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Message-Id: <11774025432951-git-send-email-jens.axboe@oracle.com>
Date: Tue, 24 Apr 2007 10:15:36 +0200
From: Jens Axboe <jens.axboe@...cle.com>
To: linux-kernel@...r.kernel.org
Cc: Jens Axboe <jens.axboe@...cle.com>
Subject: [PATCH 8/15] cfq-iosched: style cleanups and comments
Signed-off-by: Jens Axboe <jens.axboe@...cle.com>
---
block/cfq-iosched.c | 66 ++++++++++++++++++++++++++++++++++++++------------
1 files changed, 50 insertions(+), 16 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index e6cc77f..f86ff4d 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -222,7 +222,7 @@ CFQ_CFQQ_FNS(slice_new);
static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short);
static void cfq_dispatch_insert(request_queue_t *, struct request *);
-static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
+static struct cfq_queue *cfq_get_queue(struct cfq_data *, unsigned int, struct task_struct *, gfp_t);
/*
* scheduler run of queue, if there are requests pending and no one in the
@@ -389,6 +389,9 @@ cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
}
}
+/*
+ * The below is leftmost cache rbtree addon
+ */
static struct rb_node *cfq_rb_first(struct cfq_rb_root *root)
{
if (root->left)
@@ -442,13 +445,18 @@ static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
return ((cfqd->busy_queues - 1) * cfq_prio_slice(cfqd, 1, 0));
}
+/*
+ * The cfqd->service_tree 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.
+ */
static void cfq_service_tree_add(struct cfq_data *cfqd,
struct cfq_queue *cfqq)
{
struct rb_node **p = &cfqd->service_tree.rb.rb_node;
struct rb_node *parent = NULL;
unsigned long rb_key;
- int left = 1;
+ int left;
rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
rb_key += cfqq->slice_resid;
@@ -464,6 +472,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd,
cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
}
+ left = 1;
while (*p) {
struct cfq_queue *__cfqq;
struct rb_node **n;
@@ -503,17 +512,16 @@ static void cfq_service_tree_add(struct cfq_data *cfqd,
rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb);
}
+/*
+ * Update cfqq's position in the service tree.
+ */
static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
{
- struct cfq_data *cfqd = cfqq->cfqd;
-
/*
* Resorting requires the cfqq to be on the RR list already.
*/
- if (!cfq_cfqq_on_rr(cfqq))
- return;
-
- cfq_service_tree_add(cfqd, cfqq);
+ if (cfq_cfqq_on_rr(cfqq))
+ cfq_service_tree_add(cfqq->cfqd, cfqq);
}
/*
@@ -530,6 +538,10 @@ cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
cfq_resort_rr_list(cfqq, 0);
}
+/*
+ * Called when the cfqq no longer has requests pending, remove it from
+ * the service tree.
+ */
static inline void
cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
@@ -648,8 +660,7 @@ static void cfq_remove_request(struct request *rq)
}
}
-static int
-cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
+static int cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct request *__rq;
@@ -775,6 +786,10 @@ static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted,
__cfq_slice_expired(cfqd, cfqq, preempted, timed_out);
}
+/*
+ * Get next queue for service. Unless we have a queue preemption,
+ * we'll simply select the first cfqq in the service tree.
+ */
static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq = NULL;
@@ -786,10 +801,11 @@ static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
cfqq = list_entry_cfqq(cfqd->cur_rr.next);
} else if (!RB_EMPTY_ROOT(&cfqd->service_tree.rb)) {
struct rb_node *n = cfq_rb_first(&cfqd->service_tree);
- unsigned long end;
cfqq = rb_entry(n, struct cfq_queue, rb_node);
if (cfq_class_idle(cfqq)) {
+ unsigned long end;
+
/*
* if we have idle queues and no rt or be queues had
* pending requests, either allow immediate service if
@@ -807,6 +823,9 @@ static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
return cfqq;
}
+/*
+ * Get and set a new active queue for service.
+ */
static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq;
@@ -892,6 +911,9 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
}
+/*
+ * Move request from internal lists to the request queue dispatch list.
+ */
static void cfq_dispatch_insert(request_queue_t *q, struct request *rq)
{
struct cfq_queue *cfqq = RQ_CFQQ(rq);
@@ -938,7 +960,8 @@ cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
}
/*
- * get next queue for service
+ * 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.
*/
static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
{
@@ -979,6 +1002,10 @@ keep_queue:
return cfqq;
}
+/*
+ * Dispatch some requests from cfqq, moving them to the request queue
+ * dispatch list.
+ */
static int
__cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
int max_dispatch)
@@ -1053,6 +1080,10 @@ static int cfq_forced_dispatch_cfqqs(struct list_head *list)
return dispatched;
}
+/*
+ * Drain our current requests. Used for barriers and when switching
+ * io schedulers on-the-fly.
+ */
static int cfq_forced_dispatch(struct cfq_data *cfqd)
{
int dispatched = 0;
@@ -1218,10 +1249,6 @@ static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
}
}
-
-/*
- * Called with interrupts disabled
- */
static void cfq_exit_single_io_context(struct cfq_io_context *cic)
{
struct cfq_data *cfqd = cic->key;
@@ -1235,6 +1262,10 @@ static void cfq_exit_single_io_context(struct cfq_io_context *cic)
}
}
+/*
+ * The process that ioc belongs to has exited, we need to clean up
+ * and put the internal structures we have that belongs to that process.
+ */
static void cfq_exit_io_context(struct io_context *ioc)
{
struct cfq_io_context *__cic;
@@ -1421,6 +1452,9 @@ out:
return cfqq;
}
+/*
+ * We drop cfq io contexts lazily, so we may find a dead one.
+ */
static void
cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
{
--
1.5.1.1.190.g74474
-
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