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bcachefs: should_compact_all() 

This factors out a properly-documented helper for deciding when we want
to sort a btree node with MAX_BSETS bsets down to a single bset.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2022-10-28 18:56:31 -04:00
parent 46fee692ee
commit 2cb7517969
1 changed files with 24 additions and 12 deletions
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36
fs/bcachefs/btree_io.c
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@ -444,6 +444,24 @@ void bch2_btree_build_aux_trees(struct btree *b)
t == bset_tree_last(b));
}
/*
* If we have MAX_BSETS (3) bsets, should we sort them all down to just one?
*
* The first bset is going to be of similar order to the size of the node, the
* last bset is bounded by btree_write_set_buffer(), which is set to keep the
* memmove on insert from being too expensive: the middle bset should, ideally,
* be the geometric mean of the first and the last.
*
* Returns true if the middle bset is greater than that geometric mean:
*/
static inline bool should_compact_all(struct bch_fs *c, struct btree *b)
{
unsigned mid_u64s_bits =
(ilog2(btree_max_u64s(c)) + BTREE_WRITE_SET_U64s_BITS) / 2;
return bset_u64s(&b->set[1]) > 1U << mid_u64s_bits;
}
/*
* @bch_btree_init_next - initialize a new (unwritten) bset that can then be
* inserted into
@ -461,20 +479,14 @@ void bch2_btree_init_next(struct btree_trans *trans, struct btree *b)
EBUG_ON(!(b->c.lock.state.seq & 1));
BUG_ON(bset_written(b, bset(b, &b->set[1])));
BUG_ON(btree_node_just_written(b));
if (b->nsets == MAX_BSETS &&
!btree_node_write_in_flight(b)) {
unsigned log_u64s[] = {
ilog2(bset_u64s(&b->set[0])),
ilog2(bset_u64s(&b->set[1])),
ilog2(bset_u64s(&b->set[2])),
};
if (log_u64s[1] >= (log_u64s[0] + log_u64s[2]) / 2) {
bch2_btree_node_write(c, b, SIX_LOCK_write,
BTREE_WRITE_init_next_bset);
reinit_iter = true;
}
!btree_node_write_in_flight(b) &&
should_compact_all(c, b)) {
bch2_btree_node_write(c, b, SIX_LOCK_write,
BTREE_WRITE_init_next_bset);
reinit_iter = true;
}
if (b->nsets == MAX_BSETS &&