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From: Divyesh Shah on 24 Mar 2010 20:30
These extra logging messages have helped us debug some issues we've noticed in
earlier IO controller versions and should be useful now as well. The extra
logging covers:
- idling behavior. Since there are so many conditions based on which we decide
to idle or not, this patch adds a log message for some conditions that we've
found useful.
- workload slices and current prio and workload type

Signed-off-by: Divyesh Shah<dpshah(a)google.com>
---

block/cfq-iosched.c | 17 +++++++++++++++--
1 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index e6910dc..556124a 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1646,6 +1646,10 @@ static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
if (!cfqq)
cfqq = cfq_get_next_queue(cfqd);

+ if (cfqq)
+ cfq_log_cfqq(cfqd, cfqq, "New timeslice for wl_prio:%d "
+ "wl_type:%d", cfqd->serving_prio,
+ cfqd->serving_type);
__cfq_set_active_queue(cfqd, cfqq);
return cfqq;
}
@@ -1789,7 +1793,11 @@ static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
* Otherwise, we do only if they are the last ones
* in their service tree.
*/
- return service_tree->count == 1 && cfq_cfqq_sync(cfqq);
+ if (service_tree->count == 1 && cfq_cfqq_sync(cfqq))
+ return 1;
+ cfq_log_cfqq(cfqd, cfqq, "Not idling. queue_count:%d",
+ service_tree->count);
+ return 0;
}

static void cfq_arm_slice_timer(struct cfq_data *cfqd)
@@ -1834,8 +1842,11 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
* time slice.
*/
if (sample_valid(cic->ttime_samples) &&
- (cfqq->slice_end - jiffies < cic->ttime_mean))
+ (cfqq->slice_end - jiffies < cic->ttime_mean)) {
+ cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%d",
+ cic->ttime_mean);
return;
+ }

cfq_mark_cfqq_wait_request(cfqq);

@@ -2043,6 +2054,7 @@ static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
slice = max(slice, 2 * cfqd->cfq_slice_idle);

slice = max_t(unsigned, slice, CFQ_MIN_TT);
+ cfq_log(cfqd, "workload slice:%d", slice);
cfqd->workload_expires = jiffies + slice;
cfqd->noidle_tree_requires_idle = false;
}
@@ -3309,6 +3321,7 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
if (cfq_should_wait_busy(cfqd, cfqq)) {
cfqq->slice_end = jiffies + cfqd->cfq_slice_idle;
cfq_mark_cfqq_wait_busy(cfqq);
+ cfq_log_cfqq(cfqd, cfqq, "will busy wait");
}

/*

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Prev: [PATCH] Expose the statistics in blkio.time and blkio.sectors for the root cgroup
Next: Prevent nested interrupts when the IRQ stack is near overflowing v2