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Date: Mon, 21 Mar 2011 18:10:45 -0700
From: Chad Talbott <ctalbott@...gle.com>
To: jaxboe@...ionio.com, vgoyal@...hat.com
Cc: linux-kernel@...r.kernel.org, mrubin@...gle.com,
teravest@...gle.com, Chad Talbott <ctalbott@...gle.com>
Subject: [PATCH 3/3] cfq-iosched: Fair cross-group preemption (stats)
Add three counters to monitor the cross-group preemption behavior.
preempt_count:
counts the number of times this group preempted another
preempt_active:
counts the number of times this group issued an IO but
was already the active group
preempt_throttle:
number of times this group would have preempted another if it hadn't
already used up its assigned weight
Signed-off-by: Chad Talbott <ctalbott@...gle.com>
---
block/blk-cgroup.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
block/blk-cgroup.h | 18 ++++++++++++++++++
block/cfq-iosched.c | 20 +++++++++++++++++---
3 files changed, 81 insertions(+), 3 deletions(-)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index f2c553e..41ee61c 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -347,6 +347,25 @@ void blkiocg_set_start_empty_time(struct blkio_group *blkg)
}
EXPORT_SYMBOL_GPL(blkiocg_set_start_empty_time);
+void blkiocg_update_preempt_stats(struct blkio_group *blkg,
+ enum stat_type which, bool direction, bool sync)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&blkg->stats_lock, flags);
+ switch (which) {
+ case BLKIO_STAT_PREEMPT_COUNT:
+ case BLKIO_STAT_PREEMPT_ACTIVE:
+ case BLKIO_STAT_PREEMPT_THROTTLE:
+ blkio_add_stat(blkg->stats.stat_arr[which], 1, direction, sync);
+ break;
+ default:
+ BUG();
+ }
+ spin_unlock_irqrestore(&blkg->stats_lock, flags);
+}
+EXPORT_SYMBOL_GPL(blkiocg_update_preempt_stats);
+
void blkiocg_update_dequeue_stats(struct blkio_group *blkg,
unsigned long dequeue)
{
@@ -1193,6 +1212,15 @@ static int blkiocg_file_read_map(struct cgroup *cgrp, struct cftype *cft,
case BLKIO_PROP_empty_time:
return blkio_read_blkg_stats(blkcg, cft, cb,
BLKIO_STAT_EMPTY_TIME, 0);
+ case BLKIO_PROP_preempt_count:
+ return blkio_read_blkg_stats(blkcg, cft, cb,
+ BLKIO_STAT_PREEMPT_COUNT, 0);
+ case BLKIO_PROP_preempt_active:
+ return blkio_read_blkg_stats(blkcg, cft, cb,
+ BLKIO_STAT_PREEMPT_ACTIVE, 0);
+ case BLKIO_PROP_preempt_throttle:
+ return blkio_read_blkg_stats(blkcg, cft, cb,
+ BLKIO_STAT_PREEMPT_THROTTLE, 0);
#endif
default:
BUG();
@@ -1443,6 +1471,24 @@ struct cftype blkio_files[] = {
BLKIO_PROP_dequeue),
.read_map = blkiocg_file_read_map,
},
+ {
+ .name = "preempt_count",
+ .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+ BLKIO_PROP_preempt_count),
+ .read_map = blkiocg_file_read_map,
+ },
+ {
+ .name = "preempt_active",
+ .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+ BLKIO_PROP_preempt_active),
+ .read_map = blkiocg_file_read_map,
+ },
+ {
+ .name = "preempt_throttle",
+ .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+ BLKIO_PROP_preempt_throttle),
+ .read_map = blkiocg_file_read_map,
+ },
#endif
};
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 0e9cd32..d2cbdcd 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -44,6 +44,14 @@ enum stat_type {
BLKIO_STAT_WAIT_TIME,
/* Number of IOs merged */
BLKIO_STAT_MERGED,
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+ /* Number of IOs Added to active group */
+ BLKIO_STAT_PREEMPT_ACTIVE,
+ /* Number of cross-group preemptions */
+ BLKIO_STAT_PREEMPT_COUNT,
+ /* Number of cross-group preemptions disallowed by weight */
+ BLKIO_STAT_PREEMPT_THROTTLE,
+#endif
/* Number of IOs queued up */
BLKIO_STAT_QUEUED,
/* All the single valued stats go below this */
@@ -98,6 +106,9 @@ enum blkcg_file_name_prop {
BLKIO_PROP_idle_time,
BLKIO_PROP_empty_time,
BLKIO_PROP_dequeue,
+ BLKIO_PROP_preempt_count,
+ BLKIO_PROP_preempt_active,
+ BLKIO_PROP_preempt_throttle,
};
/* cgroup files owned by throttle policy */
@@ -271,6 +282,10 @@ void blkiocg_update_dequeue_stats(struct blkio_group *blkg,
void blkiocg_update_set_idle_time_stats(struct blkio_group *blkg);
void blkiocg_update_idle_time_stats(struct blkio_group *blkg);
void blkiocg_set_start_empty_time(struct blkio_group *blkg);
+void blkiocg_update_preempt_stats(struct blkio_group *blkg,
+ enum stat_type which,
+ bool direction,
+ bool sync);
#define BLKG_FLAG_FNS(name) \
static inline void blkio_mark_blkg_##name( \
@@ -301,6 +316,9 @@ static inline void blkiocg_update_set_idle_time_stats(struct blkio_group *blkg)
{}
static inline void blkiocg_update_idle_time_stats(struct blkio_group *blkg) {}
static inline void blkiocg_set_start_empty_time(struct blkio_group *blkg) {}
+static inline void blkiocg_update_preempt_stats(
+ struct blkio_group *blkg, enum stat_type which, bool direction,
+ bool sync) {}
#endif
#if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index dfcce80..0d55be3 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1171,16 +1171,30 @@ cfq_group_should_preempt(struct cfq_queue *new_cfqq, struct cfq_queue *cfqq,
u64 grace_period;
/* in-group preemption is handled elsewhere */
- if (new_cfqg == cfqg)
+ if (new_cfqg == cfqg) {
+ blkiocg_update_preempt_stats(&new_cfqg->blkg,
+ BLKIO_STAT_PREEMPT_ACTIVE,
+ rq_data_dir(rq), rq_is_sync(rq));
return false;
+ }
if (!(new_cfqg->class == BLKIO_RT_CLASS &&
cfqg->class == BLKIO_BE_CLASS))
return false;
grace_period = cfq_scale_slice(cfqq->allocated_slice, cfqg);
- return time_before64(new_cfqg->vdisktime,
- cfqg->vdisktime + grace_period);
+ if (time_before64(new_cfqg->vdisktime,
+ cfqg->vdisktime + grace_period)) {
+ blkiocg_update_preempt_stats(&new_cfqg->blkg,
+ BLKIO_STAT_PREEMPT_COUNT,
+ rq_data_dir(rq), rq_is_sync(rq));
+ return true;
+ }
+
+ blkiocg_update_preempt_stats(&new_cfqg->blkg,
+ BLKIO_STAT_PREEMPT_THROTTLE,
+ rq_data_dir(rq), rq_is_sync(rq));
+ return false;
}
#else /* GROUP_IOSCHED */
--
1.7.3.1
--
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