--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -62,6 +62,14 @@ config CGROUP_BFQIO
filesystem interface. The name of the subsystem will be
bfqio.
+config IOSCHED_VR
+ tristate "V(R) I/O scheduler"
+ default y
+ ---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
@@ -81,6 +89,9 @@ choice
config DEFAULT_BFQ
bool "BFQ" if IOSCHED_BFQ=y
+ config DEFAULT_VR
+ bool "V(R)" if IOSCHED_VR=y
+
config DEFAULT_NOOP
bool "No-op"
@@ -93,6 +104,7 @@ config DEFAULT_IOSCHED
default "cfq" if DEFAULT_CFQ
default "bfq" if DEFAULT_BFQ
default "noop" if DEFAULT_NOOP
+ default "vr" if DEFAULT_VR
endmenu
--- a/block/Makefile
+++ b/block/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_IOSCHED_AS) += as-iosched.o
obj-$(CONFIG_IOSCHED_DEADLINE) += deadline-iosched.o
obj-$(CONFIG_IOSCHED_CFQ) += cfq-iosched.o
obj-$(CONFIG_IOSCHED_BFQ) += bfq-iosched.o
+obj-$(CONFIG_IOSCHED_VR) += vr-iosched.o
obj-$(CONFIG_BLOCK_COMPAT) += compat_ioctl.o
obj-$(CONFIG_BLK_DEV_INTEGRITY) += blk-integrity.o
--- /dev/null
+++ b/block/vr-iosched.c
@@ -0,0 +1,446 @@
+/*
+ * 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 <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 = 16;
+static const int rev_penalty = 10; /* 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;
+}
+
+static int
+vr_queue_empty(struct request_queue *q)
+{
+ struct vr_data *vd = vr_get_data(q);
+ return RB_EMPTY_ROOT(&vd->sort_list);
+}
+
+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,
+ .elevator_queue_empty_fn = vr_queue_empty,
+ .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-frankenstein-kernel.git / commitdiff