--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -50,6 +50,16 @@ config IOSCHED_VR
Requests are chosen according to SSTF with a penalty of rev_penalty
for switching head direction.
+config IOSCHED_SIO
+ tristate "Simple I/O scheduler"
+ default y
+ ---help---
+ The Simple I/O scheduler is an extremely simple scheduler,
+ based on noop and deadline, that relies on deadlines to
+ ensure fairness. The algorithm does not do any sorting but
+ basic merging, trying to keep a minimum overhead. It is aimed
+ mainly for aleatory access devices (eg: flash devices).
+
choice
prompt "Default I/O scheduler"
default DEFAULT_CFQ
@@ -63,6 +73,9 @@ choice
config DEFAULT_CFQ
bool "CFQ" if IOSCHED_CFQ=y
+ config DEFAULT_SIO
+ bool "SIO" if IOSCHED_SIO=y
+
config DEFAULT_VR
bool "V(R)" if IOSCHED_VR=y
@@ -75,6 +88,7 @@ config DEFAULT_IOSCHED
string
default "deadline" if DEFAULT_DEADLINE
default "cfq" if DEFAULT_CFQ
+ default "sio" if DEFAULT_SIO
default "vr" if DEFAULT_VR
default "noop" if DEFAULT_NOOP
--- a/block/Makefile
+++ b/block/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_BLK_DEV_THROTTLING) += blk-
obj-$(CONFIG_IOSCHED_NOOP) += noop-iosched.o
obj-$(CONFIG_IOSCHED_DEADLINE) += deadline-iosched.o
obj-$(CONFIG_IOSCHED_CFQ) += cfq-iosched.o
+obj-$(CONFIG_IOSCHED_SIO) += sio-iosched.o
obj-$(CONFIG_IOSCHED_VR) += vr-iosched.o
obj-$(CONFIG_BLOCK_COMPAT) += compat_ioctl.o
--- /dev/null
+++ b/block/sio-iosched.c
@@ -0,0 +1,399 @@
+/*
+ * Simple IO scheduler
+ * Based on Noop, Deadline and V(R) IO schedulers.
+ *
+ * Copyright (C) 2012 Miguel Boton <mboton@gmail.com>
+ *
+ *
+ * This algorithm does not do any kind of sorting, as it is aimed for
+ * aleatory access devices, but it does some basic merging. We try to
+ * keep minimum overhead to achieve low latency.
+ *
+ * Asynchronous and synchronous requests are not treated separately, but
+ * we relay on deadlines to ensure fairness.
+ *
+ */
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/version.h>
+
+enum { ASYNC, SYNC };
+
+/* Tunables */
+static const int sync_read_expire = HZ / 8; /* max time before a sync read is submitted. */
+static const int sync_write_expire = 2 * HZ; /* max time before a sync write is submitted. */
+
+static const int async_read_expire = HZ / 8; /* ditto for async, these limits are SOFT! */
+static const int async_write_expire = 2 * HZ; /* ditto for async, these limits are SOFT! */
+
+static const int writes_starved = 2; /* max times reads can starve a write */
+static const int fifo_batch = 8; /* # of sequential requests treated as one
+ by the above parameters. For throughput. */
+
+/* Elevator data */
+struct sio_data {
+ /* Request queues */
+ struct list_head fifo_list[2][2];
+
+ /* Attributes */
+ unsigned int batched;
+ unsigned int starved;
+
+ /* Settings */
+ int fifo_expire[2][2];
+ int fifo_batch;
+ int writes_starved;
+};
+
+static void
+sio_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));
+ }
+ }
+
+ /* Delete next request */
+ rq_fifo_clear(next);
+}
+
+static void
+sio_add_request(struct request_queue *q, struct request *rq)
+{
+ struct sio_data *sd = q->elevator->elevator_data;
+ const int sync = rq_is_sync(rq);
+ const int data_dir = rq_data_dir(rq);
+
+ /*
+ * Add request to the proper fifo list and set its
+ * expire time.
+ */
+ rq_set_fifo_time(rq, jiffies + sd->fifo_expire[sync][data_dir]);
+ list_add_tail(&rq->queuelist, &sd->fifo_list[sync][data_dir]);
+}
+
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,38)
+static int
+sio_queue_empty(struct request_queue *q)
+{
+ struct sio_data *sd = q->elevator->elevator_data;
+
+ /* Check if fifo lists are empty */
+ return list_empty(&sd->fifo_list[SYNC][READ]) && list_empty(&sd->fifo_list[SYNC][WRITE])
+ list_empty(&sd->fifo_list[ASYNC][READ]) && list_empty(&sd->fifo_list[ASYNC][WRITE]);
+}
+#endif
+
+static struct request *
+sio_expired_request(struct sio_data *sd, int sync, int data_dir)
+{
+ struct list_head *list = &sd->fifo_list[sync][data_dir];
+ struct request *rq;
+
+ if (list_empty(list))
+ return NULL;
+
+ /* Retrieve request */
+ rq = rq_entry_fifo(list->next);
+
+ /* Request has expired */
+ if (time_after(jiffies, rq_fifo_time(rq)))
+ return rq;
+
+ return NULL;
+}
+
+static struct request *
+sio_choose_expired_request(struct sio_data *sd)
+{
+ struct request *rq;
+
+ /*
+ * Check expired requests.
+ * Asynchronous requests have priority over synchronous.
+ * Write requests have priority over read.
+ */
+ rq = sio_expired_request(sd, ASYNC, WRITE);
+ if (rq)
+ return rq;
+ rq = sio_expired_request(sd, ASYNC, READ);
+ if (rq)
+ return rq;
+
+ rq = sio_expired_request(sd, SYNC, WRITE);
+ if (rq)
+ return rq;
+ rq = sio_expired_request(sd, SYNC, READ);
+ if (rq)
+ return rq;
+
+ return NULL;
+}
+
+static struct request *
+sio_choose_request(struct sio_data *sd, int data_dir)
+{
+ struct list_head *sync = sd->fifo_list[SYNC];
+ struct list_head *async = sd->fifo_list[ASYNC];
+
+ /*
+ * Retrieve request from available fifo list.
+ * Synchronous requests have priority over asynchronous.
+ * Read requests have priority over write.
+ */
+ if (!list_empty(&sync[data_dir]))
+ return rq_entry_fifo(sync[data_dir].next);
+ if (!list_empty(&async[data_dir]))
+ return rq_entry_fifo(async[data_dir].next);
+
+ if (!list_empty(&sync[!data_dir]))
+ return rq_entry_fifo(sync[!data_dir].next);
+ if (!list_empty(&async[!data_dir]))
+ return rq_entry_fifo(async[!data_dir].next);
+
+ return NULL;
+}
+
+static inline void
+sio_dispatch_request(struct sio_data *sd, struct request *rq)
+{
+ /*
+ * Remove the request from the fifo list
+ * and dispatch it.
+ */
+ rq_fifo_clear(rq);
+ elv_dispatch_add_tail(rq->q, rq);
+
+ sd->batched++;
+
+ if (rq_data_dir(rq))
+ sd->starved = 0;
+ else
+ sd->starved++;
+}
+
+static int
+sio_dispatch_requests(struct request_queue *q, int force)
+{
+ struct sio_data *sd = q->elevator->elevator_data;
+ struct request *rq = NULL;
+ int data_dir = READ;
+
+ /*
+ * Retrieve any expired request after a batch of
+ * sequential requests.
+ */
+ if (sd->batched > sd->fifo_batch) {
+ sd->batched = 0;
+ rq = sio_choose_expired_request(sd);
+ }
+
+ /* Retrieve request */
+ if (!rq) {
+ if (sd->starved > sd->writes_starved)
+ data_dir = WRITE;
+
+ rq = sio_choose_request(sd, data_dir);
+ if (!rq)
+ return 0;
+ }
+
+ /* Dispatch request */
+ sio_dispatch_request(sd, rq);
+
+ return 1;
+}
+
+static struct request *
+sio_former_request(struct request_queue *q, struct request *rq)
+{
+ struct sio_data *sd = q->elevator->elevator_data;
+ const int sync = rq_is_sync(rq);
+ const int data_dir = rq_data_dir(rq);
+
+ if (rq->queuelist.prev == &sd->fifo_list[sync][data_dir])
+ return NULL;
+
+ /* Return former request */
+ return list_entry(rq->queuelist.prev, struct request, queuelist);
+}
+
+static struct request *
+sio_latter_request(struct request_queue *q, struct request *rq)
+{
+ struct sio_data *sd = q->elevator->elevator_data;
+ const int sync = rq_is_sync(rq);
+ const int data_dir = rq_data_dir(rq);
+
+ if (rq->queuelist.next == &sd->fifo_list[sync][data_dir])
+ return NULL;
+
+ /* Return latter request */
+ return list_entry(rq->queuelist.next, struct request, queuelist);
+}
+
+static void *
+sio_init_queue(struct request_queue *q)
+{
+ struct sio_data *sd;
+
+ /* Allocate structure */
+ sd = kmalloc_node(sizeof(*sd), GFP_KERNEL, q->node);
+ if (!sd)
+ return NULL;
+
+ /* Initialize fifo lists */
+ INIT_LIST_HEAD(&sd->fifo_list[SYNC][READ]);
+ INIT_LIST_HEAD(&sd->fifo_list[SYNC][WRITE]);
+ INIT_LIST_HEAD(&sd->fifo_list[ASYNC][READ]);
+ INIT_LIST_HEAD(&sd->fifo_list[ASYNC][WRITE]);
+
+ /* Initialize data */
+ sd->batched = 0;
+ sd->fifo_expire[SYNC][READ] = sync_read_expire;
+ sd->fifo_expire[SYNC][WRITE] = sync_write_expire;
+ sd->fifo_expire[ASYNC][READ] = async_read_expire;
+ sd->fifo_expire[ASYNC][WRITE] = async_write_expire;
+ sd->fifo_batch = fifo_batch;
+
+ return sd;
+}
+
+static void
+sio_exit_queue(struct elevator_queue *e)
+{
+ struct sio_data *sd = e->elevator_data;
+
+ BUG_ON(!list_empty(&sd->fifo_list[SYNC][READ]));
+ BUG_ON(!list_empty(&sd->fifo_list[SYNC][WRITE]));
+ BUG_ON(!list_empty(&sd->fifo_list[ASYNC][READ]));
+ BUG_ON(!list_empty(&sd->fifo_list[ASYNC][WRITE]));
+
+ /* Free structure */
+ kfree(sd);
+}
+
+/*
+ * sysfs code
+ */
+
+static ssize_t
+sio_var_show(int var, char *page)
+{
+ return sprintf(page, "%d\n", var);
+}
+
+static ssize_t
+sio_var_store(int *var, const char *page, size_t count)
+{
+ char *p = (char *) page;
+
+ *var = simple_strtol(p, &p, 10);
+ return count;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
+static ssize_t __FUNC(struct elevator_queue *e, char *page) \
+{ \
+ struct sio_data *sd = e->elevator_data; \
+ int __data = __VAR; \
+ if (__CONV) \
+ __data = jiffies_to_msecs(__data); \
+ return sio_var_show(__data, (page)); \
+}
+SHOW_FUNCTION(sio_sync_read_expire_show, sd->fifo_expire[SYNC][READ], 1);
+SHOW_FUNCTION(sio_sync_write_expire_show, sd->fifo_expire[SYNC][WRITE], 1);
+SHOW_FUNCTION(sio_async_read_expire_show, sd->fifo_expire[ASYNC][READ], 1);
+SHOW_FUNCTION(sio_async_write_expire_show, sd->fifo_expire[ASYNC][WRITE], 1);
+SHOW_FUNCTION(sio_fifo_batch_show, sd->fifo_batch, 0);
+SHOW_FUNCTION(sio_writes_starved_show, sd->writes_starved, 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 sio_data *sd = e->elevator_data; \
+ int __data; \
+ int ret = sio_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(sio_sync_read_expire_store, &sd->fifo_expire[SYNC][READ], 0, INT_MAX, 1);
+STORE_FUNCTION(sio_sync_write_expire_store, &sd->fifo_expire[SYNC][WRITE], 0, INT_MAX, 1);
+STORE_FUNCTION(sio_async_read_expire_store, &sd->fifo_expire[ASYNC][READ], 0, INT_MAX, 1);
+STORE_FUNCTION(sio_async_write_expire_store, &sd->fifo_expire[ASYNC][WRITE], 0, INT_MAX, 1);
+STORE_FUNCTION(sio_fifo_batch_store, &sd->fifo_batch, 0, INT_MAX, 0);
+STORE_FUNCTION(sio_writes_starved_store, &sd->writes_starved, 0, INT_MAX, 0);
+#undef STORE_FUNCTION
+
+#define DD_ATTR(name) \
+ __ATTR(name, S_IRUGO|S_IWUSR, sio_##name##_show, \
+ sio_##name##_store)
+
+static struct elv_fs_entry sio_attrs[] = {
+ DD_ATTR(sync_read_expire),
+ DD_ATTR(sync_write_expire),
+ DD_ATTR(async_read_expire),
+ DD_ATTR(async_write_expire),
+ DD_ATTR(fifo_batch),
+ DD_ATTR(writes_starved),
+ __ATTR_NULL
+};
+
+static struct elevator_type iosched_sio = {
+ .ops = {
+ .elevator_merge_req_fn = sio_merged_requests,
+ .elevator_dispatch_fn = sio_dispatch_requests,
+ .elevator_add_req_fn = sio_add_request,
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,38)
+ .elevator_queue_empty_fn = sio_queue_empty,
+#endif
+ .elevator_former_req_fn = sio_former_request,
+ .elevator_latter_req_fn = sio_latter_request,
+ .elevator_init_fn = sio_init_queue,
+ .elevator_exit_fn = sio_exit_queue,
+ },
+
+ .elevator_attrs = sio_attrs,
+ .elevator_name = "sio",
+ .elevator_owner = THIS_MODULE,
+};
+
+static int __init sio_init(void)
+{
+ /* Register elevator */
+ elv_register(&iosched_sio);
+
+ return 0;
+}
+
+static void __exit sio_exit(void)
+{
+ /* Unregister elevator */
+ elv_unregister(&iosched_sio);
+}
+
+module_init(sio_init);
+module_exit(sio_exit);
+
+MODULE_AUTHOR("Miguel Boton");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Simple IO scheduler");
+MODULE_VERSION("0.2");
projects / ziggy471-sgs3-jb.git / commitdiff