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MEDIUM: shctx: Move list between hot and avail list in O(1)

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Instead of iterating over all the elements of a given row when moving it
between the hot and available lists, we can make use of the last_reserved
pointer that already points to the last block of the list to perform the
move in O(1).
This commit is contained in:
Remi Tricot-Le Breton 2023-11-16 17:38:12 +01:00 committed by William Lallemand
parent 55fbf82080
commit eccb97f60e
1 changed files with 20 additions and 21 deletions
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41
src/shctx.c
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@ -145,21 +145,21 @@ struct shared_block *shctx_row_reserve_hot(struct shared_context *shctx,
*/ */
void shctx_row_inc_hot(struct shared_context *shctx, struct shared_block *first) void shctx_row_inc_hot(struct shared_context *shctx, struct shared_block *first)
{ {
struct shared_block *block, *sblock;
int count = 0;
if (first->refcount <= 0) { if (first->refcount <= 0) {
block = first; BUG_ON(!first->last_reserved);
list_for_each_entry_safe_from(block, sblock, &shctx->avail, list) { /* Detach row from avail list, link first item's prev to last
* item's next. This allows to use the LIST_SPLICE_END_DETACHED
* macro. */
first->list.p->n = first->last_reserved->list.n;
first->last_reserved->list.n->p = first->list.p;
shctx_block_set_hot(shctx, block); /* Reattach to hot list */
first->list.p = &first->last_reserved->list;
LIST_SPLICE_END_DETACHED(&shctx->hot, &first->list);
count++; shctx->nbav -= first->block_count;
if (count >= first->block_count)
break;
}
} }
first->refcount++; first->refcount++;
@ -170,27 +170,26 @@ void shctx_row_inc_hot(struct shared_context *shctx, struct shared_block *first)
*/ */
void shctx_row_dec_hot(struct shared_context *shctx, struct shared_block *first) void shctx_row_dec_hot(struct shared_context *shctx, struct shared_block *first)
{ {
struct shared_block *block, *sblock;
int count = 0;
first->refcount--; first->refcount--;
if (first->refcount <= 0) { if (first->refcount <= 0) {
block = first; BUG_ON(!first->last_reserved);
list_for_each_entry_safe_from(block, sblock, &shctx->hot, list) { /* Detach row from hot list, link first item's prev to last
* item's next. This allows to use the LIST_SPLICE_END_DETACHED
* macro. */
first->list.p->n = first->last_reserved->list.n;
first->last_reserved->list.n->p = first->list.p;
shctx_block_set_avail(shctx, block); /* Reattach to avail list */
first->list.p = &first->last_reserved->list;
LIST_SPLICE_END_DETACHED(&shctx->avail, &first->list);
count++; shctx->nbav += first->block_count;
if (count >= first->block_count)
break;
} }
} }
}
/* /*
* Append data in the row if there is enough space. * Append data in the row if there is enough space.