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author | Coly Li <colyli@suse.de> | 2018-01-08 12:21:28 -0800 |
---|---|---|
committer | Jens Axboe <axboe@kernel.dk> | 2018-01-08 13:29:00 -0700 |
commit | 2831231d4c3f999d2d062b23dfbc8b0faa4bc6e0 (patch) | |
tree | dd071972cdc0362c8e577d9d9c06a106335c648e /drivers/md/bcache/btree.c | |
parent | b40503ea4f5c134b16ef405cab6c08f9343a0d06 (diff) |
bcache: reduce cache_set devices iteration by devices_max_used
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 <colyli@suse.de>
Reviewed-by: Michael Lyle <mlyle@lyle.org>
Reviewed-by: Tang Junhui <tang.junhui@zte.com.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/md/bcache/btree.c')
-rw-r--r-- | drivers/md/bcache/btree.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index 9e30713dbdb8..bf3a48aa9a9a 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -1679,7 +1679,7 @@ 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; |