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Date: Mon, 19 Mar 2012 15:10:58 -0700
From: Tejun Heo <tj@...nel.org>
To: axboe@...nel.dk, vgoyal@...hat.com
Cc: linux-kernel@...r.kernel.org, ctalbott@...gle.com, rni@...gle.com,
Tejun Heo <tj@...nel.org>
Subject: [PATCH 3/4] cfq: don't use icq_get_changed()
cfq caches the associated cfqq's for a given cic. The cache needs to
be flushed if the cic's ioprio or blkcg has changed. It is currently
done by requiring the changing action to set the respective
ICQ_*_CHANGED bit in the icq and testing it from cfq_set_request(),
which involves iterating through all the affected icqs.
All cfq wants to know is whether ioprio and/or blkcg have changed
since the last flush and can be easily achieved by just remembering
the current ioprio and blkcg ID in cic.
This patch adds cic->{ioprio|blkcg_id}, updates all ioprio users to
use the remembered value instead, and updates cfq_set_request() path
such that, instead of using icq_get_changed(), the current values are
compared against the remembered ones and trigger appropriate flush
action if not. Condition tests are moved inside both _changed
functions which are now named check_ioprio_changed() and
check_blkcg_changed().
ioprio.h::task_ioprio*() can't be used anymore and replaced with
open-coded IOPRIO_CLASS_NONE case in cfq_async_queue_prio().
Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Vivek Goyal <vgoyal@...hat.com>
---
block/cfq-iosched.c | 63 ++++++++++++++++++++++++++++++-----------------
include/linux/ioprio.h | 22 ++++-------------
2 files changed, 45 insertions(+), 40 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 9e8624e..7c3893d 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -218,6 +218,10 @@ struct cfq_io_cq {
struct io_cq icq; /* must be the first member */
struct cfq_queue *cfqq[2];
struct cfq_ttime ttime;
+ int ioprio; /* the current ioprio */
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+ uint64_t blkcg_id; /* the current blkcg ID */
+#endif
};
/*
@@ -2568,7 +2572,7 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq, struct cfq_io_cq *cic)
if (!cfq_cfqq_prio_changed(cfqq))
return;
- ioprio_class = IOPRIO_PRIO_CLASS(cic->icq.ioc->ioprio);
+ ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
switch (ioprio_class) {
default:
printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
@@ -2580,11 +2584,11 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq, struct cfq_io_cq *cic)
cfqq->ioprio_class = task_nice_ioclass(tsk);
break;
case IOPRIO_CLASS_RT:
- cfqq->ioprio = task_ioprio(cic->icq.ioc);
+ cfqq->ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
cfqq->ioprio_class = IOPRIO_CLASS_RT;
break;
case IOPRIO_CLASS_BE:
- cfqq->ioprio = task_ioprio(cic->icq.ioc);
+ cfqq->ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
cfqq->ioprio_class = IOPRIO_CLASS_BE;
break;
case IOPRIO_CLASS_IDLE:
@@ -2602,12 +2606,17 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq, struct cfq_io_cq *cic)
cfq_clear_cfqq_prio_changed(cfqq);
}
-static void changed_ioprio(struct cfq_io_cq *cic, struct bio *bio)
+static void check_ioprio_changed(struct cfq_io_cq *cic, struct bio *bio)
{
+ int ioprio = cic->icq.ioc->ioprio;
struct cfq_data *cfqd = cic_to_cfqd(cic);
struct cfq_queue *cfqq;
- if (unlikely(!cfqd))
+ /*
+ * Check whether ioprio has changed. The condition may trigger
+ * spuriously on a newly created cic but there's no harm.
+ */
+ if (unlikely(!cfqd) || likely(cic->ioprio == ioprio))
return;
cfqq = cic->cfqq[BLK_RW_ASYNC];
@@ -2624,6 +2633,8 @@ static void changed_ioprio(struct cfq_io_cq *cic, struct bio *bio)
cfqq = cic->cfqq[BLK_RW_SYNC];
if (cfqq)
cfq_mark_cfqq_prio_changed(cfqq);
+
+ cic->ioprio = ioprio;
}
static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
@@ -2647,17 +2658,24 @@ static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
}
#ifdef CONFIG_CFQ_GROUP_IOSCHED
-static void changed_cgroup(struct cfq_io_cq *cic)
+static void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
{
- struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
struct cfq_data *cfqd = cic_to_cfqd(cic);
- struct request_queue *q;
+ struct cfq_queue *sync_cfqq;
+ uint64_t id;
- if (unlikely(!cfqd))
- return;
+ rcu_read_lock();
+ id = bio_blkio_cgroup(bio)->id;
+ rcu_read_unlock();
- q = cfqd->queue;
+ /*
+ * Check whether blkcg has changed. The condition may trigger
+ * spuriously on a newly created cic but there's no harm.
+ */
+ if (unlikely(!cfqd) || likely(cic->blkcg_id == id))
+ return;
+ sync_cfqq = cic_to_cfqq(cic, 1);
if (sync_cfqq) {
/*
* Drop reference to sync queue. A new sync queue will be
@@ -2667,7 +2685,11 @@ static void changed_cgroup(struct cfq_io_cq *cic)
cic_set_cfqq(cic, NULL, 1);
cfq_put_queue(sync_cfqq);
}
+
+ cic->blkcg_id = id;
}
+#else
+static inline void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio) { }
#endif /* CONFIG_CFQ_GROUP_IOSCHED */
static struct cfq_queue *
@@ -2731,6 +2753,9 @@ cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
switch (ioprio_class) {
case IOPRIO_CLASS_RT:
return &cfqd->async_cfqq[0][ioprio];
+ case IOPRIO_CLASS_NONE:
+ ioprio = IOPRIO_NORM;
+ /* fall through */
case IOPRIO_CLASS_BE:
return &cfqd->async_cfqq[1][ioprio];
case IOPRIO_CLASS_IDLE:
@@ -2744,8 +2769,8 @@ static struct cfq_queue *
cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
struct bio *bio, gfp_t gfp_mask)
{
- const int ioprio = task_ioprio(cic->icq.ioc);
- const int ioprio_class = task_ioprio_class(cic->icq.ioc);
+ const int ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
+ const int ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
struct cfq_queue **async_cfqq = NULL;
struct cfq_queue *cfqq = NULL;
@@ -3303,21 +3328,13 @@ cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
const int rw = rq_data_dir(rq);
const bool is_sync = rq_is_sync(rq);
struct cfq_queue *cfqq;
- unsigned int changed;
might_sleep_if(gfp_mask & __GFP_WAIT);
spin_lock_irq(q->queue_lock);
- /* handle changed notifications */
- changed = icq_get_changed(&cic->icq);
- if (unlikely(changed & ICQ_IOPRIO_CHANGED))
- changed_ioprio(cic, bio);
-#ifdef CONFIG_CFQ_GROUP_IOSCHED
- if (unlikely(changed & ICQ_CGROUP_CHANGED))
- changed_cgroup(cic);
-#endif
-
+ check_ioprio_changed(cic, bio);
+ check_blkcg_changed(cic, bio);
new_queue:
cfqq = cic_to_cfqq(cic, is_sync);
if (!cfqq || cfqq == &cfqd->oom_cfqq) {
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index 76dad48..beb9ce1 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -42,26 +42,14 @@ enum {
};
/*
- * if process has set io priority explicitly, use that. if not, convert
- * the cpu scheduler nice value to an io priority
+ * Fallback BE priority
*/
#define IOPRIO_NORM (4)
-static inline int task_ioprio(struct io_context *ioc)
-{
- if (ioprio_valid(ioc->ioprio))
- return IOPRIO_PRIO_DATA(ioc->ioprio);
-
- return IOPRIO_NORM;
-}
-
-static inline int task_ioprio_class(struct io_context *ioc)
-{
- if (ioprio_valid(ioc->ioprio))
- return IOPRIO_PRIO_CLASS(ioc->ioprio);
-
- return IOPRIO_CLASS_BE;
-}
+/*
+ * if process has set io priority explicitly, use that. if not, convert
+ * the cpu scheduler nice value to an io priority
+ */
static inline int task_nice_ioprio(struct task_struct *task)
{
return (task_nice(task) + 20) / 5;
--
1.7.7.3
--
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