<div dir="ltr">Thanks Mikulas,<div><br></div><div>I'll test this morning.</div><div><br></div><div>- Joe</div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Oct 11, 2022 at 8:10 PM Mikulas Patocka <<a href="mailto:mpatocka@redhat.com">mpatocka@redhat.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi<br>
<br>
Here I'm sending updated patch 4 that fixes hang on discard. We must not <br>
do the optimization in dm_btree_lookup_next.<br>
<br>
Mikulas<br>
<br>
<br>
From: Mikulas Patocka <<a href="mailto:mpatocka@redhat.com" target="_blank">mpatocka@redhat.com</a>><br>
<br>
This patch reduces lock contention in btree walks. We modify the<br>
functions init_ro_wpin, exit_ro_spine and ro_step so that they use<br>
dm_bufio_lock_read/dm_bufio_get_unlocked/dm_bufio_unlock_read. If<br>
dm_bm_fast_get_block fails, we fallback to normal locking.<br>
<br>
When doing tests on pmem and fully provisioned thin volume, it improves<br>
thoughput from 286MiB/s to 442MiB/s.<br>
<br>
fio --ioengine=psync --iodepth=1 --rw=randrw --bs=4k --direct=1 --numjobs=12 --time_based --runtime=10 --group_reporting --name=/dev/vg/thin<br>
before:<br>
READ: bw=286MiB/s<br>
WRITE: bw=286MiB/s<br>
after:<br>
READ: bw=442MiB/s<br>
WRITE: bw=442MiB/s<br>
<br>
Signed-off-by: Mikulas Patocka <<a href="mailto:mpatocka@redhat.com" target="_blank">mpatocka@redhat.com</a>><br>
<br>
---<br>
drivers/md/persistent-data/dm-block-manager.c | 32 +++++++++++++++<br>
drivers/md/persistent-data/dm-block-manager.h | 6 ++<br>
drivers/md/persistent-data/dm-btree-internal.h | 4 +<br>
drivers/md/persistent-data/dm-btree-spine.c | 41 ++++++++++++++++++--<br>
drivers/md/persistent-data/dm-btree.c | 6 +-<br>
drivers/md/persistent-data/dm-transaction-manager.c | 17 ++++++++<br>
drivers/md/persistent-data/dm-transaction-manager.h | 6 ++<br>
7 files changed, 104 insertions(+), 8 deletions(-)<br>
<br>
Index: linux-2.6/drivers/md/persistent-data/dm-block-manager.c<br>
===================================================================<br>
--- linux-2.6.orig/drivers/md/persistent-data/dm-block-manager.c<br>
+++ linux-2.6/drivers/md/persistent-data/dm-block-manager.c<br>
@@ -601,6 +601,38 @@ void dm_bm_unlock(struct dm_block *b)<br>
}<br>
EXPORT_SYMBOL_GPL(dm_bm_unlock);<br>
<br>
+void dm_bm_fast_lock(struct dm_block_manager *bm)<br>
+{<br>
+ dm_bufio_lock_read(bm->bufio);<br>
+}<br>
+<br>
+void dm_bm_fast_unlock(struct dm_block_manager *bm)<br>
+{<br>
+ dm_bufio_unlock_read(bm->bufio);<br>
+}<br>
+<br>
+int dm_bm_fast_get_block(struct dm_block_manager *bm,<br>
+ dm_block_t b, struct dm_block_validator *v,<br>
+ struct dm_block **result)<br>
+{<br>
+ int r;<br>
+ struct buffer_aux *aux;<br>
+ void *p;<br>
+<br>
+ p = dm_bufio_get_unlocked(bm->bufio, b, (struct dm_buffer **) result);<br>
+ if (IS_ERR(p))<br>
+ return PTR_ERR(p);<br>
+ if (unlikely(!p))<br>
+ return -EWOULDBLOCK;<br>
+<br>
+ aux = dm_bufio_get_aux_data(to_buffer(*result));<br>
+ r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v);<br>
+ if (unlikely(r))<br>
+ return r;<br>
+<br>
+ return 0;<br>
+}<br>
+<br>
int dm_bm_flush(struct dm_block_manager *bm)<br>
{<br>
if (dm_bm_is_read_only(bm))<br>
Index: linux-2.6/drivers/md/persistent-data/dm-block-manager.h<br>
===================================================================<br>
--- linux-2.6.orig/drivers/md/persistent-data/dm-block-manager.h<br>
+++ linux-2.6/drivers/md/persistent-data/dm-block-manager.h<br>
@@ -96,6 +96,12 @@ int dm_bm_write_lock_zero(struct dm_bloc<br>
<br>
void dm_bm_unlock(struct dm_block *b);<br>
<br>
+void dm_bm_fast_lock(struct dm_block_manager *bm);<br>
+void dm_bm_fast_unlock(struct dm_block_manager *bm);<br>
+int dm_bm_fast_get_block(struct dm_block_manager *bm,<br>
+ dm_block_t b, struct dm_block_validator *v,<br>
+ struct dm_block **result);<br>
+<br>
/*<br>
* It's a common idiom to have a superblock that should be committed last.<br>
*<br>
Index: linux-2.6/drivers/md/persistent-data/dm-btree-internal.h<br>
===================================================================<br>
--- linux-2.6.orig/drivers/md/persistent-data/dm-btree-internal.h<br>
+++ linux-2.6/drivers/md/persistent-data/dm-btree-internal.h<br>
@@ -64,9 +64,11 @@ struct ro_spine {<br>
struct dm_btree_info *info;<br>
<br>
struct dm_block *node;<br>
+ bool fast_locked;<br>
+ bool fast_lock_failed;<br>
};<br>
<br>
-void init_ro_spine(struct ro_spine *s, struct dm_btree_info *info);<br>
+void init_ro_spine(struct ro_spine *s, struct dm_btree_info *info, bool disable_fast_access);<br>
void exit_ro_spine(struct ro_spine *s);<br>
int ro_step(struct ro_spine *s, dm_block_t new_child);<br>
struct btree_node *ro_node(struct ro_spine *s);<br>
Index: linux-2.6/drivers/md/persistent-data/dm-btree-spine.c<br>
===================================================================<br>
--- linux-2.6.orig/drivers/md/persistent-data/dm-btree-spine.c<br>
+++ linux-2.6/drivers/md/persistent-data/dm-btree-spine.c<br>
@@ -118,27 +118,60 @@ void unlock_block(struct dm_btree_info *<br>
dm_tm_unlock(info->tm, b);<br>
}<br>
<br>
+static void bn_fast_lock(struct dm_btree_info *info)<br>
+{<br>
+ dm_tm_fast_lock(info->tm);<br>
+}<br>
+<br>
+static void bn_fast_unlock(struct dm_btree_info *info)<br>
+{<br>
+ dm_tm_fast_unlock(info->tm);<br>
+}<br>
+<br>
+static int bn_fast_get_block(struct dm_btree_info *info, dm_block_t b,<br>
+ struct dm_block **result)<br>
+{<br>
+ return dm_tm_fast_get_block(info->tm, b, &btree_node_validator, result);<br>
+}<br>
+<br>
/*----------------------------------------------------------------*/<br>
<br>
-void init_ro_spine(struct ro_spine *s, struct dm_btree_info *info)<br>
+void init_ro_spine(struct ro_spine *s, struct dm_btree_info *info, bool disable_fast_access)<br>
{<br>
s->info = info;<br>
s->node = NULL;<br>
+ s->fast_locked = false;<br>
+ s->fast_lock_failed = disable_fast_access;<br>
}<br>
<br>
void exit_ro_spine(struct ro_spine *s)<br>
{<br>
- if (s->node)<br>
+ if (s->fast_locked)<br>
+ bn_fast_unlock(s->info);<br>
+ else if (s->node)<br>
unlock_block(s->info, s->node);<br>
}<br>
<br>
int ro_step(struct ro_spine *s, dm_block_t new_child)<br>
{<br>
if (s->node) {<br>
- unlock_block(s->info, s->node);<br>
+ if (unlikely(!s->fast_locked))<br>
+ unlock_block(s->info, s->node);<br>
s->node = NULL;<br>
}<br>
-<br>
+ if (likely(!s->fast_lock_failed)) {<br>
+ int r;<br>
+ if (!s->fast_locked) {<br>
+ bn_fast_lock(s->info);<br>
+ s->fast_locked = true;<br>
+ }<br>
+ r = bn_fast_get_block(s->info, new_child, &s->node);<br>
+ if (likely(!r))<br>
+ return 0;<br>
+ s->fast_lock_failed = true;<br>
+ s->fast_locked = false;<br>
+ bn_fast_unlock(s->info);<br>
+ }<br>
return bn_read_lock(s->info, new_child, &s->node);<br>
}<br>
<br>
Index: linux-2.6/drivers/md/persistent-data/dm-transaction-manager.c<br>
===================================================================<br>
--- linux-2.6.orig/drivers/md/persistent-data/dm-transaction-manager.c<br>
+++ linux-2.6/drivers/md/persistent-data/dm-transaction-manager.c<br>
@@ -348,6 +348,23 @@ void dm_tm_unlock(struct dm_transaction_<br>
}<br>
EXPORT_SYMBOL_GPL(dm_tm_unlock);<br>
<br>
+void dm_tm_fast_lock(struct dm_transaction_manager *tm)<br>
+{<br>
+ dm_bm_fast_lock(tm->is_clone ? tm->real->bm : tm->bm);<br>
+}<br>
+<br>
+void dm_tm_fast_unlock(struct dm_transaction_manager *tm)<br>
+{<br>
+ dm_bm_fast_unlock(tm->is_clone ? tm->real->bm : tm->bm);<br>
+}<br>
+<br>
+int dm_tm_fast_get_block(struct dm_transaction_manager *tm, dm_block_t b,<br>
+ struct dm_block_validator *v,<br>
+ struct dm_block **blk)<br>
+{<br>
+ return dm_bm_fast_get_block(tm->is_clone ? tm->real->bm : tm->bm, b, v, blk);<br>
+}<br>
+<br>
void dm_tm_inc(struct dm_transaction_manager *tm, dm_block_t b)<br>
{<br>
/*<br>
Index: linux-2.6/drivers/md/persistent-data/dm-transaction-manager.h<br>
===================================================================<br>
--- linux-2.6.orig/drivers/md/persistent-data/dm-transaction-manager.h<br>
+++ linux-2.6/drivers/md/persistent-data/dm-transaction-manager.h<br>
@@ -96,6 +96,12 @@ int dm_tm_read_lock(struct dm_transactio<br>
<br>
void dm_tm_unlock(struct dm_transaction_manager *tm, struct dm_block *b);<br>
<br>
+void dm_tm_fast_lock(struct dm_transaction_manager *tm);<br>
+void dm_tm_fast_unlock(struct dm_transaction_manager *tm);<br>
+int dm_tm_fast_get_block(struct dm_transaction_manager *tm, dm_block_t b,<br>
+ struct dm_block_validator *v,<br>
+ struct dm_block **blk);<br>
+<br>
/*<br>
* Functions for altering the reference count of a block directly.<br>
*/<br>
Index: linux-2.6/drivers/md/persistent-data/dm-btree.c<br>
===================================================================<br>
--- linux-2.6.orig/drivers/md/persistent-data/dm-btree.c<br>
+++ linux-2.6/drivers/md/persistent-data/dm-btree.c<br>
@@ -377,7 +377,7 @@ int dm_btree_lookup(struct dm_btree_info<br>
__le64 internal_value_le;<br>
struct ro_spine spine;<br>
<br>
- init_ro_spine(&spine, info);<br>
+ init_ro_spine(&spine, info, false);<br>
for (level = 0; level < info->levels; level++) {<br>
size_t size;<br>
void *value_p;<br>
@@ -472,7 +472,7 @@ int dm_btree_lookup_next(struct dm_btree<br>
__le64 internal_value_le;<br>
struct ro_spine spine;<br>
<br>
- init_ro_spine(&spine, info);<br>
+ init_ro_spine(&spine, info, true);<br>
for (level = 0; level < info->levels - 1u; level++) {<br>
r = btree_lookup_raw(&spine, root, keys[level],<br>
lower_bound, rkey,<br>
@@ -1369,7 +1369,7 @@ static int dm_btree_find_key(struct dm_b<br>
int r = 0, count = 0, level;<br>
struct ro_spine spine;<br>
<br>
- init_ro_spine(&spine, info);<br>
+ init_ro_spine(&spine, info, false);<br>
for (level = 0; level < info->levels; level++) {<br>
r = find_key(&spine, root, find_highest, result_keys + level,<br>
level == info->levels - 1 ? NULL : &root);<br>
<br>
</blockquote></div>