lkml.org 
[lkml]   [2009]   [Oct]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 3/5] cfq-iosched: reimplement priorities using different service trees
Date
We use different service trees for different priority classes.
This allows a simplification in the service tree insertion code, that no
longer has to consider priority while walking the tree.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
---
block/cfq-iosched.c | 114 +++++++++++++++++++++++++++++++++++---------------
1 files changed, 80 insertions(+), 34 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index b707573..4da42cd 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -134,15 +134,31 @@ struct cfq_queue {
};

/*
+ * Index in the service_trees.
+ * IDLE is handled separately, so it has negative index
+ */
+enum wl_prio_t {
+ IDLE_WORKLOAD = -1,
+ BE_WORKLOAD = 0,
+ RT_WORKLOAD = 1
+};
+
+/*
* Per block device queue structure
*/
struct cfq_data {
struct request_queue *queue;

/*
- * rr list of queues with requests and the count of them
+ * 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];
+ struct cfq_rb_root service_tree_idle;
+ /*
+ * The priority currently being served
*/
- struct cfq_rb_root service_tree;
+ enum wl_prio_t serving_prio;

/*
* Each priority tree is sorted by next_request position. These
@@ -152,7 +168,6 @@ struct cfq_data {
struct rb_root prio_trees[CFQ_PRIO_LISTS];

unsigned int busy_queues;
- unsigned int busy_rt_queues;
unsigned int busy_queues_avg[2];

int rq_in_driver[2];
@@ -205,6 +220,15 @@ struct cfq_data {
unsigned long last_end_sync_rq;
};

+static struct cfq_rb_root *service_tree_for(enum wl_prio_t prio,
+ struct cfq_data *cfqd)
+{
+ if (prio == IDLE_WORKLOAD)
+ return &cfqd->service_tree_idle;
+
+ return &cfqd->service_trees[prio];
+}
+
enum cfqq_state_flags {
CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
@@ -249,6 +273,23 @@ CFQ_CFQQ_FNS(coop);
#define cfq_log(cfqd, fmt, args...) \
blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)

+static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
+{
+ if (cfq_class_idle(cfqq))
+ return IDLE_WORKLOAD;
+ if (cfq_class_rt(cfqq))
+ return RT_WORKLOAD;
+ return BE_WORKLOAD;
+}
+
+static inline int cfq_busy_queues_wl(enum wl_prio_t wl, struct cfq_data *cfqd)
+{
+ if (wl == IDLE_WORKLOAD)
+ return cfqd->service_tree_idle.count;
+
+ return cfqd->service_trees[wl].count;
+}
+
static void cfq_dispatch_insert(struct request_queue *, struct request *);
static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
struct io_context *, gfp_t);
@@ -332,10 +373,7 @@ cfq_get_avg_queues(struct cfq_data *cfqd, bool rt) {
unsigned min_q, max_q;
unsigned mult = cfq_hist_divisor - 1;
unsigned round = cfq_hist_divisor / 2;
- unsigned busy = cfqd->busy_rt_queues;
-
- if (!rt)
- busy = cfqd->busy_queues - cfqd->busy_rt_queues;
+ unsigned busy = cfq_busy_queues_wl(rt, cfqd);

min_q = min(cfqd->busy_queues_avg[rt], busy);
max_q = max(cfqd->busy_queues_avg[rt], busy);
@@ -546,7 +584,7 @@ static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
}

/*
- * The cfqd->service_tree holds all pending cfq_queue's that have
+ * The cfqd->service_trees holds all pending cfq_queue's that have
* requests waiting to be processed. It is sorted in the order that
* we will service the queues.
*/
@@ -556,9 +594,10 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct rb_node **p, *parent;
struct cfq_queue *__cfqq;
unsigned long rb_key;
- struct cfq_rb_root *service_tree = &cfqd->service_tree;
+ struct cfq_rb_root *service_tree;
int left;

+ service_tree = service_tree_for(cfqq_prio(cfqq), cfqd);
if (cfq_class_idle(cfqq)) {
rb_key = CFQ_IDLE_DELAY;
parent = rb_last(&service_tree->rb);
@@ -587,7 +626,8 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
/*
* same position, nothing more to do
*/
- if (rb_key == cfqq->rb_key)
+ if (rb_key == cfqq->rb_key &&
+ cfqq->service_tree == service_tree)
return;

cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
@@ -605,25 +645,14 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
__cfqq = rb_entry(parent, struct cfq_queue, rb_node);

/*
- * sort RT queues first, we always want to give
- * preference to them. IDLE queues goes to the back.
- * after that, sort on the next service time.
+ * sort by key, that represents service time.
*/
- if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
- n = &(*p)->rb_left;
- else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
- n = &(*p)->rb_right;
- else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq))
- n = &(*p)->rb_left;
- else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
- n = &(*p)->rb_right;
- else if (time_before(rb_key, __cfqq->rb_key))
+ if (time_before(rb_key, __cfqq->rb_key))
n = &(*p)->rb_left;
- else
+ else {
n = &(*p)->rb_right;
-
- if (n == &(*p)->rb_right)
left = 0;
+ }

p = n;
}
@@ -722,8 +751,7 @@ static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
BUG_ON(cfq_cfqq_on_rr(cfqq));
cfq_mark_cfqq_on_rr(cfqq);
cfqd->busy_queues++;
- if (cfq_class_rt(cfqq))
- cfqd->busy_rt_queues++;
+
cfq_resort_rr_list(cfqd, cfqq);
}

@@ -748,8 +776,6 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)

BUG_ON(!cfqd->busy_queues);
cfqd->busy_queues--;
- if (cfq_class_rt(cfqq))
- cfqd->busy_rt_queues--;
}

/*
@@ -1003,10 +1029,12 @@ 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)
{
- if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
- return NULL;
+ struct cfq_rb_root *service_tree =
+ service_tree_for(cfqd->serving_prio, cfqd);

- return cfq_rb_first(&cfqd->service_tree);
+ if (RB_EMPTY_ROOT(&service_tree->rb))
+ return NULL;
+ return cfq_rb_first(service_tree);
}

/*
@@ -1123,6 +1151,10 @@ static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
if (CFQQ_SEEKY(cfqq))
return NULL;

+ /* we don't want to mix processes with different characteristics */
+ if (cfqq->service_tree != cur_cfqq->service_tree)
+ return NULL;
+
return cfqq;
}

@@ -1336,6 +1368,14 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
expire:
cfq_slice_expired(cfqd, 0);
new_queue:
+ if (!new_cfqq) {
+ if (cfq_busy_queues_wl(RT_WORKLOAD, cfqd))
+ cfqd->serving_prio = RT_WORKLOAD;
+ else if (cfq_busy_queues_wl(BE_WORKLOAD, cfqd))
+ cfqd->serving_prio = BE_WORKLOAD;
+ else
+ cfqd->serving_prio = IDLE_WORKLOAD;
+ }
cfqq = cfq_set_active_queue(cfqd, new_cfqq);
keep_queue:
return cfqq;
@@ -1362,8 +1402,12 @@ static int cfq_forced_dispatch(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq;
int dispatched = 0;
+ int i;
+ for (i = 0; i < 2; ++i)
+ while ((cfqq = cfq_rb_first(&cfqd->service_trees[i])) != NULL)
+ dispatched += __cfq_forced_dispatch_cfqq(cfqq);

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

cfq_slice_expired(cfqd, 0);
@@ -2698,7 +2742,9 @@ static void *cfq_init_queue(struct request_queue *q)
if (!cfqd)
return NULL;

- cfqd->service_tree = CFQ_RB_ROOT;
+ for (i = 0; i < 2; ++i)
+ cfqd->service_trees[i] = CFQ_RB_ROOT;
+ cfqd->service_tree_idle = CFQ_RB_ROOT;

/*
* Not strictly needed (since RB_ROOT just clears the node and we
--
1.6.2.5



\
 
 \ /
  Last update: 2009-10-26 22:47    [from the cache]
©2003-2011 Jasper Spaans