bcache: Better full stripe scanning

The old scanning-by-stripe code burned too much CPU, this should be
better.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 816d079..ab0b215 100644 (file)
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -237,7 +237,7 @@ struct keybuf {
 
        struct rb_root          keys;
 
-#define KEYBUF_NR              100
+#define KEYBUF_NR              500
        DECLARE_ARRAY_ALLOCATOR(struct keybuf_key, freelist, KEYBUF_NR);
 };
 
@@ -273,9 +273,10 @@ struct bcache_device {
        atomic_t                detaching;
        int                     flush_done;
 
-       uint64_t                nr_stripes;
+       unsigned                nr_stripes;
        unsigned                stripe_size;
        atomic_t                *stripe_sectors_dirty;
+       unsigned long           *full_dirty_stripes;
 
        unsigned long           sectors_dirty_last;
        long                    sectors_dirty_derivative;

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 6def7c9..5e2765a 100644 (file)
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -2378,6 +2378,7 @@ static inline int keybuf_nonoverlapping_cmp(struct keybuf_key *l,
 
 struct refill {
        struct btree_op op;
+       unsigned        nr_found;
        struct keybuf   *buf;
        struct bkey     *end;
        keybuf_pred_fn  *pred;
@@ -2414,6 +2415,8 @@ static int refill_keybuf_fn(struct btree_op *op, struct btree *b,
 
                if (RB_INSERT(&buf->keys, w, node, keybuf_cmp))
                        array_free(&buf->freelist, w);
+               else
+                       refill->nr_found++;
 
                if (array_freelist_empty(&buf->freelist))
                        ret = MAP_DONE;
@@ -2434,18 +2437,18 @@ void bch_refill_keybuf(struct cache_set *c, struct keybuf *buf,
        cond_resched();
 
        bch_btree_op_init(&refill.op, -1);
-       refill.buf = buf;
-       refill.end = end;
-       refill.pred = pred;
+       refill.nr_found = 0;
+       refill.buf      = buf;
+       refill.end      = end;
+       refill.pred     = pred;
 
        bch_btree_map_keys(&refill.op, c, &buf->last_scanned,
                           refill_keybuf_fn, MAP_END_KEY);
 
-       pr_debug("found %s keys from %llu:%llu to %llu:%llu",
-                RB_EMPTY_ROOT(&buf->keys) ? "no" :
-                array_freelist_empty(&buf->freelist) ? "some" : "a few",
-                KEY_INODE(&start), KEY_OFFSET(&start),
-                KEY_INODE(&buf->last_scanned), KEY_OFFSET(&buf->last_scanned));
+       trace_bcache_keyscan(refill.nr_found,
+                            KEY_INODE(&start), KEY_OFFSET(&start),
+                            KEY_INODE(&buf->last_scanned),
+                            KEY_OFFSET(&buf->last_scanned));
 
        spin_lock(&buf->lock);
 

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 4813ef6..43fcfe3 100644 (file)
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -738,6 +738,10 @@ static void bcache_device_free(struct bcache_device *d)
                mempool_destroy(d->unaligned_bvec);
        if (d->bio_split)
                bioset_free(d->bio_split);
+       if (is_vmalloc_addr(d->full_dirty_stripes))
+               vfree(d->full_dirty_stripes);
+       else
+               kfree(d->full_dirty_stripes);
        if (is_vmalloc_addr(d->stripe_sectors_dirty))
                vfree(d->stripe_sectors_dirty);
        else
@@ -757,8 +761,12 @@ static int bcache_device_init(struct bcache_device *d, unsigned block_size,
 
        d->nr_stripes = DIV_ROUND_UP_ULL(sectors, d->stripe_size);
 
-       if (!d->nr_stripes || d->nr_stripes > SIZE_MAX / sizeof(atomic_t))
+       if (!d->nr_stripes ||
+           d->nr_stripes > INT_MAX ||
+           d->nr_stripes > SIZE_MAX / sizeof(atomic_t)) {
+               pr_err("nr_stripes too large");
                return -ENOMEM;
+       }
 
        n = d->nr_stripes * sizeof(atomic_t);
        d->stripe_sectors_dirty = n < PAGE_SIZE << 6
@@ -767,6 +775,13 @@ static int bcache_device_init(struct bcache_device *d, unsigned block_size,
        if (!d->stripe_sectors_dirty)
                return -ENOMEM;
 
+       n = BITS_TO_LONGS(d->nr_stripes) * sizeof(unsigned long);
+       d->full_dirty_stripes = n < PAGE_SIZE << 6
+               ? kzalloc(n, GFP_KERNEL)
+               : vzalloc(n);
+       if (!d->full_dirty_stripes)
+               return -ENOMEM;
+
        if (!(d->bio_split = bioset_create(4, offsetof(struct bbio, bio))) ||
            !(d->unaligned_bvec = mempool_create_kmalloc_pool(1,
                                sizeof(struct bio_vec) * BIO_MAX_PAGES)) ||

diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index ab0f6b4..22e21dc 100644 (file)
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -292,14 +292,12 @@ void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned inode,
                                  uint64_t offset, int nr_sectors)
 {
        struct bcache_device *d = c->devices[inode];
-       unsigned stripe_offset;
-       uint64_t stripe = offset;
+       unsigned stripe_offset, stripe, sectors_dirty;
 
        if (!d)
                return;
 
-       do_div(stripe, d->stripe_size);
-
+       stripe = offset_to_stripe(d, offset);
        stripe_offset = offset & (d->stripe_size - 1);
 
        while (nr_sectors) {
@@ -309,7 +307,16 @@ void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned inode,
                if (nr_sectors < 0)
                        s = -s;
 
-               atomic_add(s, d->stripe_sectors_dirty + stripe);
+               if (stripe >= d->nr_stripes)
+                       return;
+
+               sectors_dirty = atomic_add_return(s,
+                                       d->stripe_sectors_dirty + stripe);
+               if (sectors_dirty == d->stripe_size)
+                       set_bit(stripe, d->full_dirty_stripes);
+               else
+                       clear_bit(stripe, d->full_dirty_stripes);
+
                nr_sectors -= s;
                stripe_offset = 0;
                stripe++;
@@ -321,59 +328,70 @@ static bool dirty_pred(struct keybuf *buf, struct bkey *k)
        return KEY_DIRTY(k);
 }
 
-static bool dirty_full_stripe_pred(struct keybuf *buf, struct bkey *k)
+static void refill_full_stripes(struct cached_dev *dc)
 {
-       uint64_t stripe = KEY_START(k);
-       unsigned nr_sectors = KEY_SIZE(k);
-       struct cached_dev *dc = container_of(buf, struct cached_dev,
-                                            writeback_keys);
+       struct keybuf *buf = &dc->writeback_keys;
+       unsigned start_stripe, stripe, next_stripe;
+       bool wrapped = false;
+
+       stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned));
 
-       if (!KEY_DIRTY(k))
-               return false;
+       if (stripe >= dc->disk.nr_stripes)
+               stripe = 0;
 
-       do_div(stripe, dc->disk.stripe_size);
+       start_stripe = stripe;
 
        while (1) {
-               if (atomic_read(dc->disk.stripe_sectors_dirty + stripe) ==
-                   dc->disk.stripe_size)
-                       return true;
+               stripe = find_next_bit(dc->disk.full_dirty_stripes,
+                                      dc->disk.nr_stripes, stripe);
 
-               if (nr_sectors <= dc->disk.stripe_size)
-                       return false;
+               if (stripe == dc->disk.nr_stripes)
+                       goto next;
 
-               nr_sectors -= dc->disk.stripe_size;
-               stripe++;
+               next_stripe = find_next_zero_bit(dc->disk.full_dirty_stripes,
+                                                dc->disk.nr_stripes, stripe);
+
+               buf->last_scanned = KEY(dc->disk.id,
+                                       stripe * dc->disk.stripe_size, 0);
+
+               bch_refill_keybuf(dc->disk.c, buf,
+                                 &KEY(dc->disk.id,
+                                      next_stripe * dc->disk.stripe_size, 0),
+                                 dirty_pred);
+
+               if (array_freelist_empty(&buf->freelist))
+                       return;
+
+               stripe = next_stripe;
+next:
+               if (wrapped && stripe > start_stripe)
+                       return;
+
+               if (stripe == dc->disk.nr_stripes) {
+                       stripe = 0;
+                       wrapped = true;
+               }
        }
 }
 
 static bool refill_dirty(struct cached_dev *dc)
 {
        struct keybuf *buf = &dc->writeback_keys;
-       bool searched_from_start = false;
        struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0);
+       bool searched_from_start = false;
+
+       if (dc->partial_stripes_expensive) {
+               refill_full_stripes(dc);
+               if (array_freelist_empty(&buf->freelist))
+                       return false;
+       }
 
        if (bkey_cmp(&buf->last_scanned, &end) >= 0) {
                buf->last_scanned = KEY(dc->disk.id, 0, 0);
                searched_from_start = true;
        }
 
-       if (dc->partial_stripes_expensive) {
-               uint64_t i;
-
-               for (i = 0; i < dc->disk.nr_stripes; i++)
-                       if (atomic_read(dc->disk.stripe_sectors_dirty + i) ==
-                           dc->disk.stripe_size)
-                               goto full_stripes;
-
-               goto normal_refill;
-full_stripes:
-               searched_from_start = false;    /* not searching entire btree */
-               bch_refill_keybuf(dc->disk.c, buf, &end,
-                                 dirty_full_stripe_pred);
-       } else {
-normal_refill:
-               bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
-       }
+       bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
 
        return bkey_cmp(&buf->last_scanned, &end) >= 0 && searched_from_start;
 }

diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h
index 60516bf..fe7d9d5 100644 (file)
--- a/drivers/md/bcache/writeback.h
+++ b/drivers/md/bcache/writeback.h
@@ -14,22 +14,27 @@ static inline uint64_t bcache_dev_sectors_dirty(struct bcache_device *d)
        return ret;
 }
 
-static inline bool bcache_dev_stripe_dirty(struct bcache_device *d,
+static inline unsigned offset_to_stripe(struct bcache_device *d,
+                                       uint64_t offset)
+{
+       do_div(offset, d->stripe_size);
+       return offset;
+}
+
+static inline bool bcache_dev_stripe_dirty(struct cached_dev *dc,
                                           uint64_t offset,
                                           unsigned nr_sectors)
 {
-       uint64_t stripe = offset;
-
-       do_div(stripe, d->stripe_size);
+       unsigned stripe = offset_to_stripe(&dc->disk, offset);
 
        while (1) {
-               if (atomic_read(d->stripe_sectors_dirty + stripe))
+               if (atomic_read(dc->disk.stripe_sectors_dirty + stripe))
                        return true;
 
-               if (nr_sectors <= d->stripe_size)
+               if (nr_sectors <= dc->disk.stripe_size)
                        return false;
 
-               nr_sectors -= d->stripe_size;
+               nr_sectors -= dc->disk.stripe_size;
                stripe++;
        }
 }
@@ -45,7 +50,7 @@ static inline bool should_writeback(struct cached_dev *dc, struct bio *bio,
                return false;
 
        if (dc->partial_stripes_expensive &&
-           bcache_dev_stripe_dirty(&dc->disk, bio->bi_sector,
+           bcache_dev_stripe_dirty(dc, bio->bi_sector,
                                    bio_sectors(bio)))
                return true;
 

diff --git a/include/trace/events/bcache.h b/include/trace/events/bcache.h
index 32c89b3..e2b9576 100644 (file)
--- a/include/trace/events/bcache.h
+++ b/include/trace/events/bcache.h
@@ -368,6 +368,35 @@ DEFINE_EVENT(btree_node, bcache_btree_set_root,
        TP_ARGS(b)
 );
 
+TRACE_EVENT(bcache_keyscan,
+       TP_PROTO(unsigned nr_found,
+                unsigned start_inode, uint64_t start_offset,
+                unsigned end_inode, uint64_t end_offset),
+       TP_ARGS(nr_found,
+               start_inode, start_offset,
+               end_inode, end_offset),
+
+       TP_STRUCT__entry(
+               __field(__u32,  nr_found                        )
+               __field(__u32,  start_inode                     )
+               __field(__u64,  start_offset                    )
+               __field(__u32,  end_inode                       )
+               __field(__u64,  end_offset                      )
+       ),
+
+       TP_fast_assign(
+               __entry->nr_found       = nr_found;
+               __entry->start_inode    = start_inode;
+               __entry->start_offset   = start_offset;
+               __entry->end_inode      = end_inode;
+               __entry->end_offset     = end_offset;
+       ),
+
+       TP_printk("found %u keys from %u:%llu to %u:%llu", __entry->nr_found,
+                 __entry->start_inode, __entry->start_offset,
+                 __entry->end_inode, __entry->end_offset)
+);
+
 /* Allocator */
 
 TRACE_EVENT(bcache_alloc_invalidate,