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[PATCH] cfq-iosched: use new io context counting mechanism

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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: Jens Axboe <axboe@suse.de>
This commit is contained in:
Jens Axboe 2006-07-19 05:07:12 +02:00 committed by Jens Axboe
parent e4313dd423
commit 4050cf1674
1 changed files with 7 additions and 5 deletions
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12
block/cfq-iosched.c
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@ -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();