[PATCH v2 1/5] blk-mq: abstract tag allocation out into scale_bitmap library
From: Omar Sandoval
Date: Wed Sep 07 2016 - 19:47:27 EST
From: Omar Sandoval <osandov@xxxxxx>
This is a generally useful data structure, so make it available to
anyone else who might want to use it. It's also a nice cleanup
separating the allocation logic from the rest of the tag handling logic.
The code is behind a new Kconfig option, CONFIG_SCALE_BITMAP, which is
only selected by CONFIG_BLOCK for now.
This should be a complete noop functionality-wise.
Signed-off-by: Omar Sandoval <osandov@xxxxxx>
---
MAINTAINERS | 1 +
block/Kconfig | 1 +
block/blk-mq-tag.c | 469 ++++++++++---------------------------------
block/blk-mq-tag.h | 37 +---
block/blk-mq.c | 113 +++--------
block/blk-mq.h | 9 -
include/linux/blk-mq.h | 9 +-
include/linux/scale_bitmap.h | 340 +++++++++++++++++++++++++++++++
lib/Kconfig | 3 +
lib/Makefile | 2 +
lib/scale_bitmap.c | 305 ++++++++++++++++++++++++++++
11 files changed, 804 insertions(+), 485 deletions(-)
create mode 100644 include/linux/scale_bitmap.h
create mode 100644 lib/scale_bitmap.c
diff --git a/MAINTAINERS b/MAINTAINERS
index db814a8..8a2c4dd 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2452,6 +2452,7 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git
S: Maintained
F: block/
F: kernel/trace/blktrace.c
+F: lib/scale_bitmap.c
BLOCK2MTD DRIVER
M: Joern Engel <joern@xxxxxxxxxxxxxxx>
diff --git a/block/Kconfig b/block/Kconfig
index 161491d..9fc09e6 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -4,6 +4,7 @@
menuconfig BLOCK
bool "Enable the block layer" if EXPERT
default y
+ select SCALE_BITMAP
help
Provide block layer support for the kernel.
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 729bac3..22eae05 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -1,12 +1,7 @@
/*
- * Fast and scalable bitmap tagging variant. Uses sparser bitmaps spread
- * over multiple cachelines to avoid ping-pong between multiple submitters
- * or submitter and completer. Uses rolling wakeups to avoid falling of
- * the scaling cliff when we run out of tags and have to start putting
- * submitters to sleep.
- *
- * Uses active queue tracking to support fairer distribution of tags
- * between multiple submitters when a shared tag map is used.
+ * Tag allocation using scalable bitmaps. Uses active queue tracking to support
+ * fairer distribution of tags between multiple submitters when a shared tag map
+ * is used.
*
* Copyright (C) 2013-2014 Jens Axboe
*/
@@ -19,40 +14,12 @@
#include "blk-mq.h"
#include "blk-mq-tag.h"
-static bool bt_has_free_tags(struct blk_mq_bitmap_tags *bt)
-{
- int i;
-
- for (i = 0; i < bt->map_nr; i++) {
- struct blk_align_bitmap *bm = &bt->map[i];
- int ret;
-
- ret = find_first_zero_bit(&bm->word, bm->depth);
- if (ret < bm->depth)
- return true;
- }
-
- return false;
-}
-
bool blk_mq_has_free_tags(struct blk_mq_tags *tags)
{
if (!tags)
return true;
- return bt_has_free_tags(&tags->bitmap_tags);
-}
-
-static inline int bt_index_inc(int index)
-{
- return (index + 1) & (BT_WAIT_QUEUES - 1);
-}
-
-static inline void bt_index_atomic_inc(atomic_t *index)
-{
- int old = atomic_read(index);
- int new = bt_index_inc(old);
- atomic_cmpxchg(index, old, new);
+ return scale_bitmap_any_bit_clear(&tags->bitmap_tags.map);
}
/*
@@ -72,29 +39,9 @@ bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
*/
void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
{
- struct blk_mq_bitmap_tags *bt;
- int i, wake_index;
-
- /*
- * Make sure all changes prior to this are visible from other CPUs.
- */
- smp_mb();
- bt = &tags->bitmap_tags;
- wake_index = atomic_read(&bt->wake_index);
- for (i = 0; i < BT_WAIT_QUEUES; i++) {
- struct bt_wait_state *bs = &bt->bs[wake_index];
-
- if (waitqueue_active(&bs->wait))
- wake_up(&bs->wait);
-
- wake_index = bt_index_inc(wake_index);
- }
-
- if (include_reserve) {
- bt = &tags->breserved_tags;
- if (waitqueue_active(&bt->bs[0].wait))
- wake_up(&bt->bs[0].wait);
- }
+ scale_bitmap_queue_wake_all(&tags->bitmap_tags);
+ if (include_reserve)
+ scale_bitmap_queue_wake_all(&tags->breserved_tags);
}
/*
@@ -118,7 +65,7 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
* and attempt to provide a fair share of the tag depth for each of them.
*/
static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
- struct blk_mq_bitmap_tags *bt)
+ struct scale_bitmap_queue *bt)
{
unsigned int depth, users;
@@ -130,7 +77,7 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
/*
* Don't try dividing an ant
*/
- if (bt->depth == 1)
+ if (bt->map.depth == 1)
return true;
users = atomic_read(&hctx->tags->active_queues);
@@ -140,127 +87,26 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
/*
* Allow at least some tags
*/
- depth = max((bt->depth + users - 1) / users, 4U);
+ depth = max((bt->map.depth + users - 1) / users, 4U);
return atomic_read(&hctx->nr_active) < depth;
}
-static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag,
- bool nowrap)
-{
- int tag, org_last_tag = last_tag;
-
- while (1) {
- tag = find_next_zero_bit(&bm->word, bm->depth, last_tag);
- if (unlikely(tag >= bm->depth)) {
- /*
- * We started with an offset, and we didn't reset the
- * offset to 0 in a failure case, so start from 0 to
- * exhaust the map.
- */
- if (org_last_tag && last_tag && !nowrap) {
- last_tag = org_last_tag = 0;
- continue;
- }
- return -1;
- }
-
- if (!test_and_set_bit(tag, &bm->word))
- break;
-
- last_tag = tag + 1;
- if (last_tag >= bm->depth - 1)
- last_tag = 0;
- }
-
- return tag;
-}
-
#define BT_ALLOC_RR(tags) (tags->alloc_policy == BLK_TAG_ALLOC_RR)
-/*
- * Straight forward bitmap tag implementation, where each bit is a tag
- * (cleared == free, and set == busy). The small twist is using per-cpu
- * last_tag caches, which blk-mq stores in the blk_mq_ctx software queue
- * contexts. This enables us to drastically limit the space searched,
- * without dirtying an extra shared cacheline like we would if we stored
- * the cache value inside the shared blk_mq_bitmap_tags structure. On top
- * of that, each word of tags is in a separate cacheline. This means that
- * multiple users will tend to stick to different cachelines, at least
- * until the map is exhausted.
- */
-static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt,
+static int __bt_get(struct blk_mq_hw_ctx *hctx, struct scale_bitmap_queue *bt,
unsigned int *tag_cache, struct blk_mq_tags *tags)
{
- unsigned int last_tag, org_last_tag;
- int index, i, tag;
-
if (!hctx_may_queue(hctx, bt))
return -1;
-
- last_tag = org_last_tag = *tag_cache;
- index = TAG_TO_INDEX(bt, last_tag);
-
- for (i = 0; i < bt->map_nr; i++) {
- tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag),
- BT_ALLOC_RR(tags));
- if (tag != -1) {
- tag += (index << bt->bits_per_word);
- goto done;
- }
-
- /*
- * Jump to next index, and reset the last tag to be the
- * first tag of that index
- */
- index++;
- last_tag = (index << bt->bits_per_word);
-
- if (index >= bt->map_nr) {
- index = 0;
- last_tag = 0;
- }
- }
-
- *tag_cache = 0;
- return -1;
-
- /*
- * Only update the cache from the allocation path, if we ended
- * up using the specific cached tag.
- */
-done:
- if (tag == org_last_tag || unlikely(BT_ALLOC_RR(tags))) {
- last_tag = tag + 1;
- if (last_tag >= bt->depth - 1)
- last_tag = 0;
-
- *tag_cache = last_tag;
- }
-
- return tag;
-}
-
-static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt,
- struct blk_mq_hw_ctx *hctx)
-{
- struct bt_wait_state *bs;
- int wait_index;
-
- if (!hctx)
- return &bt->bs[0];
-
- wait_index = atomic_read(&hctx->wait_index);
- bs = &bt->bs[wait_index];
- bt_index_atomic_inc(&hctx->wait_index);
- return bs;
+ return scale_bitmap_get(&bt->map, tag_cache, BT_ALLOC_RR(tags));
}
static int bt_get(struct blk_mq_alloc_data *data,
- struct blk_mq_bitmap_tags *bt,
- struct blk_mq_hw_ctx *hctx,
- unsigned int *last_tag, struct blk_mq_tags *tags)
+ struct scale_bitmap_queue *bt,
+ struct blk_mq_hw_ctx *hctx,
+ unsigned int *last_tag, struct blk_mq_tags *tags)
{
- struct bt_wait_state *bs;
+ struct sbq_wait_state *ws;
DEFINE_WAIT(wait);
int tag;
@@ -271,9 +117,9 @@ static int bt_get(struct blk_mq_alloc_data *data,
if (data->flags & BLK_MQ_REQ_NOWAIT)
return -1;
- bs = bt_wait_ptr(bt, hctx);
+ ws = bt_wait_ptr(bt, hctx);
do {
- prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE);
+ prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE);
tag = __bt_get(hctx, bt, last_tag, tags);
if (tag != -1)
@@ -310,11 +156,11 @@ static int bt_get(struct blk_mq_alloc_data *data,
hctx = data->hctx;
bt = &hctx->tags->bitmap_tags;
}
- finish_wait(&bs->wait, &wait);
- bs = bt_wait_ptr(bt, hctx);
+ finish_wait(&ws->wait, &wait);
+ ws = bt_wait_ptr(bt, hctx);
} while (1);
- finish_wait(&bs->wait, &wait);
+ finish_wait(&ws->wait, &wait);
return tag;
}
@@ -354,53 +200,6 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
return __blk_mq_get_tag(data);
}
-static struct bt_wait_state *bt_wake_ptr(struct blk_mq_bitmap_tags *bt)
-{
- int i, wake_index;
-
- wake_index = atomic_read(&bt->wake_index);
- for (i = 0; i < BT_WAIT_QUEUES; i++) {
- struct bt_wait_state *bs = &bt->bs[wake_index];
-
- if (waitqueue_active(&bs->wait)) {
- int o = atomic_read(&bt->wake_index);
- if (wake_index != o)
- atomic_cmpxchg(&bt->wake_index, o, wake_index);
-
- return bs;
- }
-
- wake_index = bt_index_inc(wake_index);
- }
-
- return NULL;
-}
-
-static void bt_clear_tag(struct blk_mq_bitmap_tags *bt, unsigned int tag)
-{
- const int index = TAG_TO_INDEX(bt, tag);
- struct bt_wait_state *bs;
- int wait_cnt;
-
- clear_bit(TAG_TO_BIT(bt, tag), &bt->map[index].word);
-
- /* Ensure that the wait list checks occur after clear_bit(). */
- smp_mb();
-
- bs = bt_wake_ptr(bt);
- if (!bs)
- return;
-
- wait_cnt = atomic_dec_return(&bs->wait_cnt);
- if (unlikely(wait_cnt < 0))
- wait_cnt = atomic_inc_return(&bs->wait_cnt);
- if (wait_cnt == 0) {
- atomic_add(bt->wake_cnt, &bs->wait_cnt);
- bt_index_atomic_inc(&bt->wake_index);
- wake_up(&bs->wait);
- }
-}
-
void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag,
unsigned int *last_tag)
{
@@ -410,67 +209,97 @@ void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag,
const int real_tag = tag - tags->nr_reserved_tags;
BUG_ON(real_tag >= tags->nr_tags);
- bt_clear_tag(&tags->bitmap_tags, real_tag);
+ scale_bitmap_queue_clear(&tags->bitmap_tags, real_tag);
if (likely(tags->alloc_policy == BLK_TAG_ALLOC_FIFO))
*last_tag = real_tag;
} else {
BUG_ON(tag >= tags->nr_reserved_tags);
- bt_clear_tag(&tags->breserved_tags, tag);
+ scale_bitmap_queue_clear(&tags->breserved_tags, tag);
}
}
-static void bt_for_each(struct blk_mq_hw_ctx *hctx,
- struct blk_mq_bitmap_tags *bt, unsigned int off,
- busy_iter_fn *fn, void *data, bool reserved)
+struct bt_iter_data {
+ struct blk_mq_hw_ctx *hctx;
+ busy_iter_fn *fn;
+ void *data;
+ bool reserved;
+};
+
+static bool bt_iter(struct scale_bitmap *bitmap, unsigned int bitnr, void *data)
{
+ struct bt_iter_data *iter_data = data;
+ struct blk_mq_hw_ctx *hctx = iter_data->hctx;
+ struct blk_mq_tags *tags = hctx->tags;
+ bool reserved = iter_data->reserved;
struct request *rq;
- int bit, i;
- for (i = 0; i < bt->map_nr; i++) {
- struct blk_align_bitmap *bm = &bt->map[i];
+ if (!reserved)
+ bitnr += tags->nr_reserved_tags;
+ rq = tags->rqs[bitnr];
- for (bit = find_first_bit(&bm->word, bm->depth);
- bit < bm->depth;
- bit = find_next_bit(&bm->word, bm->depth, bit + 1)) {
- rq = hctx->tags->rqs[off + bit];
- if (rq->q == hctx->queue)
- fn(hctx, rq, data, reserved);
- }
+ if (rq->q == hctx->queue)
+ iter_data->fn(hctx, rq, iter_data->data, reserved);
+ return true;
+}
- off += (1 << bt->bits_per_word);
- }
+static void bt_for_each(struct blk_mq_hw_ctx *hctx,
+ struct scale_bitmap_queue *bt, busy_iter_fn *fn,
+ void *data, bool reserved)
+{
+ struct bt_iter_data iter_data = {
+ .hctx = hctx,
+ .fn = fn,
+ .data = data,
+ .reserved = reserved,
+ };
+
+ scale_bitmap_for_each_set(&bt->map, bt_iter, &iter_data);
}
-static void bt_tags_for_each(struct blk_mq_tags *tags,
- struct blk_mq_bitmap_tags *bt, unsigned int off,
- busy_tag_iter_fn *fn, void *data, bool reserved)
+struct bt_tags_iter_data {
+ struct blk_mq_tags *tags;
+ busy_tag_iter_fn *fn;
+ void *data;
+ bool reserved;
+};
+
+static bool bt_tags_iter(struct scale_bitmap *bitmap, unsigned int bitnr,
+ void *data)
{
+ struct bt_tags_iter_data *iter_data = data;
+ struct blk_mq_tags *tags = iter_data->tags;
+ bool reserved = iter_data->reserved;
struct request *rq;
- int bit, i;
- if (!tags->rqs)
- return;
- for (i = 0; i < bt->map_nr; i++) {
- struct blk_align_bitmap *bm = &bt->map[i];
-
- for (bit = find_first_bit(&bm->word, bm->depth);
- bit < bm->depth;
- bit = find_next_bit(&bm->word, bm->depth, bit + 1)) {
- rq = tags->rqs[off + bit];
- fn(rq, data, reserved);
- }
+ if (!reserved)
+ bitnr += tags->nr_reserved_tags;
+ rq = tags->rqs[bitnr];
- off += (1 << bt->bits_per_word);
- }
+ iter_data->fn(rq, iter_data->data, reserved);
+ return true;
+}
+
+static void bt_tags_for_each(struct blk_mq_tags *tags,
+ struct scale_bitmap_queue *bt,
+ busy_tag_iter_fn *fn, void *data, bool reserved)
+{
+ struct bt_tags_iter_data iter_data = {
+ .tags = tags,
+ .fn = fn,
+ .data = data,
+ .reserved = reserved,
+ };
+
+ if (tags->rqs)
+ scale_bitmap_for_each_set(&bt->map, bt_tags_iter, &iter_data);
}
static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
busy_tag_iter_fn *fn, void *priv)
{
if (tags->nr_reserved_tags)
- bt_tags_for_each(tags, &tags->breserved_tags, 0, fn, priv, true);
- bt_tags_for_each(tags, &tags->bitmap_tags, tags->nr_reserved_tags, fn, priv,
- false);
+ bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true);
+ bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false);
}
void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
@@ -529,107 +358,21 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
continue;
if (tags->nr_reserved_tags)
- bt_for_each(hctx, &tags->breserved_tags, 0, fn, priv, true);
- bt_for_each(hctx, &tags->bitmap_tags, tags->nr_reserved_tags, fn, priv,
- false);
+ bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
+ bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
}
}
-static unsigned int bt_unused_tags(struct blk_mq_bitmap_tags *bt)
+static unsigned int bt_unused_tags(const struct scale_bitmap_queue *bt)
{
- unsigned int i, used;
-
- for (i = 0, used = 0; i < bt->map_nr; i++) {
- struct blk_align_bitmap *bm = &bt->map[i];
-
- used += bitmap_weight(&bm->word, bm->depth);
- }
-
- return bt->depth - used;
-}
-
-static void bt_update_count(struct blk_mq_bitmap_tags *bt,
- unsigned int depth)
-{
- unsigned int tags_per_word = 1U << bt->bits_per_word;
- unsigned int map_depth = depth;
-
- if (depth) {
- int i;
-
- for (i = 0; i < bt->map_nr; i++) {
- bt->map[i].depth = min(map_depth, tags_per_word);
- map_depth -= bt->map[i].depth;
- }
- }
-
- bt->wake_cnt = BT_WAIT_BATCH;
- if (bt->wake_cnt > depth / BT_WAIT_QUEUES)
- bt->wake_cnt = max(1U, depth / BT_WAIT_QUEUES);
-
- bt->depth = depth;
-}
-
-static int bt_alloc(struct blk_mq_bitmap_tags *bt, unsigned int depth,
- int node, bool reserved)
-{
- int i;
-
- bt->bits_per_word = ilog2(BITS_PER_LONG);
-
- /*
- * Depth can be zero for reserved tags, that's not a failure
- * condition.
- */
- if (depth) {
- unsigned int nr, tags_per_word;
-
- tags_per_word = (1 << bt->bits_per_word);
-
- /*
- * If the tag space is small, shrink the number of tags
- * per word so we spread over a few cachelines, at least.
- * If less than 4 tags, just forget about it, it's not
- * going to work optimally anyway.
- */
- if (depth >= 4) {
- while (tags_per_word * 4 > depth) {
- bt->bits_per_word--;
- tags_per_word = (1 << bt->bits_per_word);
- }
- }
-
- nr = ALIGN(depth, tags_per_word) / tags_per_word;
- bt->map = kzalloc_node(nr * sizeof(struct blk_align_bitmap),
- GFP_KERNEL, node);
- if (!bt->map)
- return -ENOMEM;
-
- bt->map_nr = nr;
- }
-
- bt->bs = kzalloc(BT_WAIT_QUEUES * sizeof(*bt->bs), GFP_KERNEL);
- if (!bt->bs) {
- kfree(bt->map);
- bt->map = NULL;
- return -ENOMEM;
- }
-
- bt_update_count(bt, depth);
-
- for (i = 0; i < BT_WAIT_QUEUES; i++) {
- init_waitqueue_head(&bt->bs[i].wait);
- atomic_set(&bt->bs[i].wait_cnt, bt->wake_cnt);
- }
-
- return 0;
+ return bt->map.depth - scale_bitmap_weight(&bt->map);
}
-static void bt_free(struct blk_mq_bitmap_tags *bt)
+static int bt_alloc(struct scale_bitmap_queue *bt, unsigned int depth,
+ int node)
{
- kfree(bt->map);
- kfree(bt->bs);
+ return scale_bitmap_queue_init_node(bt, depth, -1, GFP_KERNEL, node);
}
static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
@@ -639,14 +382,15 @@ static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
tags->alloc_policy = alloc_policy;
- if (bt_alloc(&tags->bitmap_tags, depth, node, false))
- goto enomem;
- if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, node, true))
- goto enomem;
+ if (bt_alloc(&tags->bitmap_tags, depth, node))
+ goto free_tags;
+ if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, node))
+ goto free_bitmap_tags;
return tags;
-enomem:
- bt_free(&tags->bitmap_tags);
+free_bitmap_tags:
+ scale_bitmap_queue_free(&tags->bitmap_tags);
+free_tags:
kfree(tags);
return NULL;
}
@@ -679,8 +423,8 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
void blk_mq_free_tags(struct blk_mq_tags *tags)
{
- bt_free(&tags->bitmap_tags);
- bt_free(&tags->breserved_tags);
+ scale_bitmap_queue_free(&tags->bitmap_tags);
+ scale_bitmap_queue_free(&tags->breserved_tags);
free_cpumask_var(tags->cpumask);
kfree(tags);
}
@@ -702,7 +446,8 @@ int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth)
* Don't need (or can't) update reserved tags here, they remain
* static and should never need resizing.
*/
- bt_update_count(&tags->bitmap_tags, tdepth);
+ scale_bitmap_queue_resize(&tags->bitmap_tags, tdepth);
+
blk_mq_tag_wakeup_all(tags, false);
return 0;
}
@@ -746,7 +491,7 @@ ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page)
page += sprintf(page, "nr_tags=%u, reserved_tags=%u, "
"bits_per_word=%u\n",
tags->nr_tags, tags->nr_reserved_tags,
- tags->bitmap_tags.bits_per_word);
+ 1U << tags->bitmap_tags.map.shift);
free = bt_unused_tags(&tags->bitmap_tags);
res = bt_unused_tags(&tags->breserved_tags);
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index d468a79..1277f24 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -3,31 +3,6 @@
#include "blk-mq.h"
-enum {
- BT_WAIT_QUEUES = 8,
- BT_WAIT_BATCH = 8,
-};
-
-struct bt_wait_state {
- atomic_t wait_cnt;
- wait_queue_head_t wait;
-} ____cacheline_aligned_in_smp;
-
-#define TAG_TO_INDEX(bt, tag) ((tag) >> (bt)->bits_per_word)
-#define TAG_TO_BIT(bt, tag) ((tag) & ((1 << (bt)->bits_per_word) - 1))
-
-struct blk_mq_bitmap_tags {
- unsigned int depth;
- unsigned int wake_cnt;
- unsigned int bits_per_word;
-
- unsigned int map_nr;
- struct blk_align_bitmap *map;
-
- atomic_t wake_index;
- struct bt_wait_state *bs;
-};
-
/*
* Tag address space map.
*/
@@ -37,8 +12,8 @@ struct blk_mq_tags {
atomic_t active_queues;
- struct blk_mq_bitmap_tags bitmap_tags;
- struct blk_mq_bitmap_tags breserved_tags;
+ struct scale_bitmap_queue bitmap_tags;
+ struct scale_bitmap_queue breserved_tags;
struct request **rqs;
struct list_head page_list;
@@ -61,6 +36,14 @@ extern void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool);
void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
void *priv);
+static inline struct sbq_wait_state *bt_wait_ptr(struct scale_bitmap_queue *bt,
+ struct blk_mq_hw_ctx *hctx)
+{
+ if (!hctx)
+ return &bt->ws[0];
+ return sbq_wait_ptr(bt, &hctx->wait_index);
+}
+
enum {
BLK_MQ_TAG_CACHE_MIN = 1,
BLK_MQ_TAG_CACHE_MAX = 64,
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 13f5a6c..7229300 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -40,42 +40,23 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx);
*/
static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx)
{
- unsigned int i;
-
- for (i = 0; i < hctx->ctx_map.size; i++)
- if (hctx->ctx_map.map[i].word)
- return true;
-
- return false;
-}
-
-static inline struct blk_align_bitmap *get_bm(struct blk_mq_hw_ctx *hctx,
- struct blk_mq_ctx *ctx)
-{
- return &hctx->ctx_map.map[ctx->index_hw / hctx->ctx_map.bits_per_word];
+ return scale_bitmap_any_bit_set(&hctx->ctx_map);
}
-#define CTX_TO_BIT(hctx, ctx) \
- ((ctx)->index_hw & ((hctx)->ctx_map.bits_per_word - 1))
-
/*
* Mark this ctx as having pending work in this hardware queue
*/
static void blk_mq_hctx_mark_pending(struct blk_mq_hw_ctx *hctx,
struct blk_mq_ctx *ctx)
{
- struct blk_align_bitmap *bm = get_bm(hctx, ctx);
-
- if (!test_bit(CTX_TO_BIT(hctx, ctx), &bm->word))
- set_bit(CTX_TO_BIT(hctx, ctx), &bm->word);
+ if (!scale_bitmap_test_bit(&hctx->ctx_map, ctx->index_hw))
+ scale_bitmap_set_bit(&hctx->ctx_map, ctx->index_hw);
}
static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
struct blk_mq_ctx *ctx)
{
- struct blk_align_bitmap *bm = get_bm(hctx, ctx);
-
- clear_bit(CTX_TO_BIT(hctx, ctx), &bm->word);
+ scale_bitmap_clear_bit(&hctx->ctx_map, ctx->index_hw);
}
void blk_mq_freeze_queue_start(struct request_queue *q)
@@ -744,38 +725,37 @@ static bool blk_mq_attempt_merge(struct request_queue *q,
return false;
}
+struct flush_busy_ctx_data {
+ struct blk_mq_hw_ctx *hctx;
+ struct list_head *list;
+};
+
+static bool flush_busy_ctx(struct scale_bitmap *bitmap, unsigned int bitnr,
+ void *data)
+{
+ struct flush_busy_ctx_data *flush_data = data;
+ struct blk_mq_hw_ctx *hctx = flush_data->hctx;
+ struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
+
+ scale_bitmap_clear_bit(bitmap, bitnr);
+ spin_lock(&ctx->lock);
+ list_splice_tail_init(&ctx->rq_list, flush_data->list);
+ spin_unlock(&ctx->lock);
+ return true;
+}
+
/*
* Process software queues that have been marked busy, splicing them
* to the for-dispatch
*/
static void flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
{
- struct blk_mq_ctx *ctx;
- int i;
-
- for (i = 0; i < hctx->ctx_map.size; i++) {
- struct blk_align_bitmap *bm = &hctx->ctx_map.map[i];
- unsigned int off, bit;
-
- if (!bm->word)
- continue;
-
- bit = 0;
- off = i * hctx->ctx_map.bits_per_word;
- do {
- bit = find_next_bit(&bm->word, bm->depth, bit);
- if (bit >= bm->depth)
- break;
-
- ctx = hctx->ctxs[bit + off];
- clear_bit(bit, &bm->word);
- spin_lock(&ctx->lock);
- list_splice_tail_init(&ctx->rq_list, list);
- spin_unlock(&ctx->lock);
+ struct flush_busy_ctx_data data = {
+ .hctx = hctx,
+ .list = list,
+ };
- bit++;
- } while (1);
- }
+ scale_bitmap_for_each_set(&hctx->ctx_map, flush_busy_ctx, &data);
}
/*
@@ -1594,32 +1574,6 @@ fail:
return NULL;
}
-static void blk_mq_free_bitmap(struct blk_mq_ctxmap *bitmap)
-{
- kfree(bitmap->map);
-}
-
-static int blk_mq_alloc_bitmap(struct blk_mq_ctxmap *bitmap, int node)
-{
- unsigned int bpw = 8, total, num_maps, i;
-
- bitmap->bits_per_word = bpw;
-
- num_maps = ALIGN(nr_cpu_ids, bpw) / bpw;
- bitmap->map = kzalloc_node(num_maps * sizeof(struct blk_align_bitmap),
- GFP_KERNEL, node);
- if (!bitmap->map)
- return -ENOMEM;
-
- total = nr_cpu_ids;
- for (i = 0; i < num_maps; i++) {
- bitmap->map[i].depth = min(total, bitmap->bits_per_word);
- total -= bitmap->map[i].depth;
- }
-
- return 0;
-}
-
/*
* 'cpu' is going away. splice any existing rq_list entries from this
* software queue to the hw queue dispatch list, and ensure that it
@@ -1685,7 +1639,7 @@ static void blk_mq_exit_hctx(struct request_queue *q,
blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
blk_free_flush_queue(hctx->fq);
- blk_mq_free_bitmap(&hctx->ctx_map);
+ scale_bitmap_free(&hctx->ctx_map);
}
static void blk_mq_exit_hw_queues(struct request_queue *q,
@@ -1745,7 +1699,8 @@ static int blk_mq_init_hctx(struct request_queue *q,
if (!hctx->ctxs)
goto unregister_cpu_notifier;
- if (blk_mq_alloc_bitmap(&hctx->ctx_map, node))
+ if (scale_bitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8),
+ GFP_KERNEL, node))
goto free_ctxs;
hctx->nr_ctx = 0;
@@ -1772,7 +1727,7 @@ static int blk_mq_init_hctx(struct request_queue *q,
if (set->ops->exit_hctx)
set->ops->exit_hctx(hctx, hctx_idx);
free_bitmap:
- blk_mq_free_bitmap(&hctx->ctx_map);
+ scale_bitmap_free(&hctx->ctx_map);
free_ctxs:
kfree(hctx->ctxs);
unregister_cpu_notifier:
@@ -1848,8 +1803,6 @@ static void blk_mq_map_swqueue(struct request_queue *q,
mutex_unlock(&q->sysfs_lock);
queue_for_each_hw_ctx(q, hctx, i) {
- struct blk_mq_ctxmap *map = &hctx->ctx_map;
-
/*
* If no software queues are mapped to this hardware queue,
* disable it and free the request entries.
@@ -1875,7 +1828,7 @@ static void blk_mq_map_swqueue(struct request_queue *q,
* This is more accurate and more efficient than looping
* over all possibly mapped software queues.
*/
- map->size = DIV_ROUND_UP(hctx->nr_ctx, map->bits_per_word);
+ scale_bitmap_resize(&hctx->ctx_map, hctx->nr_ctx);
/*
* Initialize batch roundrobin counts
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 9087b11..71831f9 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -63,15 +63,6 @@ extern void blk_mq_rq_timed_out(struct request *req, bool reserved);
void blk_mq_release(struct request_queue *q);
-/*
- * Basic implementation of sparser bitmap, allowing the user to spread
- * the bits over more cachelines.
- */
-struct blk_align_bitmap {
- unsigned long word;
- unsigned long depth;
-} ____cacheline_aligned_in_smp;
-
static inline struct blk_mq_ctx *__blk_mq_get_ctx(struct request_queue *q,
unsigned int cpu)
{
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index e43bbff..62e48dc 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -2,6 +2,7 @@
#define BLK_MQ_H
#include <linux/blkdev.h>
+#include <linux/scale_bitmap.h>
struct blk_mq_tags;
struct blk_flush_queue;
@@ -12,12 +13,6 @@ struct blk_mq_cpu_notifier {
int (*notify)(void *data, unsigned long action, unsigned int cpu);
};
-struct blk_mq_ctxmap {
- unsigned int size;
- unsigned int bits_per_word;
- struct blk_align_bitmap *map;
-};
-
struct blk_mq_hw_ctx {
struct {
spinlock_t lock;
@@ -38,7 +33,7 @@ struct blk_mq_hw_ctx {
void *driver_data;
- struct blk_mq_ctxmap ctx_map;
+ struct scale_bitmap ctx_map;
unsigned int nr_ctx;
struct blk_mq_ctx **ctxs;
diff --git a/include/linux/scale_bitmap.h b/include/linux/scale_bitmap.h
new file mode 100644
index 0000000..63f712b
--- /dev/null
+++ b/include/linux/scale_bitmap.h
@@ -0,0 +1,340 @@
+/*
+ * Fast and scalable bitmaps.
+ *
+ * Copyright (C) 2016 Facebook
+ * Copyright (C) 2013-2014 Jens Axboe
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef __LINUX_SCALE_BITMAP_H
+#define __LINUX_SCALE_BITMAP_H
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+
+/**
+ * struct scale_bitmap_word - Word in a &struct scale_bitmap.
+ */
+struct scale_bitmap_word {
+ /**
+ * @word: The bitmap word itself.
+ */
+ unsigned long word;
+
+ /**
+ * @depth: Number of bits being used in @word.
+ */
+ unsigned long depth;
+} ____cacheline_aligned_in_smp;
+
+/**
+ * struct scale_bitmap - Scalable bitmap.
+ *
+ * A &struct scale_bitmap is spread over multiple cachelines to avoid ping-pong.
+ * This trades off higher memory usage for better scalability.
+ */
+struct scale_bitmap {
+ /**
+ * @depth: Number of bits used in the whole bitmap..
+ */
+ unsigned int depth;
+
+ /**
+ * @shift: log2(number of bits used per word)
+ */
+ unsigned int shift;
+
+ /**
+ * @map_nr: Number of words (cachelines) being used for the bitmap.
+ */
+ unsigned int map_nr;
+
+ /**
+ * @map: Allocated bitmap.
+ */
+ struct scale_bitmap_word *map;
+};
+
+#define SBQ_WAIT_QUEUES 8
+#define SBQ_WAKE_BATCH 8
+
+/**
+ * struct sbq_wait_state - Wait queue in a &struct scale_bitmap.
+ */
+struct sbq_wait_state {
+ /**
+ * @wait_cnt: Number of frees remaining before we wake up.
+ */
+ atomic_t wait_cnt;
+
+ /**
+ * @wait: Wait queue.
+ */
+ wait_queue_head_t wait;
+} ____cacheline_aligned_in_smp;
+
+/**
+ * struct scale_bitmap_queue - Scalable bitmap with the added ability to wait on
+ * free bits.
+ *
+ * A &struct scale_bitmap_queue uses multiple wait queues and rolling wakeups to
+ * avoid contention on the wait queue spinlock. This ensures that we don't hit a
+ * scalability wall when we run out of free bits and have to start putting tasks
+ * to sleep.
+ */
+struct scale_bitmap_queue {
+ /**
+ * @map: Scalable bitmap.
+ */
+ struct scale_bitmap map;
+
+ /**
+ * @wake_batch: Number of bits which must be freed before we wake up any
+ * waiters.
+ */
+ unsigned int wake_batch;
+
+ /**
+ * @wake_index: Next wait queue in @ws to wake up.
+ */
+ atomic_t wake_index;
+
+ /**
+ * @ws: Wait queues.
+ */
+ struct sbq_wait_state *ws;
+};
+
+/**
+ * scale_bitmap_init_node() - Initialize a &struct scale_bitmap on a specific
+ * memory node.
+ * @bitmap: Bitmap to initialize.
+ * @depth: Number of bits to allocate.
+ * @shift: Use 2^@shift bits per word in the bitmap; if a negative number if
+ * given, a good default is chosen.
+ * @flags: Allocation flags.
+ * @node: Memory node to allocate on.
+ *
+ * Return: Zero on success or negative errno on failure.
+ */
+int scale_bitmap_init_node(struct scale_bitmap *bitmap, unsigned int depth,
+ int shift, gfp_t flags, int node);
+
+/**
+ * scale_bitmap_free() - Free memory used by a &struct scale_bitmap.
+ * @bitmap: Bitmap to free.
+ */
+static inline void scale_bitmap_free(struct scale_bitmap *bitmap)
+{
+ kfree(bitmap->map);
+ bitmap->map = NULL;
+}
+
+/**
+ * scale_bitmap_resize() - Resize a &struct scale_bitmap.
+ * @bitmap: Bitmap to resize.
+ * @depth: New number of bits to resize to.
+ *
+ * Doesn't reallocate anything. It's up to the caller to ensure that the new
+ * depth doesn't exceed the depth that the bitmap was initialized with.
+ */
+void scale_bitmap_resize(struct scale_bitmap *bitmap, unsigned int depth);
+
+/**
+ * scale_bitmap_get() - Try to allocate a free bit from a &struct scale_bitmap.
+ * @bitmap: Bitmap to allocate from.
+ * @alloc_hint: Cache of last successfully allocated bit. This should be per-cpu
+ * for best results, which allows multiple users to stick to
+ * different cachelines until the map is exhausted.
+ * @round_robin: If true, be stricter about allocation order; always allocate
+ * starting from the last allocated bit. This is less efficient
+ * than the default behavior (false).
+ *
+ * Return: Non-negative allocated bit number if successful, -1 otherwise.
+ */
+int scale_bitmap_get(struct scale_bitmap *bitmap, unsigned int *alloc_hint,
+ bool round_robin);
+
+/**
+ * scale_bitmap_any_bit_set() - Check for a set bit in a &struct scale_bitmap.
+ * @bitmap: Bitmap to check.
+ *
+ * Return: true if any bit in the bitmap is set, false otherwise.
+ */
+bool scale_bitmap_any_bit_set(const struct scale_bitmap *bitmap);
+
+/**
+ * scale_bitmap_any_bit_clear() - Check for an unset bit in a &struct
+ * scale_bitmap.
+ * @bitmap: Bitmap to check.
+ *
+ * Return: true if any bit in the bitmap is clear, false otherwise.
+ */
+bool scale_bitmap_any_bit_clear(const struct scale_bitmap *bitmap);
+
+typedef bool (*sb_for_each_fn)(struct scale_bitmap *, unsigned int, void *);
+
+/**
+ * scale_bitmap_for_each_set() - Iterate over each set bit in a &struct
+ * scale_bitmap.
+ * @bitmap: Bitmap to iterate over.
+ * @fn: Callback. Should return true to continue or false to break early.
+ * @data: Pointer to pass to callback.
+ *
+ * This is inline even though it's non-trivial so that the function calls to the
+ * callback will hopefully get optimized away.
+ */
+static inline void scale_bitmap_for_each_set(struct scale_bitmap *bitmap,
+ sb_for_each_fn fn, void *data)
+{
+ unsigned int i;
+
+ for (i = 0; i < bitmap->map_nr; i++) {
+ struct scale_bitmap_word *word = &bitmap->map[i];
+ unsigned int off, nr;
+
+ if (!word->word)
+ continue;
+
+ nr = 0;
+ off = i << bitmap->shift;
+ while (1) {
+ nr = find_next_bit(&word->word, word->depth, nr);
+ if (nr >= word->depth)
+ break;
+
+ if (!fn(bitmap, off + nr, data))
+ return;
+
+ nr++;
+ }
+ }
+}
+
+#define SB_NR_TO_INDEX(bitmap, bitnr) ((bitnr) >> (bitmap)->shift)
+#define SB_NR_TO_BIT(bitmap, bitnr) ((bitnr) & ((1U << (bitmap)->shift) - 1U))
+
+static inline unsigned long *__scale_bitmap_word(struct scale_bitmap *bitmap,
+ unsigned int bitnr)
+{
+ return &bitmap->map[SB_NR_TO_INDEX(bitmap, bitnr)].word;
+}
+
+/* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */
+
+static inline void scale_bitmap_set_bit(struct scale_bitmap *bitmap,
+ unsigned int bitnr)
+{
+ set_bit(SB_NR_TO_BIT(bitmap, bitnr),
+ __scale_bitmap_word(bitmap, bitnr));
+}
+
+static inline void scale_bitmap_clear_bit(struct scale_bitmap *bitmap,
+ unsigned int bitnr)
+{
+ clear_bit(SB_NR_TO_BIT(bitmap, bitnr),
+ __scale_bitmap_word(bitmap, bitnr));
+}
+
+static inline int scale_bitmap_test_bit(struct scale_bitmap *bitmap,
+ unsigned int bitnr)
+{
+ return test_bit(SB_NR_TO_BIT(bitmap, bitnr),
+ __scale_bitmap_word(bitmap, bitnr));
+}
+
+unsigned int scale_bitmap_weight(const struct scale_bitmap *bitmap);
+
+/**
+ * scale_bitmap_queue_init_node() - Initialize a &struct scale_bitmap_queue on a
+ * specific memory node.
+ * @sbq: Bitmap queue to initialize.
+ * @depth: See scale_bitmap_init_node().
+ * @shift: See scale_bitmap_init_node().
+ * @flags: Allocation flags.
+ * @node: Memory node to allocate on.
+ *
+ * Return: Zero on success or negative errno on failure.
+ */
+int scale_bitmap_queue_init_node(struct scale_bitmap_queue *sbq,
+ unsigned int depth, int shift, gfp_t flags,
+ int node);
+
+/**
+ * scale_bitmap_queue_free() - Free memory used by a &struct scale_bitmap_queue.
+ *
+ * @sbq: Bitmap queue to free.
+ */
+static inline void scale_bitmap_queue_free(struct scale_bitmap_queue *sbq)
+{
+ kfree(sbq->ws);
+ scale_bitmap_free(&sbq->map);
+}
+
+/**
+ * scale_bitmap_queue_resize() - Resize a &struct scale_bitmap_queue.
+ * @sbq: Bitmap queue to resize.
+ * @depth: New number of bits to resize to.
+ *
+ * Like scale_bitmap_resize(), this doesn't reallocate anything. It has to do
+ * some extra work on the &struct scale_bitmap_queue, so it's not safe to just
+ * resize the underlying &struct scale_bitmap.
+ */
+void scale_bitmap_queue_resize(struct scale_bitmap_queue *sbq,
+ unsigned int depth);
+
+/**
+ * scale_bitmap_queue_clear() - Free an allocated bit and wake up waiters on a
+ * &struct scale_bitmap_queue.
+ * @sbq: Bitmap to free from.
+ * @nr: Bit number to free.
+ */
+void scale_bitmap_queue_clear(struct scale_bitmap_queue *sbq, unsigned int nr);
+
+static inline int sbq_index_inc(int index)
+{
+ return (index + 1) & (SBQ_WAIT_QUEUES - 1);
+}
+
+static inline void sbq_index_atomic_inc(atomic_t *index)
+{
+ int old = atomic_read(index);
+ int new = sbq_index_inc(old);
+ atomic_cmpxchg(index, old, new);
+}
+
+/**
+ * sbq_wait_ptr() - Get the next wait queue to use for a &struct
+ * scale_bitmap_queue.
+ * @sbq: Bitmap queue to wait on.
+ * @wait_index: A counter per "user" of @sbq.
+ */
+static inline struct sbq_wait_state *sbq_wait_ptr(struct scale_bitmap_queue *sbq,
+ atomic_t *wait_index)
+{
+ struct sbq_wait_state *ws;
+
+ ws = &sbq->ws[atomic_read(wait_index)];
+ sbq_index_atomic_inc(wait_index);
+ return ws;
+}
+
+/**
+ * scale_bitmap_queue_wake_all() - Wake up everything waiting on a &struct
+ * scale_bitmap_queue.
+ * @sbq: Bitmap queue to wake up.
+ */
+void scale_bitmap_queue_wake_all(struct scale_bitmap_queue *sbq);
+
+#endif /* __LINUX_SCALE_BITMAP_H */
diff --git a/lib/Kconfig b/lib/Kconfig
index d79909d..5a7830c 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -550,4 +550,7 @@ config STACKDEPOT
bool
select STACKTRACE
+config SCALE_BITMAP
+ bool
+
endmenu
diff --git a/lib/Makefile b/lib/Makefile
index 5dc77a8..74a9e62 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -227,3 +227,5 @@ obj-$(CONFIG_UCS2_STRING) += ucs2_string.o
obj-$(CONFIG_UBSAN) += ubsan.o
UBSAN_SANITIZE_ubsan.o := n
+
+obj-$(CONFIG_SCALE_BITMAP) += scale_bitmap.o
diff --git a/lib/scale_bitmap.c b/lib/scale_bitmap.c
new file mode 100644
index 0000000..4d47c19
--- /dev/null
+++ b/lib/scale_bitmap.c
@@ -0,0 +1,305 @@
+/*
+ * Copyright (C) 2016 Facebook
+ * Copyright (C) 2013-2014 Jens Axboe
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <linux/scale_bitmap.h>
+
+int scale_bitmap_init_node(struct scale_bitmap *bitmap, unsigned int depth,
+ int shift, gfp_t flags, int node)
+{
+ unsigned int bits_per_word;
+ unsigned int i;
+
+ if (shift < 0) {
+ shift = ilog2(BITS_PER_LONG);
+ /*
+ * If the bitmap is small, shrink the number of bits per word so
+ * we spread over a few cachelines, at least. If less than 4
+ * bits, just forget about it, it's not going to work optimally
+ * anyway.
+ */
+ if (depth >= 4) {
+ while ((4U << shift) > depth)
+ shift--;
+ }
+ }
+ bits_per_word = 1U << shift;
+ if (bits_per_word > BITS_PER_LONG)
+ return -EINVAL;
+
+ bitmap->shift = shift;
+ bitmap->depth = depth;
+ bitmap->map_nr = DIV_ROUND_UP(bitmap->depth, bits_per_word);
+
+ if (depth == 0) {
+ bitmap->map = NULL;
+ return 0;
+ }
+
+ bitmap->map = kzalloc_node(bitmap->map_nr * sizeof(*bitmap->map), flags,
+ node);
+ if (!bitmap->map)
+ return -ENOMEM;
+
+ for (i = 0; i < bitmap->map_nr; i++) {
+ bitmap->map[i].depth = min(depth, bits_per_word);
+ depth -= bitmap->map[i].depth;
+ }
+ return 0;
+}
+EXPORT_SYMBOL_GPL(scale_bitmap_init_node);
+
+void scale_bitmap_resize(struct scale_bitmap *bitmap, unsigned int depth)
+{
+ unsigned int bits_per_word = 1U << bitmap->shift;
+ unsigned int i;
+
+ bitmap->depth = depth;
+ bitmap->map_nr = DIV_ROUND_UP(bitmap->depth, bits_per_word);
+
+ for (i = 0; i < bitmap->map_nr; i++) {
+ bitmap->map[i].depth = min(depth, bits_per_word);
+ depth -= bitmap->map[i].depth;
+ }
+}
+EXPORT_SYMBOL_GPL(scale_bitmap_resize);
+
+static int __scale_bitmap_get_word(struct scale_bitmap_word *word,
+ unsigned int hint, bool wrap)
+{
+ unsigned int orig_hint = hint;
+ int nr;
+
+ while (1) {
+ nr = find_next_zero_bit(&word->word, word->depth, hint);
+ if (unlikely(nr >= word->depth)) {
+ /*
+ * We started with an offset, and we didn't reset the
+ * offset to 0 in a failure case, so start from 0 to
+ * exhaust the map.
+ */
+ if (orig_hint && hint && wrap) {
+ hint = orig_hint = 0;
+ continue;
+ }
+ return -1;
+ }
+
+ if (!test_and_set_bit(nr, &word->word))
+ break;
+
+ hint = nr + 1;
+ if (hint >= word->depth - 1)
+ hint = 0;
+ }
+
+ return nr;
+}
+
+int scale_bitmap_get(struct scale_bitmap *bitmap, unsigned int *alloc_hint,
+ bool round_robin)
+{
+ unsigned int hint, orig_hint;
+ unsigned int i, index;
+ int nr;
+
+ hint = orig_hint = *alloc_hint;
+ index = SB_NR_TO_INDEX(bitmap, hint);
+
+ for (i = 0; i < bitmap->map_nr; i++) {
+ nr = __scale_bitmap_get_word(&bitmap->map[index],
+ SB_NR_TO_BIT(bitmap, hint),
+ !round_robin);
+ if (nr != -1) {
+ nr += index << bitmap->shift;
+ goto done;
+ }
+
+ /* Jump to next index. */
+ index++;
+ hint = index << bitmap->shift;
+
+ if (index >= bitmap->map_nr) {
+ index = 0;
+ hint = 0;
+ }
+ }
+
+ *alloc_hint = 0;
+ return -1;
+
+done:
+ /* Only update the cache if we used the cached value. */
+ if (nr == orig_hint || unlikely(round_robin)) {
+ hint = nr + 1;
+ if (hint >= bitmap->depth - 1)
+ hint = 0;
+ *alloc_hint = hint;
+ }
+
+ return nr;
+}
+EXPORT_SYMBOL_GPL(scale_bitmap_get);
+
+bool scale_bitmap_any_bit_set(const struct scale_bitmap *bitmap)
+{
+ unsigned int i;
+
+ for (i = 0; i < bitmap->map_nr; i++) {
+ if (bitmap->map[i].word)
+ return true;
+ }
+ return false;
+}
+EXPORT_SYMBOL_GPL(scale_bitmap_any_bit_set);
+
+bool scale_bitmap_any_bit_clear(const struct scale_bitmap *bitmap)
+{
+ unsigned int i;
+
+ for (i = 0; i < bitmap->map_nr; i++) {
+ const struct scale_bitmap_word *word = &bitmap->map[i];
+ unsigned long ret;
+
+ ret = find_first_zero_bit(&word->word, word->depth);
+ if (ret < word->depth)
+ return true;
+ }
+ return false;
+}
+EXPORT_SYMBOL_GPL(scale_bitmap_any_bit_clear);
+
+unsigned int scale_bitmap_weight(const struct scale_bitmap *bitmap)
+{
+ unsigned int i, weight;
+
+ for (i = 0; i < bitmap->map_nr; i++) {
+ const struct scale_bitmap_word *word = &bitmap->map[i];
+
+ weight += bitmap_weight(&word->word, word->depth);
+ }
+ return weight;
+}
+EXPORT_SYMBOL_GPL(scale_bitmap_weight);
+
+int scale_bitmap_queue_init_node(struct scale_bitmap_queue *sbq,
+ unsigned int depth, int shift, gfp_t flags,
+ int node)
+{
+ int ret;
+ int i;
+
+ ret = scale_bitmap_init_node(&sbq->map, depth, shift, flags, node);
+ if (ret)
+ return ret;
+
+ sbq->wake_batch = SBQ_WAKE_BATCH;
+ if (sbq->wake_batch > depth / SBQ_WAIT_QUEUES)
+ sbq->wake_batch = max(1U, depth / SBQ_WAIT_QUEUES);
+
+ atomic_set(&sbq->wake_index, 0);
+
+ sbq->ws = kzalloc(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags);
+ if (!sbq->ws) {
+ scale_bitmap_free(&sbq->map);
+ return -ENOMEM;
+ }
+
+ for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
+ init_waitqueue_head(&sbq->ws[i].wait);
+ atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch);
+ }
+ return 0;
+}
+EXPORT_SYMBOL_GPL(scale_bitmap_queue_init_node);
+
+void scale_bitmap_queue_resize(struct scale_bitmap_queue *sbq,
+ unsigned int depth)
+{
+ scale_bitmap_resize(&sbq->map, depth);
+
+ sbq->wake_batch = SBQ_WAKE_BATCH;
+ if (sbq->wake_batch > depth / SBQ_WAIT_QUEUES)
+ sbq->wake_batch = max(1U, depth / SBQ_WAIT_QUEUES);
+}
+EXPORT_SYMBOL_GPL(scale_bitmap_queue_resize);
+
+static struct sbq_wait_state *sbq_wake_ptr(struct scale_bitmap_queue *sbq)
+{
+ int i, wake_index;
+
+ wake_index = atomic_read(&sbq->wake_index);
+ for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
+ struct sbq_wait_state *ws = &sbq->ws[wake_index];
+
+ if (waitqueue_active(&ws->wait)) {
+ int o = atomic_read(&sbq->wake_index);
+
+ if (wake_index != o)
+ atomic_cmpxchg(&sbq->wake_index, o, wake_index);
+ return ws;
+ }
+
+ wake_index = sbq_index_inc(wake_index);
+ }
+
+ return NULL;
+}
+
+void scale_bitmap_queue_clear(struct scale_bitmap_queue *sbq, unsigned int nr)
+{
+ struct sbq_wait_state *ws;
+ int wait_cnt;
+
+ scale_bitmap_clear_bit(&sbq->map, nr);
+
+ /* Ensure that the wait list checks occur after clear_bit(). */
+ smp_mb();
+
+ ws = sbq_wake_ptr(sbq);
+ if (!ws)
+ return;
+
+ wait_cnt = atomic_dec_return(&ws->wait_cnt);
+ if (unlikely(wait_cnt < 0))
+ wait_cnt = atomic_inc_return(&ws->wait_cnt);
+ if (wait_cnt == 0) {
+ atomic_add(sbq->wake_batch, &ws->wait_cnt);
+ sbq_index_atomic_inc(&sbq->wake_index);
+ wake_up(&ws->wait);
+ }
+}
+EXPORT_SYMBOL_GPL(scale_bitmap_queue_clear);
+
+void scale_bitmap_queue_wake_all(struct scale_bitmap_queue *sbq)
+{
+ int i, wake_index;
+
+ /*
+ * Make sure all changes prior to this are visible from other CPUs.
+ */
+ smp_mb();
+ wake_index = atomic_read(&sbq->wake_index);
+ for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
+ struct sbq_wait_state *ws = &sbq->ws[wake_index];
+
+ if (waitqueue_active(&ws->wait))
+ wake_up(&ws->wait);
+
+ wake_index = sbq_index_inc(wake_index);
+ }
+}
+EXPORT_SYMBOL_GPL(scale_bitmap_queue_wake_all);
--
2.9.3