[PATCH] blk-throttle: don't check whether or not lower limit is valid if CONFIG_BLK_DEV_THROTTLING_LOW is off

[PATCH] blk-throttle: don't check whether or not lower limit is valid if CONFIG_BLK_DEV_THROTTLING_LOW is off

[Yu Kuai]

blk_throtl_update_limit_valid() will search for descendants to see if
'LIMIT_LOW' of bps/iops and READ/WRITE is nonzero. However, they're always
zero if CONFIG_BLK_DEV_THROTTLING_LOW is not set, furthermore, a lot of
time will be wasted to iterate descendants.

Thus do nothing in blk_throtl_update_limit_valid() in such situation.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
 block/blk-throttle.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index b771c4299982..d52cac9f3a7c 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -587,6 +587,7 @@ static void throtl_pd_online(struct blkg_policy_data *pd)
 	tg_update_has_rules(tg);
 }
 
+#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
 static void blk_throtl_update_limit_valid(struct throtl_data *td)
 {
 	struct cgroup_subsys_state *pos_css;
@@ -607,6 +608,11 @@ static void blk_throtl_update_limit_valid(struct throtl_data *td)
 
 	td->limit_valid[LIMIT_LOW] = low_valid;
 }
+#else
+static inline void blk_throtl_update_limit_valid(struct throtl_data *td)
+{
+}
+#endif
 
 static void throtl_upgrade_state(struct throtl_data *td);
 static void throtl_pd_offline(struct blkg_policy_data *pd)
-- 
2.25.4

Re: [PATCH] blk-throttle: don't check whether or not lower limit is valid if CONFIG_BLK_DEV_THROTTLING_LOW is off

[Tejun Heo]

On Thu, Nov 26, 2020 at 11:18:34AM +0800, Yu Kuai wrote:
> blk_throtl_update_limit_valid() will search for descendants to see if
> 'LIMIT_LOW' of bps/iops and READ/WRITE is nonzero. However, they're always
> zero if CONFIG_BLK_DEV_THROTTLING_LOW is not set, furthermore, a lot of
> time will be wasted to iterate descendants.
> 
> Thus do nothing in blk_throtl_update_limit_valid() in such situation.
> 
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

Re: [PATCH] blk-throttle: don't check whether or not lower limit is valid if CONFIG_BLK_DEV_THROTTLING_LOW is off

[Jens Axboe]

On 11/25/20 8:18 PM, Yu Kuai wrote:
> blk_throtl_update_limit_valid() will search for descendants to see if
> 'LIMIT_LOW' of bps/iops and READ/WRITE is nonzero. However, they're always
> zero if CONFIG_BLK_DEV_THROTTLING_LOW is not set, furthermore, a lot of
> time will be wasted to iterate descendants.
> 
> Thus do nothing in blk_throtl_update_limit_valid() in such situation.

Applied, thanks.

-- 
Jens Axboe