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Commit 4050cf16 authored by Jens Axboe's avatar Jens Axboe Committed by Jens Axboe
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[PATCH] cfq-iosched: use new io context counting mechanism 



It's ok if the read path is a lot more costly, as long as inc/dec is
really cheap. The inc/dec will happen for each created/freed io context,
while the reading only happens when a disk queue exits.

Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent e4313dd4

block/cfq-iosched.c

+7 −5
Original line number Diff line number Diff line
@@ -46,7 +46,7 @@ static int cfq_slice_idle = HZ / 125; 
static kmem_cache_t *cfq_pool;

static kmem_cache_t *cfq_ioc_pool;



static atomic_t ioc_count = ATOMIC_INIT(0);

static DEFINE_PER_CPU(unsigned long, ioc_count);

static struct completion *ioc_gone;



#define CFQ_PRIO_LISTS		IOPRIO_BE_NR
@@ -1078,7 +1078,9 @@ static void cfq_free_io_context(struct io_context *ioc) 
		freed++;

	}



	if (atomic_sub_and_test(freed, &ioc_count) && ioc_gone)

	elv_ioc_count_mod(ioc_count, -freed);



	if (ioc_gone && !elv_ioc_count_read(ioc_count))

		complete(ioc_gone);

}
@@ -1154,7 +1156,7 @@ cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 
		INIT_LIST_HEAD(&cic->queue_list);

		cic->dtor = cfq_free_io_context;

		cic->exit = cfq_exit_io_context;

		atomic_inc(&ioc_count);

		elv_ioc_count_inc(ioc_count);

	}



	return cic;
@@ -1319,7 +1321,7 @@ cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic) 
	WARN_ON(!list_empty(&cic->queue_list));

	rb_erase(&cic->rb_node, &ioc->cic_root);

	kmem_cache_free(cfq_ioc_pool, cic);

	atomic_dec(&ioc_count);

	elv_ioc_count_dec(ioc_count);

}



static struct cfq_io_context *
@@ -2165,7 +2167,7 @@ static void __exit cfq_exit(void) 
	ioc_gone = &all_gone;

	/* ioc_gone's update must be visible before reading ioc_count */

	smp_wmb();

	if (atomic_read(&ioc_count))

	if (elv_ioc_count_read(ioc_count))

		wait_for_completion(ioc_gone);

	synchronize_rcu();

	cfq_slab_kill();