From: Tang Junhui <[email protected]> LGTM.
Reviewed-by: Tang Junhui <[email protected]> >Member devices of struct cache_set is used to reference all attached > >bcache devices to this cache set. If it is treated as array of pointers, > >size of devices[] is indicated by member nr_uuids of struct cache_set. > > > >nr_uuids is calculated in drivers/md/super.c:bch_cache_set_alloc(), > > bucket_bytes(c) / sizeof(struct uuid_entry) > >Bucket size is determined by user space tool "make-bcache", by default it > >is 1024 sectors (defined in bcache-tools/make-bcache.c:main()). So default > >nr_uuids value is 4096 from the above calculation. > > > >Every time when bcache code iterates bcache devices of a cache set, all > >the 4096 pointers are checked even only 1 bcache device is attached to the > >cache set, that's a wast of time and unncessary. > > > >This patch adds a member devices_max_used to struct cache_set. Its value > >is 1 + the maximum used index of devices[] in a cache set. When iterating > >all valid bcache devices of a cache set, use c->devices_max_used in > >for-loop may reduce a lot of useless checking. > > > >Personally, my motivation of this patch is not for performance, I use it > >in bcache debugging, which helps me to narrow down the scape to check > >valid bcached devices of a cache set. > > > >Signed-off-by: Coly Li <[email protected]> > >--- > > drivers/md/bcache/bcache.h | 1 + > > drivers/md/bcache/btree.c | 2 +- > > drivers/md/bcache/super.c | 9 ++++++--- > > drivers/md/bcache/writeback.h | 2 +- > > 4 files changed, 9 insertions(+), 5 deletions(-) > > > >diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h > >index 843877e017e1..83c569942bd0 100644 > >--- a/drivers/md/bcache/bcache.h > >+++ b/drivers/md/bcache/bcache.h > >@@ -488,6 +488,7 @@ struct cache_set { > > int caches_loaded; > > > > struct bcache_device **devices; > >+ unsigned devices_max_used; > > struct list_head cached_devs; > > uint64_t cached_dev_sectors; > > struct closure caching; > >diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c > >index 81e8dc3dbe5e..bf0d7978bc3d 100644 > >--- a/drivers/md/bcache/btree.c > >+++ b/drivers/md/bcache/btree.c > >@@ -1678,7 +1678,7 @@ static void bch_btree_gc_finish(struct cache_set *c) > > > > /* don't reclaim buckets to which writeback keys point */ > > rcu_read_lock(); > >- for (i = 0; i < c->nr_uuids; i++) { > >+ for (i = 0; i < c->devices_max_used; i++) { > > struct bcache_device *d = c->devices[i]; > > struct cached_dev *dc; > > struct keybuf_key *w, *n; > >diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c > >index b4d28928dec5..064efd869017 100644 > >--- a/drivers/md/bcache/super.c > >+++ b/drivers/md/bcache/super.c > >@@ -721,6 +721,9 @@ static void bcache_device_attach(struct bcache_device *d, >struct cache_set *c, > d->c = c; > > c->devices[id] = d; > > > >+ if (id >= c->devices_max_used) > >+ c->devices_max_used = id + 1; > >+ > > closure_get(&c->caching); > > } > > > >@@ -1261,7 +1264,7 @@ static int flash_devs_run(struct cache_set *c) > > struct uuid_entry *u; > > > > for (u = c->uuids; > >- u < c->uuids + c->nr_uuids && !ret; > >+ u < c->uuids + c->devices_max_used && !ret; > > u++) > > if (UUID_FLASH_ONLY(u)) > > ret = flash_dev_run(c, u); > >@@ -1427,7 +1430,7 @@ static void __cache_set_unregister(struct closure *cl) > > > > mutex_lock(&bch_register_lock); > > > >- for (i = 0; i < c->nr_uuids; i++) > >+ for (i = 0; i < c->devices_max_used; i++) > > if (c->devices[i]) { > > if (!UUID_FLASH_ONLY(&c->uuids[i]) && > > test_bit(CACHE_SET_UNREGISTERING, &c->flags)) { > >@@ -1490,7 +1493,7 @@ struct cache_set *bch_cache_set_alloc(struct cache_sb >*sb) > c->bucket_bits = ilog2(sb->bucket_size); > > c->block_bits = ilog2(sb->block_size); > > c->nr_uuids = bucket_bytes(c) / sizeof(struct uuid_entry); > >- > >+ c->devices_max_used = 0; > > c->btree_pages = bucket_pages(c); > > if (c->btree_pages > BTREE_MAX_PAGES) > > c->btree_pages = max_t(int, c->btree_pages / 4, > >diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h > >index a9e3ffb4b03c..1d284f3d0363 100644 > >--- a/drivers/md/bcache/writeback.h > >+++ b/drivers/md/bcache/writeback.h > >@@ -21,7 +21,7 @@ static inline uint64_t >bcache_flash_devs_sectors_dirty(struct cache_set *c) > > > mutex_lock(&bch_register_lock); > > > >- for (i = 0; i < c->nr_uuids; i++) { > >+ for (i = 0; i < c->devices_max_used; i++) { > > struct bcache_device *d = c->devices[i]; > > > > if (!d || !UUID_FLASH_ONLY(&c->uuids[i])) > >-- > >2.15.1 > Thanks, Tang Junhui
