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bcachefs: Fix CPU usage in journal read path

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In journal_entry_add(), we were repeatedly scanning the journal entries
radix tree to scan for old entries that can be freed, with O(n^2)
behaviour. This patch tweaks things to remember the previous last_seq,
so we don't have to scan for entries to free from the start.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
This commit is contained in:
Kent Overstreet 2022-04-10 16:26:34 -04:00 committed by Kent Overstreet
parent 6e811bbbc2
commit ec7ccbde6b
1 changed files with 30 additions and 43 deletions
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73
fs/bcachefs/journal_io.c
View file

@ -16,17 +16,17 @@
#include "replicas.h"
#include "trace.h"
static inline u32 journal_entry_radix_idx(struct bch_fs *c,
struct jset *j)
static inline u32 journal_entry_radix_idx(struct bch_fs *c, u64 seq)
{
return (le64_to_cpu(j->seq) - c->journal_entries_base_seq) & (~0U >> 1);
return (seq - c->journal_entries_base_seq) & (~0U >> 1);
}
static void __journal_replay_free(struct bch_fs *c,
struct journal_replay *i)
{
struct journal_replay **p =
genradix_ptr(&c->journal_entries, journal_entry_radix_idx(c, &i->j));
genradix_ptr(&c->journal_entries,
journal_entry_radix_idx(c, le64_to_cpu(i->j.seq)));
BUG_ON(*p != i);
*p = NULL;
@ -44,6 +44,7 @@ static void journal_replay_free(struct bch_fs *c, struct journal_replay *i)
struct journal_list {
struct closure cl;
u64 last_seq;
struct mutex lock;
int ret;
};
@ -64,55 +65,50 @@ static int journal_entry_add(struct bch_fs *c, struct bch_dev *ca,
struct journal_replay **_i, *i, *dup;
struct journal_ptr *ptr;
size_t bytes = vstruct_bytes(j);
u64 last_seq = 0;
u64 last_seq = !JSET_NO_FLUSH(j) ? le64_to_cpu(j->last_seq) : 0;
int ret = JOURNAL_ENTRY_ADD_OK;
/* Is this entry older than the range we need? */
if (!c->opts.read_entire_journal &&
le64_to_cpu(j->seq) < jlist->last_seq)
return JOURNAL_ENTRY_ADD_OUT_OF_RANGE;
/*
* Xarrays are indexed by a ulong, not a u64, so we can't index them by
* sequence number directly:
* Assume instead that they will all fall within the range of +-2billion
* of the filrst one we find.
* genradixes are indexed by a ulong, not a u64, so we can't index them
* by sequence number directly: Assume instead that they will all fall
* within the range of +-2billion of the filrst one we find.
*/
if (!c->journal_entries_base_seq)
c->journal_entries_base_seq = max_t(s64, 1, le64_to_cpu(j->seq) - S32_MAX);
#if 0
list_for_each_entry_reverse(i, jlist->head, list) {
if (!JSET_NO_FLUSH(&i->j)) {
last_seq = le64_to_cpu(i->j.last_seq);
break;
}
}
#endif
/* Is this entry older than the range we need? */
if (!c->opts.read_entire_journal &&
le64_to_cpu(j->seq) < last_seq) {
ret = JOURNAL_ENTRY_ADD_OUT_OF_RANGE;
goto out;
}
/* Drop entries we don't need anymore */
if (!JSET_NO_FLUSH(j) && !c->opts.read_entire_journal) {
genradix_for_each(&c->journal_entries, iter, _i) {
if (last_seq > jlist->last_seq && !c->opts.read_entire_journal) {
genradix_for_each_from(&c->journal_entries, iter, _i,
journal_entry_radix_idx(c, jlist->last_seq)) {
i = *_i;
if (!i)
if (!i || i->ignore)
continue;
if (le64_to_cpu(i->j.seq) >= le64_to_cpu(j->last_seq))
if (le64_to_cpu(i->j.seq) >= last_seq)
break;
journal_replay_free(c, i);
}
}
_i = genradix_ptr(&c->journal_entries, journal_entry_radix_idx(c, j));
dup = _i ? *_i : NULL;
jlist->last_seq = max(jlist->last_seq, last_seq);
_i = genradix_ptr_alloc(&c->journal_entries,
journal_entry_radix_idx(c, le64_to_cpu(j->seq)),
GFP_KERNEL);
if (!_i)
return -ENOMEM;
/*
* Duplicate journal entries? If so we want the one that didn't have a
* checksum error:
*/
dup = *_i;
if (dup) {
if (dup->bad) {
/* we'll replace @dup: */
@ -130,10 +126,8 @@ static int journal_entry_add(struct bch_fs *c, struct bch_dev *ca,
}
i = kvpmalloc(offsetof(struct journal_replay, j) + bytes, GFP_KERNEL);
if (!i) {
ret = -ENOMEM;
goto out;
}
if (!i)
return -ENOMEM;
i->nr_ptrs = 0;
i->bad = bad;
@ -146,14 +140,6 @@ static int journal_entry_add(struct bch_fs *c, struct bch_dev *ca,
__journal_replay_free(c, dup);
}
_i = genradix_ptr_alloc(&c->journal_entries,
journal_entry_radix_idx(c, &i->j),
GFP_KERNEL);
if (!_i) {
bch_err(c, "failed to allocate c->journal_entries entry");
ret = -ENOMEM;
goto out;
}
*_i = i;
found:
@ -1064,6 +1050,7 @@ int bch2_journal_read(struct bch_fs *c, u64 *blacklist_seq, u64 *start_seq)
closure_init_stack(&jlist.cl);
mutex_init(&jlist.lock);
jlist.last_seq = 0;
jlist.ret = 0;
for_each_member_device(ca, c, iter) {