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authorJoe Thornber <ejt@redhat.com>2014-10-10 16:42:10 +0100
committerMike Snitzer <snitzer@redhat.com>2014-11-10 15:25:28 -0500
commitac4c3f34a9af63092b3fbfafe34c3e966fbd96c5 (patch)
tree2ec28fb1bb3888f092acdc4957e7b06f3751dc82
parent23ca2bb6c6104db9d4cff4e33cbabee303c49d4d (diff)
downloadlinux-ac4c3f34a9af63092b3fbfafe34c3e966fbd96c5.tar.gz
dm thin: sort the deferred cells
Sort the cells in logical block order before processing each cell in process_thin_deferred_cells(). This significantly improves the ondisk layout on rotational storage, whereby improving read performance. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
-rw-r--r--drivers/md/dm-thin.c88
1 files changed, 68 insertions, 20 deletions
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 3f3a66124d46..b9d25026ab84 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -17,6 +17,7 @@
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
+#include <linux/sort.h>
#include <linux/rbtree.h>
#define DM_MSG_PREFIX "thin"
@@ -205,6 +206,8 @@ typedef void (*process_bio_fn)(struct thin_c *tc, struct bio *bio);
typedef void (*process_cell_fn)(struct thin_c *tc, struct dm_bio_prison_cell *cell);
typedef void (*process_mapping_fn)(struct dm_thin_new_mapping *m);
+#define CELL_SORT_ARRAY_SIZE 8192
+
struct pool {
struct list_head list;
struct dm_target *ti; /* Only set if a pool target is bound */
@@ -252,6 +255,8 @@ struct pool {
process_mapping_fn process_prepared_mapping;
process_mapping_fn process_prepared_discard;
+
+ struct dm_bio_prison_cell *cell_sort_array[CELL_SORT_ARRAY_SIZE];
};
static enum pool_mode get_pool_mode(struct pool *pool);
@@ -1800,12 +1805,48 @@ static void process_thin_deferred_bios(struct thin_c *tc)
blk_finish_plug(&plug);
}
+static int cmp_cells(const void *lhs, const void *rhs)
+{
+ struct dm_bio_prison_cell *lhs_cell = *((struct dm_bio_prison_cell **) lhs);
+ struct dm_bio_prison_cell *rhs_cell = *((struct dm_bio_prison_cell **) rhs);
+
+ BUG_ON(!lhs_cell->holder);
+ BUG_ON(!rhs_cell->holder);
+
+ if (lhs_cell->holder->bi_iter.bi_sector < rhs_cell->holder->bi_iter.bi_sector)
+ return -1;
+
+ if (lhs_cell->holder->bi_iter.bi_sector > rhs_cell->holder->bi_iter.bi_sector)
+ return 1;
+
+ return 0;
+}
+
+static unsigned sort_cells(struct pool *pool, struct list_head *cells)
+{
+ unsigned count = 0;
+ struct dm_bio_prison_cell *cell, *tmp;
+
+ list_for_each_entry_safe(cell, tmp, cells, user_list) {
+ if (count >= CELL_SORT_ARRAY_SIZE)
+ break;
+
+ pool->cell_sort_array[count++] = cell;
+ list_del(&cell->user_list);
+ }
+
+ sort(pool->cell_sort_array, count, sizeof(cell), cmp_cells, NULL);
+
+ return count;
+}
+
static void process_thin_deferred_cells(struct thin_c *tc)
{
struct pool *pool = tc->pool;
unsigned long flags;
struct list_head cells;
- struct dm_bio_prison_cell *cell, *tmp;
+ struct dm_bio_prison_cell *cell;
+ unsigned i, j, count;
INIT_LIST_HEAD(&cells);
@@ -1816,27 +1857,34 @@ static void process_thin_deferred_cells(struct thin_c *tc)
if (list_empty(&cells))
return;
- list_for_each_entry_safe(cell, tmp, &cells, user_list) {
- BUG_ON(!cell->holder);
+ do {
+ count = sort_cells(tc->pool, &cells);
- /*
- * If we've got no free new_mapping structs, and processing
- * this bio might require one, we pause until there are some
- * prepared mappings to process.
- */
- if (ensure_next_mapping(pool)) {
- spin_lock_irqsave(&tc->lock, flags);
- list_add(&cell->user_list, &tc->deferred_cells);
- list_splice(&cells, &tc->deferred_cells);
- spin_unlock_irqrestore(&tc->lock, flags);
- break;
- }
+ for (i = 0; i < count; i++) {
+ cell = pool->cell_sort_array[i];
+ BUG_ON(!cell->holder);
- if (cell->holder->bi_rw & REQ_DISCARD)
- pool->process_discard_cell(tc, cell);
- else
- pool->process_cell(tc, cell);
- }
+ /*
+ * If we've got no free new_mapping structs, and processing
+ * this bio might require one, we pause until there are some
+ * prepared mappings to process.
+ */
+ if (ensure_next_mapping(pool)) {
+ for (j = i; j < count; j++)
+ list_add(&pool->cell_sort_array[j]->user_list, &cells);
+
+ spin_lock_irqsave(&tc->lock, flags);
+ list_splice(&cells, &tc->deferred_cells);
+ spin_unlock_irqrestore(&tc->lock, flags);
+ return;
+ }
+
+ if (cell->holder->bi_rw & REQ_DISCARD)
+ pool->process_discard_cell(tc, cell);
+ else
+ pool->process_cell(tc, cell);
+ }
+ } while (!list_empty(&cells));
}
static void thin_get(struct thin_c *tc);