block: Adding ROW scheduling algorithm
This patch adds the implementation of a new scheduling algorithm - ROW.
The policy of this algorithm is to prioritize READ requests over WRITE
as much as possible without starving the WRITE requests.
Change-Id: I4ed52ea21d43b0e7c0769b2599779a3d3869c519
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
diff --git a/block/row-iosched.c b/block/row-iosched.c
new file mode 100644
index 0000000..f24437c
--- /dev/null
+++ b/block/row-iosched.c
@@ -0,0 +1,681 @@
+/*
+ * ROW (Read Over Write) I/O scheduler.
+ *
+ * Copyright (c) 2012, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+/* See Documentation/block/row-iosched.txt */
+
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/compiler.h>
+#include <linux/blktrace_api.h>
+#include <linux/jiffies.h>
+
+/*
+ * enum row_queue_prio - Priorities of the ROW queues
+ *
+ * This enum defines the priorities (and the number of queues)
+ * the requests will be disptributed to. The higher priority -
+ * the bigger is the dispatch quantum given to that queue.
+ * ROWQ_PRIO_HIGH_READ - is the higher priority queue.
+ *
+ */
+enum row_queue_prio {
+ ROWQ_PRIO_HIGH_READ = 0,
+ ROWQ_PRIO_REG_READ,
+ ROWQ_PRIO_HIGH_SWRITE,
+ ROWQ_PRIO_REG_SWRITE,
+ ROWQ_PRIO_REG_WRITE,
+ ROWQ_PRIO_LOW_READ,
+ ROWQ_PRIO_LOW_SWRITE,
+ ROWQ_MAX_PRIO,
+};
+
+/* Flags indicating whether idling is enabled on the queue */
+static const bool queue_idling_enabled[] = {
+ true, /* ROWQ_PRIO_HIGH_READ */
+ true, /* ROWQ_PRIO_REG_READ */
+ false, /* ROWQ_PRIO_HIGH_SWRITE */
+ false, /* ROWQ_PRIO_REG_SWRITE */
+ false, /* ROWQ_PRIO_REG_WRITE */
+ false, /* ROWQ_PRIO_LOW_READ */
+ false, /* ROWQ_PRIO_LOW_SWRITE */
+};
+
+/* Default values for row queues quantums in each dispatch cycle */
+static const int queue_quantum[] = {
+ 100, /* ROWQ_PRIO_HIGH_READ */
+ 100, /* ROWQ_PRIO_REG_READ */
+ 2, /* ROWQ_PRIO_HIGH_SWRITE */
+ 1, /* ROWQ_PRIO_REG_SWRITE */
+ 1, /* ROWQ_PRIO_REG_WRITE */
+ 1, /* ROWQ_PRIO_LOW_READ */
+ 1 /* ROWQ_PRIO_LOW_SWRITE */
+};
+
+/* Default values for idling on read queues */
+#define ROW_IDLE_TIME 50 /* 5 msec */
+#define ROW_READ_FREQ 70 /* 7 msec */
+
+/**
+ * struct rowq_idling_data - parameters for idling on the queue
+ * @idle_trigger_time: time (in jiffies). If a new request was
+ * inserted before this time value, idling
+ * will be enabled.
+ * @begin_idling: flag indicating wether we should idle
+ *
+ */
+struct rowq_idling_data {
+ unsigned long idle_trigger_time;
+ bool begin_idling;
+};
+
+/**
+ * struct row_queue - requests grouping structure
+ * @rdata: parent row_data structure
+ * @fifo: fifo of requests
+ * @prio: queue priority (enum row_queue_prio)
+ * @nr_dispatched: number of requests already dispatched in
+ * the current dispatch cycle
+ * @slice: number of requests to dispatch in a cycle
+ * @idle_data: data for idling on queues
+ *
+ */
+struct row_queue {
+ struct row_data *rdata;
+ struct list_head fifo;
+ enum row_queue_prio prio;
+
+ unsigned int nr_dispatched;
+ unsigned int slice;
+
+ /* used only for READ queues */
+ struct rowq_idling_data idle_data;
+};
+
+/**
+ * struct idling_data - data for idling on empty rqueue
+ * @idle_time: idling duration (msec)
+ * @freq: min time between two requests that
+ * triger idling (msec)
+ * @idle_work: pointer to struct delayed_work
+ *
+ */
+struct idling_data {
+ unsigned long idle_time;
+ unsigned long freq;
+
+ struct workqueue_struct *idle_workqueue;
+ struct delayed_work idle_work;
+};
+
+/**
+ * struct row_queue - Per block device rqueue structure
+ * @dispatch_queue: dispatch rqueue
+ * @row_queues: array of priority request queues with
+ * dispatch quantum per rqueue
+ * @curr_queue: index in the row_queues array of the
+ * currently serviced rqueue
+ * @read_idle: data for idling after READ request
+ * @nr_reqs: nr_reqs[0] holds the number of all READ requests in
+ * scheduler, nr_reqs[1] holds the number of all WRITE
+ * requests in scheduler
+ * @cycle_flags: used for marking unserved queueus
+ *
+ */
+struct row_data {
+ struct request_queue *dispatch_queue;
+
+ struct {
+ struct row_queue rqueue;
+ int disp_quantum;
+ } row_queues[ROWQ_MAX_PRIO];
+
+ enum row_queue_prio curr_queue;
+
+ struct idling_data read_idle;
+ unsigned int nr_reqs[2];
+
+ unsigned int cycle_flags;
+};
+
+#define RQ_ROWQ(rq) ((struct row_queue *) ((rq)->elv.priv[0]))
+
+#define row_log(q, fmt, args...) \
+ blk_add_trace_msg(q, "%s():" fmt , __func__, ##args)
+#define row_log_rowq(rdata, rowq_id, fmt, args...) \
+ blk_add_trace_msg(rdata->dispatch_queue, "rowq%d " fmt, \
+ rowq_id, ##args)
+
+static inline void row_mark_rowq_unserved(struct row_data *rd,
+ enum row_queue_prio qnum)
+{
+ rd->cycle_flags |= (1 << qnum);
+}
+
+static inline void row_clear_rowq_unserved(struct row_data *rd,
+ enum row_queue_prio qnum)
+{
+ rd->cycle_flags &= ~(1 << qnum);
+}
+
+static inline int row_rowq_unserved(struct row_data *rd,
+ enum row_queue_prio qnum)
+{
+ return rd->cycle_flags & (1 << qnum);
+}
+
+/******************** Static helper functions ***********************/
+/*
+ * kick_queue() - Wake up device driver queue thread
+ * @work: pointer to struct work_struct
+ *
+ * This is a idling delayed work function. It's purpose is to wake up the
+ * device driver in order for it to start fetching requests.
+ *
+ */
+static void kick_queue(struct work_struct *work)
+{
+ struct delayed_work *idle_work = to_delayed_work(work);
+ struct idling_data *read_data =
+ container_of(idle_work, struct idling_data, idle_work);
+ struct row_data *rd =
+ container_of(read_data, struct row_data, read_idle);
+
+ row_log_rowq(rd, rd->curr_queue, "Performing delayed work");
+ /* Mark idling process as done */
+ rd->row_queues[rd->curr_queue].rqueue.idle_data.begin_idling = false;
+
+ if (!(rd->nr_reqs[0] + rd->nr_reqs[1]))
+ row_log(rd->dispatch_queue, "No requests in scheduler");
+ else {
+ spin_lock_irq(rd->dispatch_queue->queue_lock);
+ __blk_run_queue(rd->dispatch_queue);
+ spin_unlock_irq(rd->dispatch_queue->queue_lock);
+ }
+}
+
+/*
+ * row_restart_disp_cycle() - Restart the dispatch cycle
+ * @rd: pointer to struct row_data
+ *
+ * This function restarts the dispatch cycle by:
+ * - Setting current queue to ROWQ_PRIO_HIGH_READ
+ * - For each queue: reset the number of requests dispatched in
+ * the cycle
+ */
+static inline void row_restart_disp_cycle(struct row_data *rd)
+{
+ int i;
+
+ for (i = 0; i < ROWQ_MAX_PRIO; i++)
+ rd->row_queues[i].rqueue.nr_dispatched = 0;
+
+ rd->curr_queue = ROWQ_PRIO_HIGH_READ;
+ row_log(rd->dispatch_queue, "Restarting cycle");
+}
+
+static inline void row_get_next_queue(struct row_data *rd)
+{
+ rd->curr_queue++;
+ if (rd->curr_queue == ROWQ_MAX_PRIO)
+ row_restart_disp_cycle(rd);
+}
+
+/******************* Elevator callback functions *********************/
+
+/*
+ * row_add_request() - Add request to the scheduler
+ * @q: requests queue
+ * @rq: request to add
+ *
+ */
+static void row_add_request(struct request_queue *q,
+ struct request *rq)
+{
+ struct row_data *rd = (struct row_data *)q->elevator->elevator_data;
+ struct row_queue *rqueue = RQ_ROWQ(rq);
+
+ list_add_tail(&rq->queuelist, &rqueue->fifo);
+ rd->nr_reqs[rq_data_dir(rq)]++;
+ rq_set_fifo_time(rq, jiffies); /* for statistics*/
+
+ if (queue_idling_enabled[rqueue->prio]) {
+ if (delayed_work_pending(&rd->read_idle.idle_work))
+ (void)cancel_delayed_work(
+ &rd->read_idle.idle_work);
+ if (time_before(jiffies, rqueue->idle_data.idle_trigger_time)) {
+ rqueue->idle_data.begin_idling = true;
+ row_log_rowq(rd, rqueue->prio, "Enable idling");
+ } else
+ rqueue->idle_data.begin_idling = false;
+
+ rqueue->idle_data.idle_trigger_time =
+ jiffies + msecs_to_jiffies(rd->read_idle.freq);
+ }
+ row_log_rowq(rd, rqueue->prio, "added request");
+}
+
+/*
+ * row_remove_request() - Remove given request from scheduler
+ * @q: requests queue
+ * @rq: request to remove
+ *
+ */
+static void row_remove_request(struct request_queue *q,
+ struct request *rq)
+{
+ struct row_data *rd = (struct row_data *)q->elevator->elevator_data;
+
+ rq_fifo_clear(rq);
+ rd->nr_reqs[rq_data_dir(rq)]--;
+}
+
+/*
+ * row_dispatch_insert() - move request to dispatch queue
+ * @rd: pointer to struct row_data
+ *
+ * This function moves the next request to dispatch from
+ * rd->curr_queue to the dispatch queue
+ *
+ */
+static void row_dispatch_insert(struct row_data *rd)
+{
+ struct request *rq;
+
+ rq = rq_entry_fifo(rd->row_queues[rd->curr_queue].rqueue.fifo.next);
+ row_remove_request(rd->dispatch_queue, rq);
+ elv_dispatch_add_tail(rd->dispatch_queue, rq);
+ rd->row_queues[rd->curr_queue].rqueue.nr_dispatched++;
+ row_clear_rowq_unserved(rd, rd->curr_queue);
+ row_log_rowq(rd, rd->curr_queue, " Dispatched request nr_disp = %d",
+ rd->row_queues[rd->curr_queue].rqueue.nr_dispatched);
+}
+
+/*
+ * row_choose_queue() - choose the next queue to dispatch from
+ * @rd: pointer to struct row_data
+ *
+ * Updates rd->curr_queue. Returns 1 if there are requests to
+ * dispatch, 0 if there are no requests in scheduler
+ *
+ */
+static int row_choose_queue(struct row_data *rd)
+{
+ int prev_curr_queue = rd->curr_queue;
+
+ if (!(rd->nr_reqs[0] + rd->nr_reqs[1])) {
+ row_log(rd->dispatch_queue, "No more requests in scheduler");
+ return 0;
+ }
+
+ row_get_next_queue(rd);
+
+ /*
+ * Loop over all queues to find the next queue that is not empty.
+ * Stop when you get back to curr_queue
+ */
+ while (list_empty(&rd->row_queues[rd->curr_queue].rqueue.fifo)
+ && rd->curr_queue != prev_curr_queue) {
+ /* Mark rqueue as unserved */
+ row_mark_rowq_unserved(rd, rd->curr_queue);
+ row_get_next_queue(rd);
+ }
+
+ return 1;
+}
+
+/*
+ * row_dispatch_requests() - selects the next request to dispatch
+ * @q: requests queue
+ * @force: ignored
+ *
+ * Return 0 if no requests were moved to the dispatch queue.
+ * 1 otherwise
+ *
+ */
+static int row_dispatch_requests(struct request_queue *q, int force)
+{
+ struct row_data *rd = (struct row_data *)q->elevator->elevator_data;
+ int ret = 0, currq, i;
+
+ currq = rd->curr_queue;
+
+ /*
+ * Find the first unserved queue (with higher priority then currq)
+ * that is not empty
+ */
+ for (i = 0; i < currq; i++) {
+ if (row_rowq_unserved(rd, i) &&
+ !list_empty(&rd->row_queues[i].rqueue.fifo)) {
+ row_log_rowq(rd, currq,
+ " Preemting for unserved rowq%d", i);
+ rd->curr_queue = i;
+ row_dispatch_insert(rd);
+ ret = 1;
+ goto done;
+ }
+ }
+
+ if (rd->row_queues[currq].rqueue.nr_dispatched >=
+ rd->row_queues[currq].disp_quantum) {
+ rd->row_queues[currq].rqueue.nr_dispatched = 0;
+ row_log_rowq(rd, currq, "Expiring rqueue");
+ ret = row_choose_queue(rd);
+ if (ret)
+ row_dispatch_insert(rd);
+ goto done;
+ }
+
+ /* Dispatch from curr_queue */
+ if (list_empty(&rd->row_queues[currq].rqueue.fifo)) {
+ /* check idling */
+ if (delayed_work_pending(&rd->read_idle.idle_work)) {
+ row_log_rowq(rd, currq,
+ "Delayed work pending. Exiting");
+ goto done;
+ }
+
+ if (queue_idling_enabled[currq] &&
+ rd->row_queues[currq].rqueue.idle_data.begin_idling) {
+ if (!queue_delayed_work(rd->read_idle.idle_workqueue,
+ &rd->read_idle.idle_work,
+ jiffies +
+ msecs_to_jiffies(rd->read_idle.idle_time))) {
+ row_log_rowq(rd, currq,
+ "Work already on queue!");
+ pr_err("ROW_BUG: Work already on queue!");
+ } else
+ row_log_rowq(rd, currq,
+ "Scheduled delayed work. exiting");
+ goto done;
+ } else {
+ row_log_rowq(rd, currq,
+ "Currq empty. Choose next queue");
+ ret = row_choose_queue(rd);
+ if (!ret)
+ goto done;
+ }
+ }
+
+ ret = 1;
+ row_dispatch_insert(rd);
+
+done:
+ return ret;
+}
+
+/*
+ * row_init_queue() - Init scheduler data structures
+ * @q: requests queue
+ *
+ * Return pointer to struct row_data to be saved in elevator for
+ * this dispatch queue
+ *
+ */
+static void *row_init_queue(struct request_queue *q)
+{
+
+ struct row_data *rdata;
+ int i;
+
+ rdata = kmalloc_node(sizeof(*rdata),
+ GFP_KERNEL | __GFP_ZERO, q->node);
+ if (!rdata)
+ return NULL;
+
+ for (i = 0; i < ROWQ_MAX_PRIO; i++) {
+ INIT_LIST_HEAD(&rdata->row_queues[i].rqueue.fifo);
+ rdata->row_queues[i].disp_quantum = queue_quantum[i];
+ rdata->row_queues[i].rqueue.rdata = rdata;
+ rdata->row_queues[i].rqueue.prio = i;
+ rdata->row_queues[i].rqueue.idle_data.begin_idling = false;
+ }
+
+ /*
+ * Currently idling is enabled only for READ queues. If we want to
+ * enable it for write queues also, note that idling frequency will
+ * be the same in both cases
+ */
+ rdata->read_idle.idle_time = ROW_IDLE_TIME;
+ rdata->read_idle.freq = ROW_READ_FREQ;
+ rdata->read_idle.idle_workqueue = alloc_workqueue("row_idle_work",
+ WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
+ if (!rdata->read_idle.idle_workqueue)
+ panic("Failed to create idle workqueue\n");
+ INIT_DELAYED_WORK(&rdata->read_idle.idle_work, kick_queue);
+
+ rdata->curr_queue = ROWQ_PRIO_HIGH_READ;
+ rdata->dispatch_queue = q;
+
+ rdata->nr_reqs[READ] = rdata->nr_reqs[WRITE] = 0;
+
+ return rdata;
+}
+
+/*
+ * row_exit_queue() - called on unloading the RAW scheduler
+ * @e: poiner to struct elevator_queue
+ *
+ */
+static void row_exit_queue(struct elevator_queue *e)
+{
+ struct row_data *rd = (struct row_data *)e->elevator_data;
+ int i;
+
+ for (i = 0; i < ROWQ_MAX_PRIO; i++)
+ BUG_ON(!list_empty(&rd->row_queues[i].rqueue.fifo));
+ (void)cancel_delayed_work_sync(&rd->read_idle.idle_work);
+ kfree(rd);
+}
+
+/*
+ * row_merged_requests() - Called when 2 requests are merged
+ * @q: requests queue
+ * @rq: request the two requests were merged into
+ * @next: request that was merged
+ */
+static void row_merged_requests(struct request_queue *q, struct request *rq,
+ struct request *next)
+{
+ struct row_queue *rqueue = RQ_ROWQ(next);
+
+ list_del_init(&next->queuelist);
+
+ rqueue->rdata->nr_reqs[rq_data_dir(rq)]--;
+}
+
+/*
+ * get_queue_type() - Get queue type for a given request
+ *
+ * This is a helping function which purpose is to determine what
+ * ROW queue the given request should be added to (and
+ * dispatched from leter on)
+ *
+ * TODO: Right now only 3 queues are used REG_READ, REG_WRITE
+ * and REG_SWRITE
+ */
+static enum row_queue_prio get_queue_type(struct request *rq)
+{
+ const int data_dir = rq_data_dir(rq);
+ const bool is_sync = rq_is_sync(rq);
+
+ if (data_dir == READ)
+ return ROWQ_PRIO_REG_READ;
+ else if (is_sync)
+ return ROWQ_PRIO_REG_SWRITE;
+ else
+ return ROWQ_PRIO_REG_WRITE;
+}
+
+/*
+ * row_set_request() - Set ROW data structures associated with this request.
+ * @q: requests queue
+ * @rq: pointer to the request
+ * @gfp_mask: ignored
+ *
+ */
+static int
+row_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
+{
+ struct row_data *rd = (struct row_data *)q->elevator->elevator_data;
+ unsigned long flags;
+
+ spin_lock_irqsave(q->queue_lock, flags);
+ rq->elv.priv[0] =
+ (void *)(&rd->row_queues[get_queue_type(rq)]);
+ spin_unlock_irqrestore(q->queue_lock, flags);
+
+ return 0;
+}
+
+/********** Helping sysfs functions/defenitions for ROW attributes ******/
+static ssize_t row_var_show(int var, char *page)
+{
+ return snprintf(page, 100, "%d\n", var);
+}
+
+static ssize_t row_var_store(int *var, const char *page, size_t count)
+{
+ int err;
+ err = kstrtoul(page, 10, (unsigned long *)var);
+
+ return count;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
+static ssize_t __FUNC(struct elevator_queue *e, char *page) \
+{ \
+ struct row_data *rowd = e->elevator_data; \
+ int __data = __VAR; \
+ if (__CONV) \
+ __data = jiffies_to_msecs(__data); \
+ return row_var_show(__data, (page)); \
+}
+SHOW_FUNCTION(row_hp_read_quantum_show,
+ rowd->row_queues[ROWQ_PRIO_HIGH_READ].disp_quantum, 0);
+SHOW_FUNCTION(row_rp_read_quantum_show,
+ rowd->row_queues[ROWQ_PRIO_REG_READ].disp_quantum, 0);
+SHOW_FUNCTION(row_hp_swrite_quantum_show,
+ rowd->row_queues[ROWQ_PRIO_HIGH_SWRITE].disp_quantum, 0);
+SHOW_FUNCTION(row_rp_swrite_quantum_show,
+ rowd->row_queues[ROWQ_PRIO_REG_SWRITE].disp_quantum, 0);
+SHOW_FUNCTION(row_rp_write_quantum_show,
+ rowd->row_queues[ROWQ_PRIO_REG_WRITE].disp_quantum, 0);
+SHOW_FUNCTION(row_lp_read_quantum_show,
+ rowd->row_queues[ROWQ_PRIO_LOW_READ].disp_quantum, 0);
+SHOW_FUNCTION(row_lp_swrite_quantum_show,
+ rowd->row_queues[ROWQ_PRIO_LOW_SWRITE].disp_quantum, 0);
+SHOW_FUNCTION(row_read_idle_show, rowd->read_idle.idle_time, 1);
+SHOW_FUNCTION(row_read_idle_freq_show, rowd->read_idle.freq, 1);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
+static ssize_t __FUNC(struct elevator_queue *e, \
+ const char *page, size_t count) \
+{ \
+ struct row_data *rowd = e->elevator_data; \
+ int __data; \
+ int ret = row_var_store(&__data, (page), count); \
+ if (__CONV) \
+ __data = (int)msecs_to_jiffies(__data); \
+ if (__data < (MIN)) \
+ __data = (MIN); \
+ else if (__data > (MAX)) \
+ __data = (MAX); \
+ *(__PTR) = __data; \
+ return ret; \
+}
+STORE_FUNCTION(row_hp_read_quantum_store,
+ &rowd->row_queues[ROWQ_PRIO_HIGH_READ].disp_quantum, 0,
+ INT_MAX, 0);
+STORE_FUNCTION(row_rp_read_quantum_store,
+ &rowd->row_queues[ROWQ_PRIO_REG_READ].disp_quantum, 0,
+ INT_MAX, 0);
+STORE_FUNCTION(row_hp_swrite_quantum_store,
+ &rowd->row_queues[ROWQ_PRIO_HIGH_SWRITE].disp_quantum, 0,
+ INT_MAX, 0);
+STORE_FUNCTION(row_rp_swrite_quantum_store,
+ &rowd->row_queues[ROWQ_PRIO_REG_SWRITE].disp_quantum, 0,
+ INT_MAX, 0);
+STORE_FUNCTION(row_rp_write_quantum_store,
+ &rowd->row_queues[ROWQ_PRIO_REG_WRITE].disp_quantum, 0,
+ INT_MAX, 0);
+STORE_FUNCTION(row_lp_read_quantum_store,
+ &rowd->row_queues[ROWQ_PRIO_LOW_READ].disp_quantum, 0,
+ INT_MAX, 0);
+STORE_FUNCTION(row_lp_swrite_quantum_store,
+ &rowd->row_queues[ROWQ_PRIO_LOW_SWRITE].disp_quantum, 0,
+ INT_MAX, 1);
+STORE_FUNCTION(row_read_idle_store, &rowd->read_idle.idle_time, 1, INT_MAX, 1);
+STORE_FUNCTION(row_read_idle_freq_store, &rowd->read_idle.freq,
+ 1, INT_MAX, 1);
+
+#undef STORE_FUNCTION
+
+#define ROW_ATTR(name) \
+ __ATTR(name, S_IRUGO|S_IWUSR, row_##name##_show, \
+ row_##name##_store)
+
+static struct elv_fs_entry row_attrs[] = {
+ ROW_ATTR(hp_read_quantum),
+ ROW_ATTR(rp_read_quantum),
+ ROW_ATTR(hp_swrite_quantum),
+ ROW_ATTR(rp_swrite_quantum),
+ ROW_ATTR(rp_write_quantum),
+ ROW_ATTR(lp_read_quantum),
+ ROW_ATTR(lp_swrite_quantum),
+ ROW_ATTR(read_idle),
+ ROW_ATTR(read_idle_freq),
+ __ATTR_NULL
+};
+
+static struct elevator_type iosched_row = {
+ .ops = {
+ .elevator_merge_req_fn = row_merged_requests,
+ .elevator_dispatch_fn = row_dispatch_requests,
+ .elevator_add_req_fn = row_add_request,
+ .elevator_former_req_fn = elv_rb_former_request,
+ .elevator_latter_req_fn = elv_rb_latter_request,
+ .elevator_set_req_fn = row_set_request,
+ .elevator_init_fn = row_init_queue,
+ .elevator_exit_fn = row_exit_queue,
+ },
+
+ .elevator_attrs = row_attrs,
+ .elevator_name = "row",
+ .elevator_owner = THIS_MODULE,
+};
+
+static int __init row_init(void)
+{
+ elv_register(&iosched_row);
+ return 0;
+}
+
+static void __exit row_exit(void)
+{
+ elv_unregister(&iosched_row);
+}
+
+module_init(row_init);
+module_exit(row_exit);
+
+MODULE_LICENSE("GPLv2");
+MODULE_DESCRIPTION("Read Over Write IO scheduler");