/*
 * tunables
 */
static const int cfq_quantum = 4;		/* max queue in one round of service */
static const int cfq_queued = 8;		/* minimum rq allocate limit per-queue*/
static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
static const int cfq_back_max = 16 * 1024;	/* maximum backwards seek, in KiB */
static const int cfq_back_penalty = 2;		/* penalty of a backwards seek */

static const int cfq_slice_sync = HZ / 10;
static int cfq_slice_async = HZ / 25;
static const int cfq_slice_async_rq = 2;
static int cfq_slice_idle = HZ / 125;

#define CFQ_IDLE_GRACE		(HZ / 10)
#define CFQ_SLICE_SCALE		(5)

#define CFQ_KEY_ASYNC		(0)

static DEFINE_SPINLOCK(cfq_exit_lock);