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Subject[PATCH 02/21] blkio: Introduce the notion of cfq groups
Date
o This patch introduce the notion of cfq groups. Soon we will can have multiple
groups of different weights in the system.

o Various service trees (prioclass and workload type trees), will become per
cfq group. So hierarchy looks as follows.

cfq_groups
|
workload type
|
cfq queue
o When an scheduling decision has to be taken, first we select the cfq group
then workload with-in the group and then cfq queue with-in the workload
type.

o This patch just makes various workload service tree per cfq group and
introduce the function to be able to choose a group for scheduling.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
block/cfq-iosched.c | 109 +++++++++++++++++++++++++++++++++++---------------
1 files changed, 76 insertions(+), 33 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 9adfa48..3baa3f4 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -132,6 +132,7 @@ struct cfq_queue {

struct cfq_rb_root *service_tree;
struct cfq_queue *new_cfqq;
+ struct cfq_group *cfqg;
};

/*
@@ -153,25 +154,30 @@ enum wl_type_t {
SYNC_WORKLOAD = 2
};

+/* This is per cgroup per device grouping structure */
+struct cfq_group {
+ /*
+ * rr lists of queues with requests, onle rr for each priority class.
+ * Counts are embedded in the cfq_rb_root
+ */
+ struct cfq_rb_root service_trees[2][3];
+ struct cfq_rb_root service_tree_idle;
+};

/*
* Per block device queue structure
*/
struct cfq_data {
struct request_queue *queue;
+ struct cfq_group root_group;

/*
- * rr lists of queues with requests, onle rr for each priority class.
- * Counts are embedded in the cfq_rb_root
- */
- struct cfq_rb_root service_trees[2][3];
- struct cfq_rb_root service_tree_idle;
- /*
* The priority currently being served
*/
enum wl_prio_t serving_prio;
enum wl_type_t serving_type;
unsigned long workload_expires;
+ struct cfq_group *serving_group;
bool noidle_tree_requires_idle;

/*
@@ -240,14 +246,15 @@ struct cfq_data {
unsigned long last_end_sync_rq;
};

-static struct cfq_rb_root *service_tree_for(enum wl_prio_t prio,
+static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
+ enum wl_prio_t prio,
enum wl_type_t type,
struct cfq_data *cfqd)
{
if (prio == IDLE_WORKLOAD)
- return &cfqd->service_tree_idle;
+ return &cfqg->service_tree_idle;

- return &cfqd->service_trees[prio][type];
+ return &cfqg->service_trees[prio][type];
}

enum cfqq_state_flags {
@@ -317,12 +324,14 @@ static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)

static inline int cfq_busy_queues_wl(enum wl_prio_t wl, struct cfq_data *cfqd)
{
+ struct cfq_group *cfqg = &cfqd->root_group;
+
if (wl == IDLE_WORKLOAD)
- return cfqd->service_tree_idle.count;
+ return cfqg->service_tree_idle.count;

- return cfqd->service_trees[wl][ASYNC_WORKLOAD].count
- + cfqd->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
- + cfqd->service_trees[wl][SYNC_WORKLOAD].count;
+ return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
+ + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
+ + cfqg->service_trees[wl][SYNC_WORKLOAD].count;
}

static void cfq_dispatch_insert(struct request_queue *, struct request *);
@@ -611,7 +620,8 @@ static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
{
struct cfq_rb_root *service_tree;

- service_tree = service_tree_for(cfqq_prio(cfqq), cfqq_type(cfqq), cfqd);
+ service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
+ cfqq_type(cfqq), cfqd);

/*
* just an approximation, should be ok.
@@ -634,7 +644,8 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct cfq_rb_root *service_tree;
int left;

- service_tree = service_tree_for(cfqq_prio(cfqq), cfqq_type(cfqq), cfqd);
+ service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
+ cfqq_type(cfqq), cfqd);
if (cfq_class_idle(cfqq)) {
rb_key = CFQ_IDLE_DELAY;
parent = rb_last(&service_tree->rb);
@@ -1070,7 +1081,8 @@ static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
{
struct cfq_rb_root *service_tree =
- service_tree_for(cfqd->serving_prio, cfqd->serving_type, cfqd);
+ service_tree_for(cfqd->serving_group, cfqd->serving_prio,
+ cfqd->serving_type, cfqd);

if (RB_EMPTY_ROOT(&service_tree->rb))
return NULL;
@@ -1222,7 +1234,8 @@ static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
* in their service tree.
*/
if (!service_tree)
- service_tree = service_tree_for(prio, cfqq_type(cfqq), cfqd);
+ service_tree = service_tree_for(cfqq->cfqg, prio,
+ cfqq_type(cfqq), cfqd);

if (service_tree->count == 0)
return true;
@@ -1381,8 +1394,9 @@ static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
}
}

-static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd, enum wl_prio_t prio,
- bool prio_changed)
+static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
+ struct cfq_group *cfqg, enum wl_prio_t prio,
+ bool prio_changed)
{
struct cfq_queue *queue;
int i;
@@ -1396,10 +1410,10 @@ static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd, enum wl_prio_t prio,
* from SYNC_NOIDLE (first choice), or just SYNC
* over ASYNC
*/
- if (service_tree_for(prio, cur_best, cfqd)->count)
+ if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
return cur_best;
cur_best = SYNC_WORKLOAD;
- if (service_tree_for(prio, cur_best, cfqd)->count)
+ if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
return cur_best;

return ASYNC_WORKLOAD;
@@ -1407,7 +1421,7 @@ static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd, enum wl_prio_t prio,

for (i = 0; i < 3; ++i) {
/* otherwise, select the one with lowest rb_key */
- queue = cfq_rb_first(service_tree_for(prio, i, cfqd));
+ queue = cfq_rb_first(service_tree_for(cfqg, prio, i, cfqd));
if (queue &&
(!key_valid || time_before(queue->rb_key, lowest_key))) {
lowest_key = queue->rb_key;
@@ -1419,12 +1433,13 @@ static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd, enum wl_prio_t prio,
return cur_best;
}

-static void choose_service_tree(struct cfq_data *cfqd)
+static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
enum wl_prio_t previous_prio = cfqd->serving_prio;
bool prio_changed;
unsigned slice;
unsigned count;
+ struct cfq_rb_root *st;

/* Choose next priority. RT > BE > IDLE */
if (cfq_busy_queues_wl(RT_WORKLOAD, cfqd))
@@ -1443,8 +1458,9 @@ static void choose_service_tree(struct cfq_data *cfqd)
* expiration time
*/
prio_changed = (cfqd->serving_prio != previous_prio);
- count = service_tree_for(cfqd->serving_prio, cfqd->serving_type, cfqd)
- ->count;
+ st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
+ cfqd);
+ count = st->count;

/*
* If priority didn't change, check workload expiration,
@@ -1456,9 +1472,10 @@ static void choose_service_tree(struct cfq_data *cfqd)

/* otherwise select new workload type */
cfqd->serving_type =
- cfq_choose_wl(cfqd, cfqd->serving_prio, prio_changed);
- count = service_tree_for(cfqd->serving_prio, cfqd->serving_type, cfqd)
- ->count;
+ cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio, prio_changed);
+ st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
+ cfqd);
+ count = st->count;

/*
* the workload slice is computed as a fraction of target latency
@@ -1482,6 +1499,12 @@ static void choose_service_tree(struct cfq_data *cfqd)
cfqd->noidle_tree_requires_idle = false;
}

+static void cfq_choose_cfqg(struct cfq_data *cfqd)
+{
+ cfqd->serving_group = &cfqd->root_group;
+ choose_service_tree(cfqd, &cfqd->root_group);
+}
+
/*
* Select a queue for service. If we have a current active queue,
* check whether to continue servicing it, or retrieve and set a new one.
@@ -1539,7 +1562,7 @@ new_queue:
* service tree
*/
if (!new_cfqq)
- choose_service_tree(cfqd);
+ cfq_choose_cfqg(cfqd);

cfqq = cfq_set_active_queue(cfqd, new_cfqq);
keep_queue:
@@ -1568,13 +1591,15 @@ static int cfq_forced_dispatch(struct cfq_data *cfqd)
struct cfq_queue *cfqq;
int dispatched = 0;
int i, j;
+ struct cfq_group *cfqg = &cfqd->root_group;
+
for (i = 0; i < 2; ++i)
for (j = 0; j < 3; ++j)
- while ((cfqq = cfq_rb_first(&cfqd->service_trees[i][j]))
+ while ((cfqq = cfq_rb_first(&cfqg->service_trees[i][j]))
!= NULL)
dispatched += __cfq_forced_dispatch_cfqq(cfqq);

- while ((cfqq = cfq_rb_first(&cfqd->service_tree_idle)) != NULL)
+ while ((cfqq = cfq_rb_first(&cfqg->service_tree_idle)) != NULL)
dispatched += __cfq_forced_dispatch_cfqq(cfqq);

cfq_slice_expired(cfqd, 0);
@@ -2045,14 +2070,26 @@ 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)
{
struct cfq_queue *cfqq, *new_cfqq = NULL;
struct cfq_io_context *cic;
+ struct cfq_group *cfqg;

retry:
+ cfqg = cfq_get_cfqg(cfqd, 1);
cic = cfq_cic_lookup(cfqd, ioc);
/* cic always exists here */
cfqq = cic_to_cfqq(cic, is_sync);
@@ -2083,6 +2120,7 @@ retry:
if (cfqq) {
cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
cfq_init_prio_data(cfqq, ioc);
+ cfq_link_cfqq_cfqg(cfqq, cfqg);
cfq_log_cfqq(cfqd, cfqq, "alloced");
} else
cfqq = &cfqd->oom_cfqq;
@@ -2935,15 +2973,19 @@ static void *cfq_init_queue(struct request_queue *q)
{
struct cfq_data *cfqd;
int i, j;
+ struct cfq_group *cfqg;

cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
if (!cfqd)
return NULL;

+ /* Init root group */
+ cfqg = &cfqd->root_group;
+
for (i = 0; i < 2; ++i)
for (j = 0; j < 3; ++j)
- cfqd->service_trees[i][j] = CFQ_RB_ROOT;
- cfqd->service_tree_idle = CFQ_RB_ROOT;
+ cfqg->service_trees[i][j] = CFQ_RB_ROOT;
+ cfqg->service_tree_idle = CFQ_RB_ROOT;

/*
* Not strictly needed (since RB_ROOT just clears the node and we
@@ -2960,6 +3002,7 @@ static void *cfq_init_queue(struct request_queue *q)
*/
cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
atomic_inc(&cfqd->oom_cfqq.ref);
+ cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);

INIT_LIST_HEAD(&cfqd->cic_list);

--
1.6.2.5


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