[PATCH 06/10] block: kill request allocation batching
From: Jens Axboe
Date: Fri Jan 21 2011 - 20:18:11 EST
Signed-off-by: Jens Axboe <jaxboe@xxxxxxxxxxxx>
---
block/blk-core.c | 81 ++---------------------------------------------
block/blk-settings.c | 1 -
block/blk.h | 6 ---
include/linux/blkdev.h | 1 -
4 files changed, 4 insertions(+), 85 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 7ab6620..54b5987 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -593,40 +593,6 @@ blk_alloc_request(struct request_queue *q, int flags, int priv, gfp_t gfp_mask)
return rq;
}
-/*
- * ioc_batching returns true if the ioc is a valid batching request and
- * should be given priority access to a request.
- */
-static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
-{
- if (!ioc)
- return 0;
-
- /*
- * Make sure the process is able to allocate at least 1 request
- * even if the batch times out, otherwise we could theoretically
- * lose wakeups.
- */
- return ioc->nr_batch_requests == q->nr_batching ||
- (ioc->nr_batch_requests > 0
- && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
-}
-
-/*
- * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
- * will cause the process to be a "batcher" on all queues in the system. This
- * is the behaviour we want though - once it gets a wakeup it should be given
- * a nice run.
- */
-static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
-{
- if (!ioc || ioc_batching(q, ioc))
- return;
-
- ioc->nr_batch_requests = q->nr_batching;
- ioc->last_waited = jiffies;
-}
-
static void __freed_request(struct request_queue *q, int sync)
{
struct request_list *rl = &q->rq;
@@ -670,7 +636,6 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
{
struct request *rq = NULL;
struct request_list *rl = &q->rq;
- struct io_context *ioc = NULL;
const bool is_sync = rw_is_sync(rw_flags) != 0;
int may_queue, priv;
@@ -679,30 +644,11 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
goto rq_starved;
if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
- if (rl->count[is_sync]+1 >= q->nr_requests) {
- ioc = current_io_context(GFP_ATOMIC, q->node);
- /*
- * The queue will fill after this allocation, so set
- * it as full, and mark this process as "batching".
- * This process will be allowed to complete a batch of
- * requests, others will be blocked.
- */
- if (!blk_queue_full(q, is_sync)) {
- ioc_set_batching(q, ioc);
- blk_set_queue_full(q, is_sync);
- } else {
- if (may_queue != ELV_MQUEUE_MUST
- && !ioc_batching(q, ioc)) {
- /*
- * The queue is full and the allocating
- * process is not a "batcher", and not
- * exempted by the IO scheduler
- */
- goto out;
- }
- }
- }
blk_set_queue_congested(q, is_sync);
+
+ if (rl->count[is_sync]+1 >= q->nr_requests)
+ if (may_queue != ELV_MQUEUE_MUST)
+ goto out;
}
/*
@@ -750,15 +696,6 @@ rq_starved:
goto out;
}
- /*
- * ioc may be NULL here, and ioc_batching will be false. That's
- * OK, if the queue is under the request limit then requests need
- * not count toward the nr_batch_requests limit. There will always
- * be some limit enforced by BLK_BATCH_TIME.
- */
- if (ioc_batching(q, ioc))
- ioc->nr_batch_requests--;
-
trace_block_getrq(q, bio, rw_flags & 1);
out:
return rq;
@@ -779,7 +716,6 @@ static struct request *get_request_wait(struct request_queue *q, int rw_flags,
rq = get_request(q, rw_flags, bio, GFP_NOIO);
while (!rq) {
DEFINE_WAIT(wait);
- struct io_context *ioc;
struct request_list *rl = &q->rq;
prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
@@ -790,15 +726,6 @@ static struct request *get_request_wait(struct request_queue *q, int rw_flags,
spin_unlock_irq(q->queue_lock);
io_schedule();
- /*
- * After sleeping, we become a "batching" process and
- * will be able to allocate at least one request, and
- * up to a big batch of them for a small period time.
- * See ioc_batching, ioc_set_batching
- */
- ioc = current_io_context(GFP_NOIO, q->node);
- ioc_set_batching(q, ioc);
-
spin_lock_irq(q->queue_lock);
finish_wait(&rl->wait[is_sync], &wait);
diff --git a/block/blk-settings.c b/block/blk-settings.c
index c8d6892..35420f2 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -162,7 +162,6 @@ void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
q->make_request_fn = mfn;
blk_queue_dma_alignment(q, 511);
blk_queue_congestion_threshold(q);
- q->nr_batching = BLK_BATCH_REQ;
blk_set_default_limits(&q->limits);
blk_queue_max_hw_sectors(q, BLK_SAFE_MAX_SECTORS);
diff --git a/block/blk.h b/block/blk.h
index 2c3d2e7..6db2e75 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -1,12 +1,6 @@
#ifndef BLK_INTERNAL_H
#define BLK_INTERNAL_H
-/* Amount of time in which a process may batch requests */
-#define BLK_BATCH_TIME (HZ/50UL)
-
-/* Number of requests a "batching" process may submit */
-#define BLK_BATCH_REQ 32
-
extern struct kmem_cache *blk_requestq_cachep;
extern struct kobj_type blk_queue_ktype;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index dfb6ffd..ebaf9d6 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -326,7 +326,6 @@ struct request_queue
unsigned long nr_requests; /* Max # of requests */
unsigned int nr_congestion_on;
unsigned int nr_congestion_off;
- unsigned int nr_batching;
void *dma_drain_buffer;
unsigned int dma_drain_size;
--
1.7.3.2.146.gca209
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