[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: Jens Axboe <axboe@suse.de>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 33e0b0c..c988aa7 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -46,7 +46,7 @@
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 @@
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 @@
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 @@
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 @@
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();