Re: [PATCH 5/7] blk-throttle: remove asynchrnous percpu stats allocation mechanism
On Tue, Jun 23, 2015 at 10:44:11PM -0400, Tejun Heo wrote:
> Because percpu allocator couldn't do non-blocking allocations,
> blk-throttle was forced to implement an ad-hoc asynchronous allocation
> mechanism for its percpu stats for cases where blkg's (blkcg_gq's) are
> allocated from an IO path without sleepable context.
>
> Now that percpu allocator can handle gfp_mask and blkg_policy_data
> alloc / free are handled by policy methods, the ad-hoc asynchronous
> allocation mechanism can be replaced with direct allocation from
> tg_stats_alloc_fn(). Rit it out.
>
> This ensures that an active throtl_grp always has valid non-NULL
> ->stats_cpu. Remove checks on it.
This is a nice cleanup. Allocating stats memory with the help of
a worker thread was twisted.
Thanks
Vivek
>
> Signed-off-by: Tejun Heo
> Cc: Vivek Goyal
> ---
> block/blk-throttle.c | 112
> ---
> 1 file changed, 25 insertions(+), 87 deletions(-)
>
> diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> index f1dd691..3c86976 100644
> --- a/block/blk-throttle.c
> +++ b/block/blk-throttle.c
> @@ -144,9 +144,6 @@ struct throtl_grp {
>
> /* Per cpu stats pointer */
> struct tg_stats_cpu __percpu *stats_cpu;
> -
> - /* List of tgs waiting for per cpu stats memory to be allocated */
> - struct list_head stats_alloc_node;
> };
>
> struct throtl_data
> @@ -168,13 +165,6 @@ struct throtl_data
> struct work_struct dispatch_work;
> };
>
> -/* list and work item to allocate percpu group stats */
> -static DEFINE_SPINLOCK(tg_stats_alloc_lock);
> -static LIST_HEAD(tg_stats_alloc_list);
> -
> -static void tg_stats_alloc_fn(struct work_struct *);
> -static DECLARE_DELAYED_WORK(tg_stats_alloc_work, tg_stats_alloc_fn);
> -
> static void throtl_pending_timer_fn(unsigned long arg);
>
> static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
> @@ -256,53 +246,6 @@ static struct throtl_data *sq_to_td(struct
> throtl_service_queue *sq)
> } \
> } while (0)
>
> -static void tg_stats_init(struct tg_stats_cpu *tg_stats)
> -{
> - blkg_rwstat_init(_stats->service_bytes);
> - blkg_rwstat_init(_stats->serviced);
> -}
> -
> -/*
> - * Worker for allocating per cpu stat for tgs. This is scheduled on the
> - * system_wq once there are some groups on the alloc_list waiting for
> - * allocation.
> - */
> -static void tg_stats_alloc_fn(struct work_struct *work)
> -{
> - static struct tg_stats_cpu *stats_cpu; /* this fn is non-reentrant */
> - struct delayed_work *dwork = to_delayed_work(work);
> - bool empty = false;
> -
> -alloc_stats:
> - if (!stats_cpu) {
> - int cpu;
> -
> - stats_cpu = alloc_percpu(struct tg_stats_cpu);
> - if (!stats_cpu) {
> - /* allocation failed, try again after some time */
> - schedule_delayed_work(dwork, msecs_to_jiffies(10));
> - return;
> - }
> - for_each_possible_cpu(cpu)
> - tg_stats_init(per_cpu_ptr(stats_cpu, cpu));
> - }
> -
> - spin_lock_irq(_stats_alloc_lock);
> -
> - if (!list_empty(_stats_alloc_list)) {
> - struct throtl_grp *tg = list_first_entry(_stats_alloc_list,
> - struct throtl_grp,
> - stats_alloc_node);
> - swap(tg->stats_cpu, stats_cpu);
> - list_del_init(>stats_alloc_node);
> - }
> -
> - empty = list_empty(_stats_alloc_list);
> - spin_unlock_irq(_stats_alloc_lock);
> - if (!empty)
> - goto alloc_stats;
> -}
> -
> static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
> {
> INIT_LIST_HEAD(>node);
> @@ -405,7 +348,27 @@ static void throtl_service_queue_exit(struct
> throtl_service_queue *sq)
>
> static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
> {
> - return kzalloc_node(sizeof(struct throtl_grp), gfp, node);
> + struct throtl_grp *tg;
> + int cpu;
> +
> + tg = kzalloc_node(sizeof(*tg), gfp, node);
> + if (!tg)
> + return NULL;
> +
> + tg->stats_cpu = alloc_percpu_gfp(struct tg_stats_cpu, gfp);
> + if (!tg->stats_cpu) {
> + kfree(tg);
> + return NULL;
> + }
> +
> + for_each_possible_cpu(cpu) {
> + struct tg_stats_cpu *stats_cpu = per_cpu_ptr(tg->stats_cpu,
> cpu);
> +
> + blkg_rwstat_init(_cpu->service_bytes);
> + blkg_rwstat_init(_cpu->serviced);
> + }
> +
> + return >pd;
> }
>
> static void throtl_pd_init(struct blkcg_gq *blkg)
> @@ -413,7 +376,6 @@ static void throtl_pd_init(struct blkcg_gq *blkg)
> struct throtl_grp *tg = blkg_to_tg(blkg);
> struct throtl_data *td = blkg->q->td;
> struct throtl_service_queue
Re: [PATCH 5/7] blk-throttle: remove asynchrnous percpu stats allocation mechanism
On Tue, Jun 23, 2015 at 10:44:11PM -0400, Tejun Heo wrote:
Because percpu allocator couldn't do non-blocking allocations,
blk-throttle was forced to implement an ad-hoc asynchronous allocation
mechanism for its percpu stats for cases where blkg's (blkcg_gq's) are
allocated from an IO path without sleepable context.
Now that percpu allocator can handle gfp_mask and blkg_policy_data
alloc / free are handled by policy methods, the ad-hoc asynchronous
allocation mechanism can be replaced with direct allocation from
tg_stats_alloc_fn(). Rit it out.
This ensures that an active throtl_grp always has valid non-NULL
-stats_cpu. Remove checks on it.
This is a nice cleanup. Allocating stats memory with the help of
a worker thread was twisted.
Thanks
Vivek
Signed-off-by: Tejun Heo t...@kernel.org
Cc: Vivek Goyal vgo...@redhat.com
---
block/blk-throttle.c | 112
---
1 file changed, 25 insertions(+), 87 deletions(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index f1dd691..3c86976 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -144,9 +144,6 @@ struct throtl_grp {
/* Per cpu stats pointer */
struct tg_stats_cpu __percpu *stats_cpu;
-
- /* List of tgs waiting for per cpu stats memory to be allocated */
- struct list_head stats_alloc_node;
};
struct throtl_data
@@ -168,13 +165,6 @@ struct throtl_data
struct work_struct dispatch_work;
};
-/* list and work item to allocate percpu group stats */
-static DEFINE_SPINLOCK(tg_stats_alloc_lock);
-static LIST_HEAD(tg_stats_alloc_list);
-
-static void tg_stats_alloc_fn(struct work_struct *);
-static DECLARE_DELAYED_WORK(tg_stats_alloc_work, tg_stats_alloc_fn);
-
static void throtl_pending_timer_fn(unsigned long arg);
static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
@@ -256,53 +246,6 @@ static struct throtl_data *sq_to_td(struct
throtl_service_queue *sq)
} \
} while (0)
-static void tg_stats_init(struct tg_stats_cpu *tg_stats)
-{
- blkg_rwstat_init(tg_stats-service_bytes);
- blkg_rwstat_init(tg_stats-serviced);
-}
-
-/*
- * Worker for allocating per cpu stat for tgs. This is scheduled on the
- * system_wq once there are some groups on the alloc_list waiting for
- * allocation.
- */
-static void tg_stats_alloc_fn(struct work_struct *work)
-{
- static struct tg_stats_cpu *stats_cpu; /* this fn is non-reentrant */
- struct delayed_work *dwork = to_delayed_work(work);
- bool empty = false;
-
-alloc_stats:
- if (!stats_cpu) {
- int cpu;
-
- stats_cpu = alloc_percpu(struct tg_stats_cpu);
- if (!stats_cpu) {
- /* allocation failed, try again after some time */
- schedule_delayed_work(dwork, msecs_to_jiffies(10));
- return;
- }
- for_each_possible_cpu(cpu)
- tg_stats_init(per_cpu_ptr(stats_cpu, cpu));
- }
-
- spin_lock_irq(tg_stats_alloc_lock);
-
- if (!list_empty(tg_stats_alloc_list)) {
- struct throtl_grp *tg = list_first_entry(tg_stats_alloc_list,
- struct throtl_grp,
- stats_alloc_node);
- swap(tg-stats_cpu, stats_cpu);
- list_del_init(tg-stats_alloc_node);
- }
-
- empty = list_empty(tg_stats_alloc_list);
- spin_unlock_irq(tg_stats_alloc_lock);
- if (!empty)
- goto alloc_stats;
-}
-
static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
{
INIT_LIST_HEAD(qn-node);
@@ -405,7 +348,27 @@ static void throtl_service_queue_exit(struct
throtl_service_queue *sq)
static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
{
- return kzalloc_node(sizeof(struct throtl_grp), gfp, node);
+ struct throtl_grp *tg;
+ int cpu;
+
+ tg = kzalloc_node(sizeof(*tg), gfp, node);
+ if (!tg)
+ return NULL;
+
+ tg-stats_cpu = alloc_percpu_gfp(struct tg_stats_cpu, gfp);
+ if (!tg-stats_cpu) {
+ kfree(tg);
+ return NULL;
+ }
+
+ for_each_possible_cpu(cpu) {
+ struct tg_stats_cpu *stats_cpu = per_cpu_ptr(tg-stats_cpu,
cpu);
+
+ blkg_rwstat_init(stats_cpu-service_bytes);
+ blkg_rwstat_init(stats_cpu-serviced);
+ }
+
+ return tg-pd;
}
static void throtl_pd_init(struct blkcg_gq *blkg)
@@ -413,7 +376,6 @@ static void throtl_pd_init(struct blkcg_gq *blkg)
struct throtl_grp *tg = blkg_to_tg(blkg);
struct throtl_data *td = blkg-q-td;
struct throtl_service_queue *parent_sq;
- unsigned long flags;
int rw;
/*
@@ -448,16 +410,6
