On 2018/4/12 2:38 PM, tang.junhui@xxxxxxxxxx wrote:
> From: Tang Junhui <tang.junhui@xxxxxxxxxx>
>
> Since no new bucket can be allocated during GC, and front side I/Os would
> run out of all the buckets, so notify allocator to pack the free_inc queue
> full of buckets before GC, then we could have enough buckets for front side
> I/Os during GC period.
>
> Signed-off-by: Tang Junhui <tang.junhui@xxxxxxxxxx>
Hi Junhui,
This method is complicated IMHO. Why not in bch_allocator_thread()
simple call wake_up_gc(ca->set) after invalidate_buckets() ?
Thanks.
Coly Li
> ---
> drivers/md/bcache/alloc.c | 11 +++++++-
> drivers/md/bcache/bcache.h | 2 ++
> drivers/md/bcache/btree.c | 69 ++++++++++++++++++++++++++++++++++++++++++++--
> drivers/md/bcache/btree.h | 4 +++
> 4 files changed, 83 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
> index a0cc1bc..85020cc 100644
> --- a/drivers/md/bcache/alloc.c
> +++ b/drivers/md/bcache/alloc.c
> @@ -323,7 +323,8 @@ static int bch_allocator_thread(void *arg)
> * possibly issue discards to them, then we add the bucket to
> * the free list:
> */
> - while (!fifo_empty(&ca->free_inc)) {
> + while (!fifo_empty(&ca->free_inc) &&
> + ca->prepare_gc != GC_PREPARING) {
> long bucket;
>
> fifo_pop(&ca->free_inc, bucket);
> @@ -353,6 +354,14 @@ static int bch_allocator_thread(void *arg)
> invalidate_buckets(ca);
>
> /*
> + * Let GC continue
> + */
> + if (ca->prepare_gc == GC_PREPARING) {
> + ca->prepare_gc = GC_PREPARED;
> + wake_up_gc(ca->set);
> + }
> +
> + /*
> * Now, we write their new gens to disk so we can start writing
> * new stuff to them:
> */
> diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
> index ab4c9ca..61a6ff2 100644
> --- a/drivers/md/bcache/bcache.h
> +++ b/drivers/md/bcache/bcache.h
> @@ -428,6 +428,8 @@ struct cache {
> * cpu
> */
> unsigned invalidate_needs_gc;
> + /* used to notify allocator to prepare GC*/
> + unsigned int prepare_gc;
>
> bool discard; /* Get rid of? */
>
> diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
> index 10f967e..aba0700 100644
> --- a/drivers/md/bcache/btree.c
> +++ b/drivers/md/bcache/btree.c
> @@ -1805,6 +1805,46 @@ static void bch_btree_gc(struct cache_set *c)
> bch_moving_gc(c);
> }
>
> +static bool cache_gc_prepare_none(struct cache_set *c)
> +{
> + struct cache *ca;
> + unsigned int i;
> +
> + for_each_cache(ca, c, i)
> + if (ca->prepare_gc != GC_PREPARE_NONE)
> + return false;
> + return true;
> +}
> +
> +static bool cache_gc_prepare_ok(struct cache_set *c)
> +{
> + struct cache *ca;
> + unsigned int i;
> +
> + for_each_cache(ca, c, i)
> + if (ca->prepare_gc != GC_PREPARED)
> + return false;
> + return true;
> +}
> +
> +static void set_cache_gc_prepare_none(struct cache_set *c)
> +{
> + struct cache *ca;
> + unsigned int i;
> +
> + for_each_cache(ca, c, i)
> + ca->prepare_gc = GC_PREPARE_NONE;
> +}
> +
> +static void set_cache_gc_preparing(struct cache_set *c)
> +{
> + struct cache *ca;
> + unsigned int i;
> +
> + for_each_cache(ca, c, i)
> + ca->prepare_gc = GC_PREPARING;
> +}
> +
> static bool gc_should_run(struct cache_set *c)
> {
> struct cache *ca;
> @@ -1814,8 +1854,33 @@ static bool gc_should_run(struct cache_set *c)
> if (ca->invalidate_needs_gc)
> return true;
>
> - if (atomic_read(&c->sectors_to_gc) < 0)
> - return true;
> + if (atomic_read(&c->sectors_to_gc) < 0) {
> + mutex_lock(&c->bucket_lock);
> + if (cache_gc_prepare_none(c)) {
> + /*
> + * notify allocator thread to prepare for GC
> + */
> + set_cache_gc_preparing(c);
> + mutex_unlock(&c->bucket_lock);
> + pr_info("gc preparing");
> + return false;
> + } else if (cache_gc_prepare_ok(c)) {
> + /*
> + * alloc thread finished preparing,
> + * and continue to GC
> + */
> + set_cache_gc_prepare_none(c);
> + mutex_unlock(&c->bucket_lock);
> + pr_info("gc prepared ok");
> + return true;
> + } else {
> + /*
> + * waitting allocator finishing prepareing
> + */
> + mutex_unlock(&c->bucket_lock);
> + return false;
> + }
> + }
>
> return false;
> }
> diff --git a/drivers/md/bcache/btree.h b/drivers/md/bcache/btree.h
> index d211e2c..e60bd7a 100644
> --- a/drivers/md/bcache/btree.h
> +++ b/drivers/md/bcache/btree.h
> @@ -102,6 +102,10 @@
> #include "bset.h"
> #include "debug.h"
>
> +#define GC_PREPARE_NONE 0
> +#define GC_PREPARING 1
> +#define GC_PREPARED 2
> +
> struct btree_write {
> atomic_t *journal;
>
>
