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| author | Kent Overstreet <kmo@daterainc.com> | 2013-11-12 13:49:10 -0800 |
|---|---|---|
| committer | Kent Overstreet <kmo@daterainc.com> | 2014-01-08 13:05:14 -0800 |
| commit | e0a985a4b1b533311ec88c85177c45d036313f75 (patch) | |
| tree | 0433591d9d9124ef559fc54f2f71eb7027f0a56c | |
| parent | 3bdad1e40d11aad31f2322f21e943c31ef20d9da (diff) | |
| download | linux-stable-e0a985a4b1b533311ec88c85177c45d036313f75.tar.gz linux-stable-e0a985a4b1b533311ec88c85177c45d036313f75.tar.bz2 linux-stable-e0a985a4b1b533311ec88c85177c45d036313f75.zip | |
bcache: Improve bucket_prio() calculation
When deciding what order to reuse buckets we take into account both the bucket's
priority (which indicates lru order) and also the amount of live data in that
bucket. The way they were scaled together wasn't as correct as it could be...
this patch improves and documents it.
Signed-off-by: Kent Overstreet <kmo@daterainc.com>
| -rw-r--r-- | drivers/md/bcache/alloc.c | 17 | ||||
| -rw-r--r-- | drivers/md/bcache/bcache.h | 2 |
2 files changed, 16 insertions, 3 deletions
diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c index bcfd96e2121b..c0d37d082443 100644 --- a/drivers/md/bcache/alloc.c +++ b/drivers/md/bcache/alloc.c @@ -168,8 +168,21 @@ static void invalidate_one_bucket(struct cache *ca, struct bucket *b) fifo_push(&ca->free_inc, b - ca->buckets); } -#define bucket_prio(b) \ - (((unsigned) (b->prio - ca->set->min_prio)) * GC_SECTORS_USED(b)) +/* + * Determines what order we're going to reuse buckets, smallest bucket_prio() + * first: we also take into account the number of sectors of live data in that + * bucket, and in order for that multiply to make sense we have to scale bucket + * + * Thus, we scale the bucket priorities so that the bucket with the smallest + * prio is worth 1/8th of what INITIAL_PRIO is worth. + */ + +#define bucket_prio(b) \ +({ \ + unsigned min_prio = (INITIAL_PRIO - ca->set->min_prio) / 8; \ + \ + (b->prio - ca->set->min_prio + min_prio) * GC_SECTORS_USED(b); \ +}) #define bucket_max_cmp(l, r) (bucket_prio(l) < bucket_prio(r)) #define bucket_min_cmp(l, r) (bucket_prio(l) > bucket_prio(r)) diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index 93b848419665..0c707e4f4eaf 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -704,7 +704,7 @@ struct bbio { }; #define BTREE_PRIO USHRT_MAX -#define INITIAL_PRIO 32768 +#define INITIAL_PRIO 32768U #define btree_bytes(c) ((c)->btree_pages * PAGE_SIZE) #define btree_blocks(b) \ |