[Devel] Re: [PATCH 18/19] io-controller: Debug hierarchical IO scheduling

[Gui Jianfeng]

Vivek Goyal wrote:
...
> +static inline void bfq_account_for_entity_addition(struct io_entity *entity)
> +{
> +	struct io_group *iog = io_entity_to_iog(entity);
> +
> +	if (iog) {
> +		struct elv_fq_data *efqd;
> +		char path[128];
> +
> +		/*
> +		 * Keep track of how many times a group has been removed
> +		 * from active tree because it did not have any active
> +		 * backlogged ioq under it
> +		 */
> +		iog->queue++;
> +		iog->queue_start = jiffies;
> +
> +		/* Log group addition event */
> +		rcu_read_lock();
> +		efqd = rcu_dereference(iog->key);
> +		if (efqd) {
> +			io_group_path(iog, path, sizeof(path));
> +			elv_log(efqd, "add group=%s weight=%ld", path,
> +					iog->entity.weight);

Since cgroup path is already cached, why not use it. :)

Signed-off-by: Gui Jianfeng <guijianfeng at cn.fujitsu.com>
---
 block/elevator-fq.c |   12 ++++--------
 1 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index bfa79c9..1a397c3 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -183,7 +183,6 @@ static inline void bfq_account_for_entity_addition(struct io_entity *entity)
 
 	if (iog) {
 		struct elv_fq_data *efqd;
-		char path[128];
 
 		/*
 		 * Keep track of how many times a group has been removed
@@ -197,9 +196,8 @@ static inline void bfq_account_for_entity_addition(struct io_entity *entity)
 		rcu_read_lock();
 		efqd = rcu_dereference(iog->key);
 		if (efqd) {
-			io_group_path(iog, path, sizeof(path));
-			elv_log(efqd, "add group=%s weight=%ld", path,
-					iog->entity.weight);
+			elv_log(efqd, "add group=%s weight=%ld", iog->path,
+				iog->entity.weight);
 		}
 		rcu_read_unlock();
 	}
@@ -215,7 +213,6 @@ static inline void bfq_account_for_entity_deletion(struct io_entity *entity)
 
 	if (iog) {
 		struct elv_fq_data *efqd;
-		char path[128];
 
 		iog->dequeue++;
 		/* Keep a track of how long group was on active tree */
@@ -227,9 +224,8 @@ static inline void bfq_account_for_entity_deletion(struct io_entity *entity)
 		rcu_read_lock();
 		efqd = rcu_dereference(iog->key);
 		if (efqd) {
-			io_group_path(iog, path, sizeof(path));
-			elv_log(efqd, "del group=%s weight=%ld", path,
-					iog->entity.weight);
+			elv_log(efqd, "del group=%s weight=%ld", iog->path,
+				iog->entity.weight);
 		}
 		rcu_read_unlock();
 	}
-- 
1.5.4.rc3



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