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blkio: Introduce the notion of cfq groups
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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>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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Vivek Goyal authored and Jens Axboe committed Dec 3, 2009
1 parent bf79193 commit cdb16e8
Showing 1 changed file with 75 additions and 33 deletions.
108 changes: 75 additions & 33 deletions block/cfq-iosched.c
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Original file line number Diff line number Diff line change
Expand Up @@ -132,6 +132,7 @@ struct cfq_queue {

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

/*
Expand All @@ -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;

/*
Expand Down Expand Up @@ -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 {
Expand Down Expand Up @@ -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 *);
Expand Down Expand Up @@ -612,7 +621,7 @@ static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
/*
* just an approximation, should be ok.
*/
return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
}

Expand All @@ -630,7 +639,8 @@ 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);
Expand Down Expand Up @@ -1066,7 +1076,8 @@ 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;
Expand Down Expand Up @@ -1218,7 +1229,8 @@ 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;
Expand Down Expand Up @@ -1377,8 +1389,9 @@ 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;
Expand All @@ -1392,18 +1405,18 @@ 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;
}

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;
Expand All @@ -1415,12 +1428,13 @@ 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))
Expand All @@ -1439,8 +1453,9 @@ 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,
Expand All @@ -1452,9 +1467,10 @@ 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
Expand All @@ -1478,6 +1494,12 @@ 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.
Expand Down Expand Up @@ -1535,7 +1557,7 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
* service tree
*/
if (!new_cfqq)
choose_service_tree(cfqd);
cfq_choose_cfqg(cfqd);

cfqq = cfq_set_active_queue(cfqd, new_cfqq);
keep_queue:
Expand Down Expand Up @@ -1564,13 +1586,15 @@ 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);
Expand Down Expand Up @@ -2041,14 +2065,26 @@ 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);
Expand Down Expand Up @@ -2079,6 +2115,7 @@ cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
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;
Expand Down Expand Up @@ -2931,15 +2968,19 @@ 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
Expand All @@ -2956,6 +2997,7 @@ 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);

Expand Down

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