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Subject[PATCH 5/6] io_context sharing - anticipatory changes
Date
changes to anticipatory io scheduler for io_context sharing

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
block/as-iosched.c | 34 ++++++++++++++++++++++++++++------
1 files changed, 28 insertions(+), 6 deletions(-)
diff --git a/block/as-iosched.c b/block/as-iosched.c
index cb5e53b..b201d16 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -170,9 +170,11 @@ static void free_as_io_context(struct as_io_context *aic)

static void as_trim(struct io_context *ioc)
{
+ spin_lock(&ioc->lock);
if (ioc->aic)
free_as_io_context(ioc->aic);
ioc->aic = NULL;
+ spin_unlock(&ioc->lock);
}

/* Called when the task exits */
@@ -462,7 +464,9 @@ static void as_antic_timeout(unsigned long data)
spin_lock_irqsave(q->queue_lock, flags);
if (ad->antic_status == ANTIC_WAIT_REQ
|| ad->antic_status == ANTIC_WAIT_NEXT) {
- struct as_io_context *aic = ad->io_context->aic;
+ struct as_io_context *aic;
+ spin_lock(&ad->io_context->lock);
+ aic = ad->io_context->aic;

ad->antic_status = ANTIC_FINISHED;
kblockd_schedule_work(&ad->antic_work);
@@ -475,6 +479,7 @@ static void as_antic_timeout(unsigned long data)
/* process not "saved" by a cooperating request */
ad->exit_no_coop = (7*ad->exit_no_coop + 256)/8;
}
+ spin_unlock(&ad->io_context->lock);
}
spin_unlock_irqrestore(q->queue_lock, flags);
}
@@ -635,9 +640,11 @@ static int as_can_break_anticipation(struct as_data *ad, struct request *rq)

ioc = ad->io_context;
BUG_ON(!ioc);
+ spin_lock(&ioc->lock);

if (rq && ioc == RQ_IOC(rq)) {
/* request from same process */
+ spin_unlock(&ioc->lock);
return 1;
}

@@ -646,20 +653,25 @@ static int as_can_break_anticipation(struct as_data *ad, struct request *rq)
* In this situation status should really be FINISHED,
* however the timer hasn't had the chance to run yet.
*/
+ spin_unlock(&ioc->lock);
return 1;
}

aic = ioc->aic;
- if (!aic)
+ if (!aic) {
+ spin_unlock(&ioc->lock);
return 0;
+ }

if (atomic_read(&aic->nr_queued) > 0) {
/* process has more requests queued */
+ spin_unlock(&ioc->lock);
return 1;
}

if (atomic_read(&aic->nr_dispatched) > 0) {
/* process has more requests dispatched */
+ spin_unlock(&ioc->lock);
return 1;
}

@@ -680,6 +692,7 @@ static int as_can_break_anticipation(struct as_data *ad, struct request *rq)
}

as_update_iohist(ad, aic, rq);
+ spin_unlock(&ioc->lock);
return 1;
}

@@ -688,20 +701,27 @@ static int as_can_break_anticipation(struct as_data *ad, struct request *rq)
if (aic->ttime_samples == 0)
ad->exit_prob = (7*ad->exit_prob + 256)/8;

- if (ad->exit_no_coop > 128)
+ if (ad->exit_no_coop > 128) {
+ spin_unlock(&ioc->lock);
return 1;
+ }
}

if (aic->ttime_samples == 0) {
- if (ad->new_ttime_mean > ad->antic_expire)
+ if (ad->new_ttime_mean > ad->antic_expire) {
+ spin_unlock(&ioc->lock);
return 1;
- if (ad->exit_prob * ad->exit_no_coop > 128*256)
+ }
+ if (ad->exit_prob * ad->exit_no_coop > 128*256) {
+ spin_unlock(&ioc->lock);
return 1;
+ }
} else if (aic->ttime_mean > ad->antic_expire) {
/* the process thinks too much between requests */
+ spin_unlock(&ioc->lock);
return 1;
}
-
+ spin_unlock(&ioc->lock);
return 0;
}

@@ -1255,7 +1275,9 @@ static void as_merged_requests(struct request_queue *q, struct request *req,
* Don't copy here but swap, because when anext is
* removed below, it must contain the unused context
*/
+ double_spin_lock(&rioc->lock, &nioc->lock, rioc < nioc);
swap_io_context(&rioc, &nioc);
+ double_spin_unlock(&rioc->lock, &nioc->lock, rioc < nioc);
}
}

--
1.5.4.rc2.84.gf85fd


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