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dm thin: sort the deferred cells

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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>
This commit is contained in:
Joe Thornber 2014-10-10 16:42:10 +01:00 committed by Mike Snitzer
parent 23ca2bb6c6
commit ac4c3f34a9
1 changed files with 68 additions and 20 deletions
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88
drivers/md/dm-thin.c
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@ -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 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);
}
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);