[Devel] [PATCH 06/24] io-controller: core bfq scheduler changes for hierarchical setup
Vivek Goyal
vgoyal at redhat.com
Fri Jul 24 13:27:36 PDT 2009
o Some of the core bfq scheduler changes for hiearchical groups.
Signed-off-by: Fabio Checconi <fabio at gandalf.sssup.it>
Signed-off-by: Paolo Valente <paolo.valente at unimore.it>
Signed-off-by: Nauman Rafique <nauman at google.com>
Signed-off-by: Vivek Goyal <vgoyal at redhat.com>
---
block/elevator-fq.c | 169 ++++++++++++++++++++++++++++++++++++++++++++++-----
block/elevator-fq.h | 4 +
init/Kconfig | 8 +++
3 files changed, 165 insertions(+), 16 deletions(-)
diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index e302ca0..8f8fe9a 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -38,6 +38,69 @@ static struct kmem_cache *elv_ioq_pool;
*/
#define WFQ_SERVICE_SHIFT 22
+#ifdef CONFIG_GROUP_IOSCHED
+#define for_each_entity(entity) \
+ for (; entity != NULL; entity = entity->parent)
+
+#define for_each_entity_safe(entity, parent) \
+ for (; entity && ({ parent = entity->parent; 1; }); entity = parent)
+
+
+static struct io_entity *bfq_lookup_next_entity(struct io_sched_data *sd,
+ int extract);
+
+static int bfq_update_next_active(struct io_sched_data *sd)
+{
+ struct io_group *iog;
+ struct io_entity *entity, *next_active;
+
+ if (sd->active_entity != NULL)
+ /* will update/requeue at the end of service */
+ return 0;
+
+ /*
+ * NOTE: this can be improved in may ways, such as returning
+ * 1 (and thus propagating upwards the update) only when the
+ * budget changes, or caching the bfqq that will be scheduled
+ * next from this subtree. By now we worry more about
+ * correctness than about performance...
+ */
+ next_active = bfq_lookup_next_entity(sd, 0);
+ sd->next_active = next_active;
+
+ if (next_active != NULL) {
+ iog = container_of(sd, struct io_group, sched_data);
+ entity = iog->my_entity;
+ if (entity != NULL)
+ entity->budget = next_active->budget;
+ }
+
+ return 1;
+}
+
+static inline void bfq_check_next_active(struct io_sched_data *sd,
+ struct io_entity *entity)
+{
+ BUG_ON(sd->next_active != entity);
+}
+#else /* GROUP_IOSCHED */
+#define for_each_entity(entity) \
+ for (; entity != NULL; entity = NULL)
+
+#define for_each_entity_safe(entity, parent) \
+ for (parent = NULL; entity != NULL; entity = parent)
+
+static inline int bfq_update_next_active(struct io_sched_data *sd)
+{
+ return 0;
+}
+
+static inline void bfq_check_next_active(struct io_sched_data *sd,
+ struct io_entity *entity)
+{
+}
+#endif /* GROUP_IOSCHED */
+
static inline int elv_prio_slice(struct elv_fq_data *efqd, int sync,
unsigned short prio)
{
@@ -582,8 +645,10 @@ static struct io_entity *bfq_lookup_next_entity(struct io_sched_data *sd,
entity = __bfq_lookup_next_entity(st);
if (entity != NULL) {
if (extract) {
+ bfq_check_next_active(sd, entity);
bfq_active_remove(st, entity);
sd->active_entity = entity;
+ sd->next_active = NULL;
}
break;
}
@@ -660,11 +725,8 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
if (add_front) {
struct io_entity *next_entity;
- /*
- * Determine the entity which will be dispatched next
- * Use sd->next_active once hierarchical patch is applied
- */
- next_entity = bfq_lookup_next_entity(sd, 0);
+ /* Determine the entity which will be dispatched next */
+ next_entity = sd->next_active;
if (next_entity && next_entity != entity) {
struct io_service_tree *new_st;
@@ -696,7 +758,21 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
*/
static void bfq_activate_entity(struct io_entity *entity, int add_front)
{
- __bfq_activate_entity(entity, add_front);
+ struct io_sched_data *sd;
+
+ for_each_entity(entity) {
+ __bfq_activate_entity(entity, add_front);
+
+ add_front = 0;
+ sd = entity->sched_data;
+ if (!bfq_update_next_active(sd))
+ /*
+ * No need to propagate the activation to the
+ * upper entities, as they will be updated when
+ * the active entity is rescheduled.
+ */
+ break;
+ }
}
/**
@@ -731,6 +807,8 @@ static int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
bfq_idle_remove(st, entity);
else if (entity->tree != NULL)
BUG();
+ if (was_active || sd->next_active == entity)
+ ret = bfq_update_next_active(sd);
if (!requeue || !bfq_gt(entity->finish, st->vtime))
bfq_forget_entity(st, entity);
@@ -738,6 +816,7 @@ static int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
bfq_idle_insert(st, entity);
BUG_ON(sd->active_entity == entity);
+ BUG_ON(sd->next_active == entity);
return ret;
}
@@ -749,18 +828,62 @@ static int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
*/
static void bfq_deactivate_entity(struct io_entity *entity, int requeue)
{
- __bfq_deactivate_entity(entity, requeue);
+ struct io_sched_data *sd;
+ struct io_entity *parent;
+
+ for_each_entity_safe(entity, parent) {
+ sd = entity->sched_data;
+
+ if (!__bfq_deactivate_entity(entity, requeue))
+ /*
+ * The parent entity is still backlogged, and
+ * we don't need to update it as it is still
+ * under service.
+ */
+ break;
+
+ if (sd->next_active != NULL) {
+ /*
+ * The parent entity is still backlogged and
+ * the budgets on the path towards the root
+ * need to be updated.
+ */
+ goto update;
+ }
+
+ /*
+ * If we reach there the parent is no more backlogged and
+ * we want to propagate the dequeue upwards.
+ *
+ */
+
+ requeue = 1;
+ }
+
+ return;
+
+update:
+ entity = parent;
+ for_each_entity(entity) {
+ __bfq_activate_entity(entity, 0);
+
+ sd = entity->sched_data;
+ if (!bfq_update_next_active(sd))
+ break;
+ }
}
static void entity_served(struct io_entity *entity, unsigned long served)
{
struct io_service_tree *st;
- st = io_entity_service_tree(entity);
- entity->service += served;
- BUG_ON(st->wsum == 0);
- st->vtime += bfq_delta(served, st->wsum);
- bfq_forget_idle(st);
+ for_each_entity(entity) {
+ st = io_entity_service_tree(entity);
+ entity->service += served;
+ BUG_ON(st->wsum == 0);
+ st->vtime += bfq_delta(served, st->wsum);
+ bfq_forget_idle(st);
+ }
}
/**
@@ -1068,11 +1191,25 @@ static struct io_queue *elv_get_next_ioq(struct request_queue *q, int extract)
return NULL;
sd = &efqd->root_group->sched_data;
- entity = bfq_lookup_next_entity(sd, 1);
- BUG_ON(!entity);
- if (extract)
- entity->service = 0;
+ for (; sd != NULL; sd = entity->my_sched_data) {
+ entity = bfq_lookup_next_entity(sd, 1);
+ /*
+ * entity can be null despite the fact that there are busy
+ * queues. if all the busy queues are under a group which is
+ * currently under service.
+ * So if we are just looking for next ioq while something is
+ * being served, null entity is not an error.
+ */
+ BUG_ON(!entity && extract);
+
+ if (extract)
+ entity->service = 0;
+
+ if (!entity)
+ return NULL;
+ }
+
ioq = io_entity_to_ioq(entity);
return ioq;
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index d870360..ed65a87 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -72,6 +72,7 @@ struct io_service_tree {
*/
struct io_sched_data {
struct io_entity *active_entity;
+ struct io_entity *next_active;
struct io_service_tree service_tree[IO_IOPRIO_CLASSES];
};
@@ -178,7 +179,10 @@ struct io_queue {
};
struct io_group {
+ struct io_entity entity;
struct io_sched_data sched_data;
+ struct io_entity *my_entity;
+
/*
* async queue for each priority case for RT and BE class.
* Used only for cfq.
diff --git a/init/Kconfig b/init/Kconfig
index cb2c092..fa3edd6 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -612,6 +612,14 @@ config CGROUP_MEM_RES_CTLR_SWAP
Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
size is 4096bytes, 512k per 1Gbytes of swap.
+config GROUP_IOSCHED
+ bool "Group IO Scheduler"
+ depends on CGROUPS && ELV_FAIR_QUEUING
+ default n
+ ---help---
+ This feature lets IO scheduler recognize task groups and control
+ disk bandwidth allocation to such task groups.
+
endif # CGROUPS
config MM_OWNER
--
1.6.0.6
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