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bcache: finish incremental GC

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In GC thread, we record the latest GC key in gc_done, which is expected
to be used for incremental GC, but in currently code, we didn't realize
it. When GC runs, front side IO would be blocked until the GC over, it
would be a long time if there is a lot of btree nodes.

This patch realizes incremental GC, the main ideal is that, when there
are front side I/Os, after GC some nodes (100), we stop GC, release locker
of the btree node, and go to process the front side I/Os for some times
(100 ms), then go back to GC again.

By this patch, when we doing GC, I/Os are not blocked all the time, and
there is no obvious I/Os zero jump problem any more.

Patch v2: Rename some variables and macros name as Coly suggested.

Signed-off-by: Tang Junhui <tang.junhui@zte.com.cn>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tang Junhui 2018-07-26 12:17:34 +08:00 committed by Jens Axboe
parent 99a27d59bd
commit 5c25c4fc74
3 changed files with 21 additions and 1 deletions
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5
drivers/md/bcache/bcache.h
View file

@ -474,6 +474,7 @@ struct cache {
struct gc_stat {
size_t nodes;
size_t nodes_pre;
size_t key_bytes;
size_t nkeys;
@ -603,6 +604,10 @@ struct cache_set {
* rescale; when it hits 0 we rescale all the bucket priorities.
*/
atomic_t rescale;
/*
* used for GC, identify if any front side I/Os is inflight
*/
atomic_t search_inflight;
/*
* When we invalidate buckets, we use both the priority and the amount
* of good data to determine which buckets to reuse first - to weight

14
drivers/md/bcache/btree.c
View file

@ -90,6 +90,8 @@
#define MAX_NEED_GC 64
#define MAX_SAVE_PRIO 72
#define MIN_GC_NODES 100
#define GC_SLEEP_MS 100
#define PTR_DIRTY_BIT (((uint64_t) 1 << 36))
@ -1585,6 +1587,13 @@ static int btree_gc_recurse(struct btree *b, struct btree_op *op,
memmove(r + 1, r, sizeof(r[0]) * (GC_MERGE_NODES - 1));
r->b = NULL;
if (atomic_read(&b->c->search_inflight) &&
gc->nodes >= gc->nodes_pre + MIN_GC_NODES) {
gc->nodes_pre = gc->nodes;
ret = -EAGAIN;
break;
}
if (need_resched()) {
ret = -EAGAIN;
break;
@ -1753,7 +1762,10 @@ static void bch_btree_gc(struct cache_set *c)
closure_sync(&writes);
cond_resched();
if (ret && ret != -EAGAIN)
if (ret == -EAGAIN)
schedule_timeout_interruptible(msecs_to_jiffies
(GC_SLEEP_MS));
else if (ret)
pr_warn("gc failed!");
} while (ret && !test_bit(CACHE_SET_IO_DISABLE, &c->flags));

3
drivers/md/bcache/request.c
View file

@ -701,6 +701,8 @@ static void search_free(struct closure *cl)
{
struct search *s = container_of(cl, struct search, cl);
atomic_dec(&s->d->c->search_inflight);
if (s->iop.bio)
bio_put(s->iop.bio);
@ -718,6 +720,7 @@ static inline struct search *search_alloc(struct bio *bio,
closure_init(&s->cl, NULL);
do_bio_hook(s, bio, request_endio);
atomic_inc(&d->c->search_inflight);
s->orig_bio = bio;
s->cache_miss = NULL;