[dm-devel] [dm-5.19 PATCH 10/21] dm: conditionally enable branching for less used features
Mike Snitzer
snitzer at kernel.org
Mon Apr 18 02:27:22 UTC 2022
Use jump_labels to further reduce cost of unlikely branches for zoned
block devices, dm-stats and swap_bios throttling.
Signed-off-by: Mike Snitzer <snitzer at kernel.org>
---
drivers/md/dm-core.h | 5 ++++
drivers/md/dm-stats.c | 3 +++
drivers/md/dm-table.c | 5 ++++
drivers/md/dm.c | 63 ++++++++++++++++++++++++++++++++-------------------
4 files changed, 53 insertions(+), 23 deletions(-)
diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
index 41d6511dc7cf..8ba99eaa0872 100644
--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h
@@ -13,6 +13,7 @@
#include <linux/ktime.h>
#include <linux/blk-mq.h>
#include <linux/blk-crypto-profile.h>
+#include <linux/jump_label.h>
#include <trace/events/block.h>
@@ -154,6 +155,10 @@ static inline struct dm_stats *dm_get_stats(struct mapped_device *md)
return &md->stats;
}
+DECLARE_STATIC_KEY_FALSE(stats_enabled);
+DECLARE_STATIC_KEY_FALSE(swap_bios_enabled);
+DECLARE_STATIC_KEY_FALSE(zoned_enabled);
+
static inline bool dm_emulate_zone_append(struct mapped_device *md)
{
if (blk_queue_is_zoned(md->queue))
diff --git a/drivers/md/dm-stats.c b/drivers/md/dm-stats.c
index 0e039a8c0bf2..86e0697330e8 100644
--- a/drivers/md/dm-stats.c
+++ b/drivers/md/dm-stats.c
@@ -396,6 +396,9 @@ static int dm_stats_create(struct dm_stats *stats, sector_t start, sector_t end,
dm_stats_recalc_precise_timestamps(stats);
+ if (!static_key_enabled(&stats_enabled.key))
+ static_branch_enable(&stats_enabled);
+
mutex_unlock(&stats->mutex);
resume_callback(md);
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index ffd97cb6d1c1..a9d2fc5d9ad9 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -719,6 +719,9 @@ int dm_table_add_target(struct dm_table *t, const char *type,
DMWARN("%s: %s: ignoring discards_supported because num_discard_bios is zero.",
dm_device_name(t->md), type);
+ if (tgt->limit_swap_bios && !static_key_enabled(&swap_bios_enabled.key))
+ static_branch_enable(&swap_bios_enabled);
+
return 0;
bad:
@@ -2051,6 +2054,8 @@ int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
r = dm_set_zones_restrictions(t, q);
if (r)
return r;
+ if (!static_key_enabled(&zoned_enabled.key))
+ static_branch_enable(&zoned_enabled);
}
dm_update_crypto_profile(q, t);
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 073b41ce7a30..3359b55daa99 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -71,6 +71,10 @@ void dm_issue_global_event(void)
wake_up(&dm_global_eventq);
}
+DEFINE_STATIC_KEY_FALSE(stats_enabled);
+DEFINE_STATIC_KEY_FALSE(swap_bios_enabled);
+DEFINE_STATIC_KEY_FALSE(zoned_enabled);
+
/*
* One of these is allocated (on-stack) per original bio.
*/
@@ -516,7 +520,8 @@ static void dm_io_acct(bool end, struct mapped_device *md, struct bio *bio,
else
bio_end_io_acct(bio, start_time);
- if (unlikely(dm_stats_used(&md->stats)))
+ if (static_branch_unlikely(&stats_enabled) &&
+ unlikely(dm_stats_used(&md->stats)))
dm_stats_account_io(&md->stats, bio_data_dir(bio),
bio->bi_iter.bi_sector, bio_sectors(bio),
end, start_time, stats_aux);
@@ -586,7 +591,8 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
io->start_time = jiffies;
io->flags = 0;
- dm_stats_record_start(&md->stats, &io->stats_aux);
+ if (static_branch_unlikely(&stats_enabled))
+ dm_stats_record_start(&md->stats, &io->stats_aux);
return io;
}
@@ -1013,21 +1019,25 @@ static void clone_endio(struct bio *bio)
disable_write_zeroes(md);
}
- if (unlikely(blk_queue_is_zoned(q)))
+ if (static_branch_unlikely(&zoned_enabled) &&
+ unlikely(blk_queue_is_zoned(q)))
dm_zone_endio(io, bio);
if (endio) {
int r = endio(ti, bio, &error);
switch (r) {
case DM_ENDIO_REQUEUE:
- /*
- * Requeuing writes to a sequential zone of a zoned
- * target will break the sequential write pattern:
- * fail such IO.
- */
- if (WARN_ON_ONCE(dm_is_zone_write(md, bio)))
- error = BLK_STS_IOERR;
- else
+ if (static_branch_unlikely(&zoned_enabled)) {
+ /*
+ * Requeuing writes to a sequential zone of a zoned
+ * target will break the sequential write pattern:
+ * fail such IO.
+ */
+ if (WARN_ON_ONCE(dm_is_zone_write(md, bio)))
+ error = BLK_STS_IOERR;
+ else
+ error = BLK_STS_DM_REQUEUE;
+ } else
error = BLK_STS_DM_REQUEUE;
fallthrough;
case DM_ENDIO_DONE:
@@ -1041,7 +1051,8 @@ static void clone_endio(struct bio *bio)
}
}
- if (unlikely(swap_bios_limit(ti, bio)))
+ if (static_branch_unlikely(&swap_bios_enabled) &&
+ unlikely(swap_bios_limit(ti, bio)))
up(&md->swap_bios_semaphore);
free_tio(bio);
@@ -1296,21 +1307,25 @@ static void __map_bio(struct bio *clone)
dm_io_inc_pending(io);
tio->old_sector = clone->bi_iter.bi_sector;
- if (unlikely(swap_bios_limit(ti, clone))) {
+ if (static_branch_unlikely(&swap_bios_enabled) &&
+ unlikely(swap_bios_limit(ti, clone))) {
int latch = get_swap_bios();
if (unlikely(latch != md->swap_bios))
__set_swap_bios_limit(md, latch);
down(&md->swap_bios_semaphore);
}
- /*
- * Check if the IO needs a special mapping due to zone append emulation
- * on zoned target. In this case, dm_zone_map_bio() calls the target
- * map operation.
- */
- if (unlikely(dm_emulate_zone_append(md)))
- r = dm_zone_map_bio(tio);
- else
+ if (static_branch_unlikely(&zoned_enabled)) {
+ /*
+ * Check if the IO needs a special mapping due to zone append
+ * emulation on zoned target. In this case, dm_zone_map_bio()
+ * calls the target map operation.
+ */
+ if (unlikely(dm_emulate_zone_append(md)))
+ r = dm_zone_map_bio(tio);
+ else
+ r = ti->type->map(ti, clone);
+ } else
r = ti->type->map(ti, clone);
switch (r) {
@@ -1330,7 +1345,8 @@ static void __map_bio(struct bio *clone)
break;
case DM_MAPIO_KILL:
case DM_MAPIO_REQUEUE:
- if (unlikely(swap_bios_limit(ti, clone)))
+ if (static_branch_unlikely(&swap_bios_enabled) &&
+ unlikely(swap_bios_limit(ti, clone)))
up(&md->swap_bios_semaphore);
free_tio(clone);
if (r == DM_MAPIO_KILL)
@@ -1566,7 +1582,8 @@ static void init_clone_info(struct clone_info *ci, struct mapped_device *md,
ci->sector_count = bio_sectors(bio);
/* Shouldn't happen but sector_count was being set to 0 so... */
- if (WARN_ON_ONCE(op_is_zone_mgmt(bio_op(bio)) && ci->sector_count))
+ if (static_branch_unlikely(&zoned_enabled) &&
+ WARN_ON_ONCE(op_is_zone_mgmt(bio_op(bio)) && ci->sector_count))
ci->sector_count = 0;
}
--
2.15.0
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