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Subject[PATCH 08/16] blkio: Dynamic cfq group creation based on cgroup tasks belongs to
Date
o Determine the cgroup IO submitting task belongs to and create the cfq
group if it does not exist already.

o Also link cfqq and associated cfq group.

o Currently all async IO is mapped to root group.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
block/cfq-iosched.c | 113 ++++++++++++++++++++++++++++++++++++++++++++++-----
1 files changed, 102 insertions(+), 11 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 4c05d45..9653caf 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -188,6 +188,10 @@ struct cfq_group {
unsigned long saved_workload_slice;
enum wl_type_t saved_workload;
enum wl_prio_t saved_serving_prio;
+ struct blkio_group blkg;
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+ struct hlist_node cfqd_node;
+#endif
};

/*
@@ -267,8 +271,13 @@ struct cfq_data {
struct cfq_queue oom_cfqq;

unsigned long last_end_sync_rq;
+
+ /* List of cfq groups being managed on this device*/
+ struct hlist_head cfqg_list;
};

+static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
+
static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
enum wl_prio_t prio,
enum wl_type_t type,
@@ -858,6 +867,91 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
cfqg->saved_workload_slice = 0;
}

+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
+{
+ if (blkg)
+ return container_of(blkg, struct cfq_group, blkg);
+ return NULL;
+}
+
+static struct cfq_group *
+cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
+{
+ struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
+ struct cfq_group *cfqg = NULL;
+ void *key = cfqd;
+ int i, j;
+
+ /* Do we need to take this reference */
+ if (!css_tryget(&blkcg->css))
+ return NULL;;
+
+ cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
+ if (cfqg || !create)
+ goto done;
+
+ cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
+ if (!cfqg)
+ goto done;
+
+ cfqg->weight = blkcg->weight;
+
+ for (i = 0; i < 2; ++i)
+ for (j = 0; j < 3; ++j)
+ cfqg->service_trees[i][j] = CFQ_RB_ROOT;
+ cfqg->service_tree_idle = CFQ_RB_ROOT;
+ RB_CLEAR_NODE(&cfqg->rb_node);
+
+ /* Add group onto cgroup list */
+ blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd);
+
+ /* Add group on cfqd list */
+ hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
+
+done:
+ css_put(&blkcg->css);
+ return cfqg;
+}
+
+/*
+ * Search for the cfq group current task belongs to. If create = 1, then also
+ * create the cfq group if it does not exist. request_queue lock must be held.
+ */
+static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
+{
+ struct cgroup *cgroup;
+ struct cfq_group *cfqg = NULL;
+
+ rcu_read_lock();
+ cgroup = task_cgroup(current, blkio_subsys_id);
+ cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create);
+ if (!cfqg && create)
+ cfqg = &cfqd->root_group;
+ rcu_read_unlock();
+ return cfqg;
+}
+
+static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
+{
+ /* Currently, all async queues are mapped to root group */
+ if (!cfq_cfqq_sync(cfqq))
+ cfqg = &cfqq->cfqd->root_group;
+
+ cfqq->cfqg = cfqg;
+}
+#else /* GROUP_IOSCHED */
+static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
+{
+ return &cfqd->root_group;
+}
+static inline void
+cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
+ cfqq->cfqg = cfqg;
+}
+
+#endif /* GROUP_IOSCHED */
+
/*
* The cfqd->service_trees holds all pending cfq_queue's that have
* requests waiting to be processed. It is sorted in the order that
@@ -1350,13 +1444,17 @@ static struct cfq_queue *__cfq_get_next_queue(struct cfq_data *cfqd)

static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
{
- struct cfq_group *cfqg = &cfqd->root_group;
+ struct cfq_group *cfqg;
struct cfq_queue *cfqq;
int i, j;

if (!cfqd->rq_queued)
return NULL;

+ cfqg = cfq_get_next_cfqg(cfqd);
+ if (!cfqg)
+ return NULL;
+
for (i = 0; i < 2; ++i) {
for (j = 0; j < 3; ++j) {
cfqq = cfq_rb_first(&cfqg->service_trees[i][j]);
@@ -2395,16 +2493,6 @@ static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
cfqq->pid = pid;
}

-static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
-{
- cfqq->cfqg = cfqg;
-}
-
-static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
-{
- return &cfqd->root_group;
-}
-
static struct cfq_queue *
cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
struct io_context *ioc, gfp_t gfp_mask)
@@ -3299,6 +3387,9 @@ static void *cfq_init_queue(struct request_queue *q)
/* Give preference to root group over other groups */
cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;

+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+ blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd);
+#endif
/*
* Not strictly needed (since RB_ROOT just clears the node and we
* zeroed cfqd on alloc), but better be safe in case someone decides
--
1.6.2.5


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