allocation.
So this patch aims to implement the LR+RL case.
Signed-off-by: xinhui pan <xinhui.pan@xxxxxxx>
---
change from v2:
search continuous block in nearby root if needed
change from v1:
implement top-down continuous allocation
---
drivers/gpu/drm/drm_buddy.c | 78 +++++++++++++++++++++++++++++++++----
1 file changed, 71 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index 11bb59399471..ff58eb3136d2 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -386,6 +386,58 @@ alloc_range_bias(struct drm_buddy *mm,
return ERR_PTR(err);
}
+static struct drm_buddy_block *
+find_continuous_blocks(struct drm_buddy *mm,
+ int order,
+ unsigned long flags,
+ struct drm_buddy_block **rn)
+{
+ struct list_head *head = &mm->free_list[order];
+ struct drm_buddy_block *node, *parent, *free_node, *max_node = NULL;
NIT: We usually name the variable as *block or ***_block for drm buddy
and we have *node or ***_node for drm mm manager.
+ int i;
+
+ list_for_each_entry(free_node, head, link) {
+ if (max_node) {
+ if (!(flags & DRM_BUDDY_TOPDOWN_ALLOCATION))
+ break;
+
+ if (drm_buddy_block_offset(free_node) <
+ drm_buddy_block_offset(max_node))
+ continue;
+ }
+
+ parent = free_node;
+ do {
+ node = parent;
+ parent = parent->parent;
+ } while (parent && parent->right == node);
+
+ if (!parent) {
+ for (i = 0; i < mm->n_roots - 1; i++)
+ if (mm->roots[i] == node)
+ break;
+ if (i == mm->n_roots - 1)
+ continue;
+ node = mm->roots[i + 1];
+ } else {
+ node = parent->right;
+ }
+
+ while (drm_buddy_block_is_split(node))
+ node = node->left;
+
+ if (drm_buddy_block_is_free(node) &&
+ drm_buddy_block_order(node) == order) {
+ *rn = node;
+ max_node = free_node;
+ BUG_ON(drm_buddy_block_offset(node) !=
+ drm_buddy_block_offset(max_node) +
+ drm_buddy_block_size(mm, max_node));
+ }
+ }
+ return max_node;
+}
+
static struct drm_buddy_block *
get_maxblock(struct list_head *head)
{
@@ -637,7 +689,7 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
struct list_head *blocks,
unsigned long flags)
{
- struct drm_buddy_block *block = NULL;
+ struct drm_buddy_block *block = NULL, *rblock = NULL;
unsigned int min_order, order;
unsigned long pages;
LIST_HEAD(allocated);
@@ -689,17 +741,29 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
break;
if (order-- == min_order) {
+ if (!(flags & DRM_BUDDY_RANGE_ALLOCATION) &&
+ min_order != 0 && pages == BIT(order + 1)) {
+ block = find_continuous_blocks(mm,
+ order,
+ flags,
+ &rblock);
+ if (block)
+ break;
+ }
err = -ENOSPC;
goto err_free;
}
} while (1);
- mark_allocated(block);
- mm->avail -= drm_buddy_block_size(mm, block);
- kmemleak_update_trace(block);
- list_add_tail(&block->link, &allocated);
-
- pages -= BIT(order);
+ do {
+ mark_allocated(block);
+ mm->avail -= drm_buddy_block_size(mm, block);
+ kmemleak_update_trace(block);
+ list_add_tail(&block->link, &allocated);
+ pages -= BIT(order);
+ block = rblock;
+ rblock = NULL;
+ } while (block);
I think with this approach, if we are lucky enough we may get contiguous
blocks in one order level down in RL
combination from the freelist?
Regards,
Arun
if (!pages)
break;