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Subject[RFC][PATCH 5/9] cgroups: block: cfq: I/O bandwidth controlling subsystem for CGroups based on CFQ
From
Date
From: Vasily Tarasov <vtaras@openvz.org>

Switches the CFQ scheduler to use per-cgroup queue tree,
instead one queue tree per device.

Signed-off-by: Vasily Tarasov <vtaras@openvz.org>

---

--- linux-2.6.25-rc5-mm1/include/linux/cfq-iosched.h.switch 2008-02-15 01:07:29.000000000 -0500
+++ linux-2.6.25-rc5-mm1/include/linux/cfq-iosched.h 2008-02-15 01:09:09.000000000 -0500
@@ -70,9 +70,8 @@ struct cfq_data {
struct cfqio_cgroup_data cfqio_cgroup;
#endif
/*
- * rr list of queues with requests and the count of them
+ * count of queues
*/
- struct cfq_rb_root service_tree;
unsigned int busy_queues;

int rq_in_driver;
--- linux-2.6.25-rc5-mm1/block/cfq-iosched.c.switch 2008-02-15 01:08:25.000000000 -0500
+++ linux-2.6.25-rc5-mm1/block/cfq-iosched.c 2008-02-15 01:09:09.000000000 -0500
@@ -354,6 +354,7 @@ static unsigned long cfq_slice_offset(st
static void cfq_service_tree_add(struct cfq_data *cfqd,
struct cfq_queue *cfqq, int add_front)
{
+ struct cfqio_cgroup_data *cfqio_cgrp = cfqq->cfqio_cgrp;
struct rb_node **p, *parent;
struct cfq_queue *__cfqq;
unsigned long rb_key;
@@ -361,7 +362,7 @@ static void cfq_service_tree_add(struct

if (cfq_class_idle(cfqq)) {
rb_key = CFQ_IDLE_DELAY;
- parent = rb_last(&cfqd->service_tree.rb);
+ parent = rb_last(&cfqio_cgrp->service_tree.rb);
if (parent && parent != &cfqq->rb_node) {
__cfqq = rb_entry(parent, struct cfq_queue, rb_node);
rb_key += __cfqq->rb_key;
@@ -381,12 +382,12 @@ static void cfq_service_tree_add(struct
if (rb_key == cfqq->rb_key)
return;

- cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
+ cfq_rb_erase(&cfqq->rb_node, &cfqio_cgrp->service_tree);
}

left = 1;
parent = NULL;
- p = &cfqd->service_tree.rb.rb_node;
+ p = &cfqio_cgrp->service_tree.rb.rb_node;
while (*p) {
struct rb_node **n;

@@ -418,11 +419,11 @@ static void cfq_service_tree_add(struct
}

if (left)
- cfqd->service_tree.left = &cfqq->rb_node;
+ cfqio_cgrp->service_tree.left = &cfqq->rb_node;

cfqq->rb_key = rb_key;
rb_link_node(&cfqq->rb_node, parent, p);
- rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb);
+ rb_insert_color(&cfqq->rb_node, &cfqio_cgrp->service_tree.rb);
}

/*
@@ -456,11 +457,12 @@ static void cfq_add_cfqq_rr(struct cfq_d
*/
static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
+ struct cfqio_cgroup_data *cfqio_cgrp = cfqq->cfqio_cgrp;
BUG_ON(!cfq_cfqq_on_rr(cfqq));
cfq_clear_cfqq_on_rr(cfqq);

if (!RB_EMPTY_NODE(&cfqq->rb_node))
- cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
+ cfq_rb_erase(&cfqq->rb_node, &cfqio_cgrp->service_tree);

BUG_ON(!cfqd->busy_queues);
cfqd->busy_queues--;
@@ -704,10 +706,16 @@ static inline void cfq_slice_expired(str
*/
static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
{
- if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
+ struct cfqio_cgroup_data *cfqio_cgrp;
+
+ cfqio_cgrp = cfqd->active_cfqio_cgroup;
+ if (!cfqio_cgrp)
+ return NULL;
+
+ if (RB_EMPTY_ROOT(&cfqio_cgrp->service_tree.rb))
return NULL;

- return cfq_rb_first(&cfqd->service_tree);
+ return cfq_rb_first(&cfqio_cgrp->service_tree);
}

/*
@@ -964,7 +972,7 @@ static int __cfq_forced_dispatch_cfqq(st
* Drain our current requests. Used for barriers and when switching
* io schedulers on-the-fly.
*/
-static int cfq_forced_dispatch(struct cfq_data *cfqd)
+static int __cfq_forced_dispatch(struct cfqio_cgroup_data *cfqd)
{
struct cfq_queue *cfqq;
int dispatched = 0;
@@ -972,6 +980,25 @@ static int cfq_forced_dispatch(struct cf
while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL)
dispatched += __cfq_forced_dispatch_cfqq(cfqq);

+ return dispatched;
+}
+
+static int cfq_forced_dispatch(struct cfq_data *cfqd)
+{
+ struct cfqio_cgroup_data *cfqio_cgrp;
+ struct cfqio_cgroup_data *cfqio_cgrp_tmp;
+ int dispatched;
+
+ dispatched = 0;
+
+ /*
+ * We use _safe iterating here because __cfq_forced_dispatch()
+ * produces list_del() implicitly
+ */
+ list_for_each_entry_safe(cfqio_cgrp, cfqio_cgrp_tmp,
+ &cfqd->act_cfqio_cgrp_head, act_cfqio_cgrp_list)
+ dispatched += __cfq_forced_dispatch(cfqio_cgrp);
+
cfq_slice_expired(cfqd, 0);

BUG_ON(cfqd->busy_queues);
@@ -2025,7 +2052,6 @@ static void *cfq_init_queue(struct reque
if (!cfqd)
return NULL;

- cfqd->service_tree = CFQ_RB_ROOT;
#ifndef CONFIG_CGROUP_CFQIO
cfqio_init_cfqio_cgroup(&cfqd->cfqio_cgroup);
#endif

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