--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -43,6 +43,13 @@ config CFQ_GROUP_IOSCHED
---help---
Enable group IO scheduling in CFQ.
+config IOSCHED_VR
+ tristate "V(R) I/O scheduler"
+ default n
+ ---help---
+ Requests are chosen according to SSTF with a penalty of rev_penalty
+ for switching head direction.
+
choice
prompt "Default I/O scheduler"
default DEFAULT_CFQ
@@ -56,6 +63,9 @@ choice
config DEFAULT_CFQ
bool "CFQ" if IOSCHED_CFQ=y
+ config DEFAULT_VR
+ bool "V(R)" if IOSCHED_VR=y
+
config DEFAULT_NOOP
bool "No-op"
@@ -65,6 +75,7 @@ config DEFAULT_IOSCHED
string
default "deadline" if DEFAULT_DEADLINE
default "cfq" if DEFAULT_CFQ
+ default "vr" if DEFAULT_VR
default "noop" if DEFAULT_NOOP
endmenu
--- /dev/null
+++ b/block/vr-iosched.c
@@ -0,0 +1,453 @@
+/*
+* V(R) I/O Scheduler
+*
+* Copyright (C) 2007 Aaron Carroll <aaronc@gelato.unsw.edu.au>
+*
+*
+* The algorithm:
+*
+* The next request is decided based on its distance from the last
+* request, with a multiplicative penalty of `rev_penalty' applied
+* for reversing the head direction. A rev_penalty of 1 means SSTF
+* behaviour. As this variable is increased, the algorithm approaches
+* pure SCAN. Setting rev_penalty to 0 forces SCAN.
+*
+* Async and synch requests are not treated seperately. Instead we
+* rely on deadlines to ensure fairness.
+*
+*/
+#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/rbtree.h>
+#include <linux/version.h>
+
+#include <asm/div64.h>
+
+enum vr_data_dir {
+ASYNC,
+SYNC,
+};
+
+enum vr_head_dir {
+FORWARD,
+BACKWARD,
+};
+
+static const int sync_expire = HZ / 2; /* max time before a sync is submitted. */
+static const int async_expire = 5 * HZ; /* ditto for async, these limits are SOFT! */
+static const int fifo_batch = 1;
+static const int rev_penalty = 1; /* penalty for reversing head direction */
+
+struct vr_data {
+struct rb_root sort_list;
+struct list_head fifo_list[2];
+
+struct request *next_rq;
+struct request *prev_rq;
+
+unsigned int nbatched;
+sector_t last_sector; /* head position */
+int head_dir;
+
+/* tunables */
+int fifo_expire[2];
+int fifo_batch;
+int rev_penalty;
+};
+
+static void vr_move_request(struct vr_data *, struct request *);
+
+static inline struct vr_data *
+vr_get_data(struct request_queue *q)
+{
+return q->elevator->elevator_data;
+}
+
+static void
+vr_add_rq_rb(struct vr_data *vd, struct request *rq)
+{
+struct request *alias = elv_rb_add(&vd->sort_list, rq);
+
+if (unlikely(alias)) {
+vr_move_request(vd, alias);
+alias = elv_rb_add(&vd->sort_list, rq);
+BUG_ON(alias);
+}
+
+if (blk_rq_pos(rq) >= vd->last_sector) {
+if (!vd->next_rq || blk_rq_pos(vd->next_rq) > blk_rq_pos(rq))
+vd->next_rq = rq;
+}
+else {
+if (!vd->prev_rq || blk_rq_pos(vd->prev_rq) < blk_rq_pos(rq))
+vd->prev_rq = rq;
+}
+
+BUG_ON(vd->next_rq && vd->next_rq == vd->prev_rq);
+BUG_ON(vd->next_rq && vd->prev_rq && blk_rq_pos(vd->next_rq) < blk_rq_pos(vd->prev_rq));
+}
+
+static void
+vr_del_rq_rb(struct vr_data *vd, struct request *rq)
+{
+/*
+* We might be deleting our cached next request.
+* If so, find its sucessor.
+*/
+
+if (vd->next_rq == rq)
+vd->next_rq = elv_rb_latter_request(NULL, rq);
+else if (vd->prev_rq == rq)
+vd->prev_rq = elv_rb_former_request(NULL, rq);
+
+BUG_ON(vd->next_rq && vd->next_rq == vd->prev_rq);
+BUG_ON(vd->next_rq && vd->prev_rq && blk_rq_pos(vd->next_rq) < blk_rq_pos(vd->prev_rq));
+
+elv_rb_del(&vd->sort_list, rq);
+}
+
+/*
+* add rq to rbtree and fifo
+*/
+static void
+vr_add_request(struct request_queue *q, struct request *rq)
+{
+struct vr_data *vd = vr_get_data(q);
+const int dir = rq_is_sync(rq);
+
+vr_add_rq_rb(vd, rq);
+
+if (vd->fifo_expire[dir]) {
+rq_set_fifo_time(rq, jiffies + vd->fifo_expire[dir]);
+list_add_tail(&rq->queuelist, &vd->fifo_list[dir]);
+}
+}
+
+/*
+* remove rq from rbtree and fifo.
+*/
+static void
+vr_remove_request(struct request_queue *q, struct request *rq)
+{
+struct vr_data *vd = vr_get_data(q);
+
+rq_fifo_clear(rq);
+vr_del_rq_rb(vd, rq);
+}
+
+static int
+vr_merge(struct request_queue *q, struct request **rqp, struct bio *bio)
+{
+sector_t sector = bio->bi_sector + bio_sectors(bio);
+struct vr_data *vd = vr_get_data(q);
+struct request *rq = elv_rb_find(&vd->sort_list, sector);
+
+if (rq && elv_rq_merge_ok(rq, bio)) {
+*rqp = rq;
+return ELEVATOR_FRONT_MERGE;
+}
+return ELEVATOR_NO_MERGE;
+}
+
+static void
+vr_merged_request(struct request_queue *q, struct request *req, int type)
+{
+struct vr_data *vd = vr_get_data(q);
+
+/*
+* if the merge was a front merge, we need to reposition request
+*/
+if (type == ELEVATOR_FRONT_MERGE) {
+vr_del_rq_rb(vd, req);
+vr_add_rq_rb(vd, req);
+}
+}
+
+static void
+vr_merged_requests(struct request_queue *q, struct request *rq,
+struct request *next)
+{
+/*
+* if next expires before rq, assign its expire time to rq
+* and move into next position (next will be deleted) in fifo
+*/
+if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist)) {
+if (time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
+list_move(&rq->queuelist, &next->queuelist);
+rq_set_fifo_time(rq, rq_fifo_time(next));
+}
+}
+
+vr_remove_request(q, next);
+}
+
+/*
+* move an entry to dispatch queue
+*/
+static void
+vr_move_request(struct vr_data *vd, struct request *rq)
+{
+struct request_queue *q = rq->q;
+
+if (blk_rq_pos(rq) > vd->last_sector)
+vd->head_dir = FORWARD;
+else
+vd->head_dir = BACKWARD;
+
+vd->last_sector = blk_rq_pos(rq);
+vd->next_rq = elv_rb_latter_request(NULL, rq);
+vd->prev_rq = elv_rb_former_request(NULL, rq);
+
+BUG_ON(vd->next_rq && vd->next_rq == vd->prev_rq);
+
+vr_remove_request(q, rq);
+elv_dispatch_add_tail(q, rq);
+vd->nbatched++;
+}
+
+/*
+* get the first expired request in direction ddir
+*/
+static struct request *
+vr_expired_request(struct vr_data *vd, int ddir)
+{
+struct request *rq;
+
+if (list_empty(&vd->fifo_list[ddir]))
+return NULL;
+
+rq = rq_entry_fifo(vd->fifo_list[ddir].next);
+if (time_after(jiffies, rq_fifo_time(rq)))
+return rq;
+
+return NULL;
+}
+
+/*
+* Returns the oldest expired request
+*/
+static struct request *
+vr_check_fifo(struct vr_data *vd)
+{
+struct request *rq_sync = vr_expired_request(vd, SYNC);
+struct request *rq_async = vr_expired_request(vd, ASYNC);
+
+if (rq_async && rq_sync) {
+if (time_after(rq_fifo_time(rq_async), rq_fifo_time(rq_sync)))
+return rq_sync;
+}
+else if (rq_sync)
+return rq_sync;
+
+return rq_async;
+}
+
+/*
+* Return the request with the lowest penalty
+*/
+static struct request *
+vr_choose_request(struct vr_data *vd)
+{
+int penalty = (vd->rev_penalty) ? : INT_MAX;
+struct request *next = vd->next_rq;
+struct request *prev = vd->prev_rq;
+sector_t next_pen, prev_pen;
+
+BUG_ON(prev && prev == next);
+
+if (!prev)
+return next;
+else if (!next)
+return prev;
+
+/* At this point both prev and next are defined and distinct */
+
+next_pen = blk_rq_pos(next) - vd->last_sector;
+prev_pen = vd->last_sector - blk_rq_pos(prev);
+
+if (vd->head_dir == FORWARD)
+next_pen = do_div(next_pen, penalty);
+else
+prev_pen = do_div(prev_pen, penalty);
+
+if (next_pen <= prev_pen)
+return next;
+
+return prev;
+}
+
+static int
+vr_dispatch_requests(struct request_queue *q, int force)
+{
+struct vr_data *vd = vr_get_data(q);
+struct request *rq = NULL;
+
+/* Check for and issue expired requests */
+if (vd->nbatched > vd->fifo_batch) {
+vd->nbatched = 0;
+rq = vr_check_fifo(vd);
+}
+
+if (!rq) {
+rq = vr_choose_request(vd);
+if (!rq)
+return 0;
+}
+
+vr_move_request(vd, rq);
+
+return 1;
+}
+
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,38)
+static int
+vr_queue_empty(struct request_queue *q)
+{
+struct vr_data *vd = vr_get_data(q);
+return RB_EMPTY_ROOT(&vd->sort_list);
+}
+#endif
+
+static void
+vr_exit_queue(struct elevator_queue *e)
+{
+struct vr_data *vd = e->elevator_data;
+BUG_ON(!RB_EMPTY_ROOT(&vd->sort_list));
+kfree(vd);
+}
+
+/*
+* initialize elevator private data (vr_data).
+*/
+static void *vr_init_queue(struct request_queue *q)
+{
+struct vr_data *vd;
+
+vd = kmalloc_node(sizeof(*vd), GFP_KERNEL | __GFP_ZERO, q->node);
+if (!vd)
+return NULL;
+
+INIT_LIST_HEAD(&vd->fifo_list[SYNC]);
+INIT_LIST_HEAD(&vd->fifo_list[ASYNC]);
+vd->sort_list = RB_ROOT;
+vd->fifo_expire[SYNC] = sync_expire;
+vd->fifo_expire[ASYNC] = async_expire;
+vd->fifo_batch = fifo_batch;
+vd->rev_penalty = rev_penalty;
+return vd;
+}
+
+/*
+* sysfs parts below
+*/
+
+static ssize_t
+vr_var_show(int var, char *page)
+{
+return sprintf(page, "%d\n", var);
+}
+
+static ssize_t
+vr_var_store(int *var, const char *page, size_t count)
+{
+*var = simple_strtol(page, NULL, 10);
+return count;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
+static ssize_t __FUNC(struct elevator_queue *e, char *page) \
+{ \
+struct vr_data *vd = e->elevator_data; \
+int __data = __VAR; \
+if (__CONV) \
+__data = jiffies_to_msecs(__data); \
+return vr_var_show(__data, (page)); \
+}
+SHOW_FUNCTION(vr_sync_expire_show, vd->fifo_expire[SYNC], 1);
+SHOW_FUNCTION(vr_async_expire_show, vd->fifo_expire[ASYNC], 1);
+SHOW_FUNCTION(vr_fifo_batch_show, vd->fifo_batch, 0);
+SHOW_FUNCTION(vr_rev_penalty_show, vd->rev_penalty, 0);
+#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 vr_data *vd = e->elevator_data; \
+int __data; \
+int ret = vr_var_store(&__data, (page), count); \
+if (__data < (MIN)) \
+__data = (MIN); \
+else if (__data > (MAX)) \
+__data = (MAX); \
+if (__CONV) \
+*(__PTR) = msecs_to_jiffies(__data); \
+else \
+*(__PTR) = __data; \
+return ret; \
+}
+STORE_FUNCTION(vr_sync_expire_store, &vd->fifo_expire[SYNC], 0, INT_MAX, 1);
+STORE_FUNCTION(vr_async_expire_store, &vd->fifo_expire[ASYNC], 0, INT_MAX, 1);
+STORE_FUNCTION(vr_fifo_batch_store, &vd->fifo_batch, 0, INT_MAX, 0);
+STORE_FUNCTION(vr_rev_penalty_store, &vd->rev_penalty, 0, INT_MAX, 0);
+#undef STORE_FUNCTION
+
+#define DD_ATTR(name) \
+__ATTR(name, S_IRUGO|S_IWUSR, vr_##name##_show, \
+vr_##name##_store)
+
+static struct elv_fs_entry vr_attrs[] = {
+DD_ATTR(sync_expire),
+DD_ATTR(async_expire),
+DD_ATTR(fifo_batch),
+DD_ATTR(rev_penalty),
+__ATTR_NULL
+};
+
+static struct elevator_type iosched_vr = {
+.ops = {
+.elevator_merge_fn = vr_merge,
+.elevator_merged_fn = vr_merged_request,
+.elevator_merge_req_fn = vr_merged_requests,
+.elevator_dispatch_fn = vr_dispatch_requests,
+.elevator_add_req_fn = vr_add_request,
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,38)
+.elevator_queue_empty_fn = vr_queue_empty,
+#endif
+.elevator_former_req_fn = elv_rb_former_request,
+.elevator_latter_req_fn = elv_rb_latter_request,
+.elevator_init_fn = vr_init_queue,
+.elevator_exit_fn = vr_exit_queue,
+},
+
+.elevator_attrs = vr_attrs,
+.elevator_name = "vr",
+.elevator_owner = THIS_MODULE,
+};
+
+static int __init vr_init(void)
+{
+elv_register(&iosched_vr);
+
+return 0;
+}
+
+static void __exit vr_exit(void)
+{
+elv_unregister(&iosched_vr);
+}
+
+module_init(vr_init);
+module_exit(vr_exit);
+
+MODULE_AUTHOR("Aaron Carroll");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("V(R) IO scheduler");
+
+
projects / ziggy471-sgn2-jb.git / commitdiff