bcache: Fix/revamp tracepoints
The tracepoints were reworked to be more sensible, and fixed a null
pointer deref in one of the tracepoints.
Converted some of the pr_debug()s to tracepoints - this is partly a
performance optimization; it used to be that with DEBUG or
CONFIG_DYNAMIC_DEBUG pr_debug() was an empty macro; but at some point it
was changed to an empty inline function.
Some of the pr_debug() statements had rather expensive function calls as
part of the arguments, so this code was getting run unnecessarily even
on non debug kernels - in some fast paths, too.
Signed-off-by: Kent Overstreet <koverstreet@google.com>
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index e5ff12e..6954699 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -530,10 +530,9 @@
if (KEY_CSUM(k))
bio_csum(n, k);
- pr_debug("%s", pkey(k));
+ trace_bcache_cache_insert(k);
bch_keylist_push(&op->keys);
- trace_bcache_cache_insert(n, n->bi_sector, n->bi_bdev);
n->bi_rw |= REQ_WRITE;
bch_submit_bbio(n, op->c, k, 0);
} while (n != bio);
@@ -784,11 +783,8 @@
int i;
if (s->recoverable) {
- /* The cache read failed, but we can retry from the backing
- * device.
- */
- pr_debug("recovering at sector %llu",
- (uint64_t) s->orig_bio->bi_sector);
+ /* Retry from the backing device: */
+ trace_bcache_read_retry(s->orig_bio);
s->error = 0;
bv = s->bio.bio.bi_io_vec;
@@ -806,7 +802,6 @@
/* XXX: invalidate cache */
- trace_bcache_read_retry(&s->bio.bio);
closure_bio_submit(&s->bio.bio, &s->cl, s->d);
}
@@ -899,6 +894,7 @@
struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
bch_mark_cache_accounting(s, !s->cache_miss, s->op.skip);
+ trace_bcache_read(s->orig_bio, !s->cache_miss, s->op.skip);
if (s->error)
continue_at_nobarrier(cl, request_read_error, bcache_wq);
@@ -969,7 +965,6 @@
s->cache_miss = miss;
bio_get(s->op.cache_bio);
- trace_bcache_cache_miss(s->orig_bio);
closure_bio_submit(s->op.cache_bio, &s->cl, s->d);
return ret;
@@ -1040,15 +1035,15 @@
if (should_writeback(dc, s->orig_bio))
s->writeback = true;
+ trace_bcache_write(s->orig_bio, s->writeback, s->op.skip);
+
if (!s->writeback) {
s->op.cache_bio = bio_clone_bioset(bio, GFP_NOIO,
dc->disk.bio_split);
- trace_bcache_writethrough(s->orig_bio);
closure_bio_submit(bio, cl, s->d);
} else {
s->op.cache_bio = bio;
- trace_bcache_writeback(s->orig_bio);
bch_writeback_add(dc, bio_sectors(bio));
}
out:
@@ -1058,7 +1053,6 @@
s->op.skip = true;
s->op.cache_bio = s->orig_bio;
bio_get(s->op.cache_bio);
- trace_bcache_write_skip(s->orig_bio);
if ((bio->bi_rw & REQ_DISCARD) &&
!blk_queue_discard(bdev_get_queue(dc->bdev)))
@@ -1088,9 +1082,10 @@
/* Cached devices - read & write stuff */
-int bch_get_congested(struct cache_set *c)
+unsigned bch_get_congested(struct cache_set *c)
{
int i;
+ long rand;
if (!c->congested_read_threshold_us &&
!c->congested_write_threshold_us)
@@ -1106,7 +1101,13 @@
i += CONGESTED_MAX;
- return i <= 0 ? 1 : fract_exp_two(i, 6);
+ if (i > 0)
+ i = fract_exp_two(i, 6);
+
+ rand = get_random_int();
+ i -= bitmap_weight(&rand, BITS_PER_LONG);
+
+ return i > 0 ? i : 1;
}
static void add_sequential(struct task_struct *t)
@@ -1126,10 +1127,8 @@
{
struct cache_set *c = s->op.c;
struct bio *bio = &s->bio.bio;
-
- long rand;
- int cutoff = bch_get_congested(c);
unsigned mode = cache_mode(dc, bio);
+ unsigned sectors, congested = bch_get_congested(c);
if (atomic_read(&dc->disk.detaching) ||
c->gc_stats.in_use > CUTOFF_CACHE_ADD ||
@@ -1147,17 +1146,14 @@
goto skip;
}
- if (!cutoff) {
- cutoff = dc->sequential_cutoff >> 9;
+ if (!congested && !dc->sequential_cutoff)
+ goto rescale;
- if (!cutoff)
- goto rescale;
-
- if (mode == CACHE_MODE_WRITEBACK &&
- (bio->bi_rw & REQ_WRITE) &&
- (bio->bi_rw & REQ_SYNC))
- goto rescale;
- }
+ if (!congested &&
+ mode == CACHE_MODE_WRITEBACK &&
+ (bio->bi_rw & REQ_WRITE) &&
+ (bio->bi_rw & REQ_SYNC))
+ goto rescale;
if (dc->sequential_merge) {
struct io *i;
@@ -1192,12 +1188,19 @@
add_sequential(s->task);
}
- rand = get_random_int();
- cutoff -= bitmap_weight(&rand, BITS_PER_LONG);
+ sectors = max(s->task->sequential_io,
+ s->task->sequential_io_avg) >> 9;
- if (cutoff <= (int) (max(s->task->sequential_io,
- s->task->sequential_io_avg) >> 9))
+ if (dc->sequential_cutoff &&
+ sectors >= dc->sequential_cutoff >> 9) {
+ trace_bcache_bypass_sequential(s->orig_bio);
goto skip;
+ }
+
+ if (congested && sectors >= congested) {
+ trace_bcache_bypass_congested(s->orig_bio);
+ goto skip;
+ }
rescale:
bch_rescale_priorities(c, bio_sectors(bio));