bcachefs: Ensure journal reclaim runs when btree key cache is too dirty

Ensuring the key cache isn't too dirty is critical for ensuring that the
shrinker can reclaim memory.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/btree_key_cache.c b/fs/bcachefs/btree_key_cache.c
index 836bb23..99e0385 100644 (file)
--- a/fs/bcachefs/btree_key_cache.c
+++ b/fs/bcachefs/btree_key_cache.c
@@ -461,6 +461,7 @@ bool bch2_btree_insert_key_cached(struct btree_trans *trans,
 {
        struct bch_fs *c = trans->c;
        struct bkey_cached *ck = (void *) iter->l[0].b;
+       bool kick_reclaim = false;
 
        BUG_ON(insert->u64s > ck->u64s);
 
@@ -485,11 +486,18 @@ bool bch2_btree_insert_key_cached(struct btree_trans *trans,
 
                set_bit(BKEY_CACHED_DIRTY, &ck->flags);
                c->btree_key_cache.nr_dirty++;
+
+               if (bch2_nr_btree_keys_need_flush(c))
+                       kick_reclaim = true;
+
                mutex_unlock(&c->btree_key_cache.lock);
        }
 
        bch2_journal_pin_update(&c->journal, trans->journal_res.seq,
                                &ck->journal, btree_key_cache_journal_flush);
+
+       if (kick_reclaim)
+               mod_delayed_work(c->journal_reclaim_wq, &c->journal.reclaim_work, 0);
        return true;
 }
 

diff --git a/fs/bcachefs/btree_key_cache.h b/fs/bcachefs/btree_key_cache.h
index e64a8e9..7723a21 100644 (file)
--- a/fs/bcachefs/btree_key_cache.h
+++ b/fs/bcachefs/btree_key_cache.h
@@ -1,6 +1,15 @@
 #ifndef _BCACHEFS_BTREE_KEY_CACHE_H
 #define _BCACHEFS_BTREE_KEY_CACHE_H
 
+static inline size_t bch2_nr_btree_keys_need_flush(struct bch_fs *c)
+{
+       size_t nr_dirty = READ_ONCE(c->btree_key_cache.nr_dirty);
+       size_t nr_keys = READ_ONCE(c->btree_key_cache.nr_dirty);
+       size_t max_dirty = 1024 + (nr_keys * 3) / 4;
+
+       return max_t(ssize_t, 0, nr_dirty - max_dirty);
+}
+
 struct bkey_cached *
 bch2_btree_key_cache_find(struct bch_fs *, enum btree_id, struct bpos);
 

diff --git a/fs/bcachefs/journal_reclaim.c b/fs/bcachefs/journal_reclaim.c
index 1cd9c11..7f8ab13 100644 (file)
--- a/fs/bcachefs/journal_reclaim.c
+++ b/fs/bcachefs/journal_reclaim.c
@@ -1,11 +1,13 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include "bcachefs.h"
+#include "btree_key_cache.h"
 #include "journal.h"
 #include "journal_io.h"
 #include "journal_reclaim.h"
 #include "replicas.h"
 #include "super.h"
+#include "trace.h"
 
 /* Free space calculations: */
 
@@ -432,7 +434,6 @@ journal_get_next_pin(struct journal *j, u64 max_seq, u64 *seq)
                list_move(&ret->list, &pin_list->flushed);
                BUG_ON(j->flush_in_progress);
                j->flush_in_progress = ret;
-               j->last_flushed = jiffies;
        }
 
        spin_unlock(&j->lock);
@@ -441,17 +442,24 @@ journal_get_next_pin(struct journal *j, u64 max_seq, u64 *seq)
 }
 
 /* returns true if we did work */
-static bool journal_flush_pins(struct journal *j, u64 seq_to_flush,
-                              unsigned min_nr)
+static u64 journal_flush_pins(struct journal *j, u64 seq_to_flush,
+                             unsigned min_nr)
 {
        struct journal_entry_pin *pin;
-       bool ret = false;
-       u64 seq;
+       u64 seq, ret = 0;
 
        lockdep_assert_held(&j->reclaim_lock);
 
-       while ((pin = journal_get_next_pin(j, min_nr
-                               ? U64_MAX : seq_to_flush, &seq))) {
+       while (1) {
+               cond_resched();
+
+               j->last_flushed = jiffies;
+
+               pin = journal_get_next_pin(j, min_nr
+                               ? U64_MAX : seq_to_flush, &seq);
+               if (!pin)
+                       break;
+
                if (min_nr)
                        min_nr--;
 
@@ -460,7 +468,7 @@ static bool journal_flush_pins(struct journal *j, u64 seq_to_flush,
                BUG_ON(j->flush_in_progress != pin);
                j->flush_in_progress = NULL;
                wake_up(&j->pin_flush_wait);
-               ret = true;
+               ret++;
        }
 
        return ret;
@@ -527,8 +535,8 @@ static u64 journal_seq_to_flush(struct journal *j)
 void bch2_journal_reclaim(struct journal *j)
 {
        struct bch_fs *c = container_of(j, struct bch_fs, journal);
-       unsigned min_nr = 0;
-       u64 seq_to_flush = 0;
+       u64 seq_to_flush, nr_flushed = 0;
+       size_t min_nr;
 
        lockdep_assert_held(&j->reclaim_lock);
 
@@ -549,12 +557,25 @@ void bch2_journal_reclaim(struct journal *j)
                if (j->prereserved.reserved * 2 > j->prereserved.remaining)
                        min_nr = 1;
 
-               if ((atomic_read(&c->btree_cache.dirty) * 4 >
-                    c->btree_cache.used  * 3) ||
-                   (c->btree_key_cache.nr_dirty * 4 >
-                    c->btree_key_cache.nr_keys))
+               if (atomic_read(&c->btree_cache.dirty) * 4 >
+                   c->btree_cache.used  * 3)
                        min_nr = 1;
-       } while (journal_flush_pins(j, seq_to_flush, min_nr));
+
+               min_nr = max(min_nr, bch2_nr_btree_keys_need_flush(c));
+
+               trace_journal_reclaim_start(c,
+                               min_nr,
+                               j->prereserved.reserved,
+                               j->prereserved.remaining,
+                               atomic_read(&c->btree_cache.dirty),
+                               c->btree_cache.used,
+                               c->btree_key_cache.nr_dirty,
+                               c->btree_key_cache.nr_keys);
+
+               nr_flushed += journal_flush_pins(j, seq_to_flush, min_nr);
+       } while (min_nr);
+
+       trace_journal_reclaim_finish(c, nr_flushed);
 
        if (!bch2_journal_error(j))
                queue_delayed_work(c->journal_reclaim_wq, &j->reclaim_work,
@@ -582,7 +603,7 @@ static int journal_flush_done(struct journal *j, u64 seq_to_flush,
 
        mutex_lock(&j->reclaim_lock);
 
-       *did_work = journal_flush_pins(j, seq_to_flush, 0);
+       *did_work = journal_flush_pins(j, seq_to_flush, 0) != 0;
 
        spin_lock(&j->lock);
        /*

diff --git a/fs/bcachefs/trace.h b/fs/bcachefs/trace.h
index 09653c7..2afc09a 100644 (file)
--- a/fs/bcachefs/trace.h
+++ b/fs/bcachefs/trace.h
@@ -121,6 +121,65 @@ DEFINE_EVENT(bio, journal_write,
        TP_ARGS(bio)
 );
 
+TRACE_EVENT(journal_reclaim_start,
+       TP_PROTO(struct bch_fs *c, u64 min_nr,
+                u64 prereserved, u64 prereserved_total,
+                u64 btree_cache_dirty, u64 btree_cache_total,
+                u64 btree_key_cache_dirty, u64 btree_key_cache_total),
+       TP_ARGS(c, min_nr, prereserved, prereserved_total,
+               btree_cache_dirty, btree_cache_total,
+               btree_key_cache_dirty, btree_key_cache_total),
+
+       TP_STRUCT__entry(
+               __array(char,           uuid,   16              )
+               __field(u64,            min_nr                  )
+               __field(u64,            prereserved             )
+               __field(u64,            prereserved_total       )
+               __field(u64,            btree_cache_dirty       )
+               __field(u64,            btree_cache_total       )
+               __field(u64,            btree_key_cache_dirty   )
+               __field(u64,            btree_key_cache_total   )
+       ),
+
+       TP_fast_assign(
+               memcpy(__entry->uuid, c->sb.user_uuid.b, 16);
+               __entry->min_nr                 = min_nr;
+               __entry->prereserved            = prereserved;
+               __entry->prereserved_total      = prereserved_total;
+               __entry->btree_cache_dirty      = btree_cache_dirty;
+               __entry->btree_cache_total      = btree_cache_total;
+               __entry->btree_key_cache_dirty  = btree_key_cache_dirty;
+               __entry->btree_key_cache_total  = btree_key_cache_total;
+       ),
+
+       TP_printk("%pU min %llu prereserved %llu/%llu btree cache %llu/%llu key cache %llu/%llu",
+                 __entry->uuid,
+                 __entry->min_nr,
+                 __entry->prereserved,
+                 __entry->prereserved_total,
+                 __entry->btree_cache_dirty,
+                 __entry->btree_cache_total,
+                 __entry->btree_key_cache_dirty,
+                 __entry->btree_key_cache_total)
+);
+
+TRACE_EVENT(journal_reclaim_finish,
+       TP_PROTO(struct bch_fs *c, u64 nr_flushed),
+       TP_ARGS(c, nr_flushed),
+
+       TP_STRUCT__entry(
+               __array(char,           uuid,   16 )
+               __field(u64,            nr_flushed )
+       ),
+
+       TP_fast_assign(
+               memcpy(__entry->uuid, c->sb.user_uuid.b, 16);
+               __entry->nr_flushed = nr_flushed;
+       ),
+
+       TP_printk("%pU flushed %llu", __entry->uuid, __entry->nr_flushed)
+);
+
 /* bset.c: */
 
 DEFINE_EVENT(bpos, bkey_pack_pos_fail,