anticipatory I/O scheduler
drivers/block/Makefile | 3
drivers/block/as-iosched.c | 1751 +++++++++++++++++++++++++++++++++++++++++++++
drivers/block/ll_rw_blk.c | 19
include/linux/elevator.h | 5
include/linux/sched.h | 4
kernel/exit.c | 2
kernel/fork.c | 1
7 files changed, 1783 insertions(+), 2 deletions(-)
diff -puN /dev/null drivers/block/as-iosched.c
--- /dev/null 2002-08-30 16:31:37.000000000 -0700
+++ 25-akpm/drivers/block/as-iosched.c 2003-04-01 02:33:29.000000000 -0800
@@ -0,0 +1,1751 @@
+/*
+ * linux/drivers/block/as-iosched.c
+ *
+ * Anticipatory & deadline i/o scheduler.
+ *
+ * Copyright (C) 2002 Jens Axboe <axboe@suse.de>
+ * Nick Piggin <piggin@cyberone.com.au>
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/blk.h>
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/compiler.h>
+#include <linux/hash.h>
+#include <linux/rbtree.h>
+#include <linux/interrupt.h>
+
+struct ant_stats {
+ int reads; /* total read requests */
+ int writes; /* total write requests */
+ int anticipate_starts;
+ int expired_read_batches;
+ int expired_write_batches;
+ int timeouts;
+ int kblockd_calls;
+ int anticipate_hits;
+ int expired_fifo_reads;
+ int expired_fifo_writes;
+ int close_requests;
+ int matching_ids;
+ int broken_by_write;
+ int exitted_tasks;
+ int queued_request;
+ int big_thinktime;
+
+ int ant_delay_hist[100]; /* milliseconds */
+
+ /*
+ * This is a logarithmic (base 2) histogram
+ */
+ int lba_forward_offsets[BITS_PER_LONG];
+ int lba_backward_offsets[BITS_PER_LONG];
+} ant_stats;
+
+/*
+ * See Documentation/as-iosched.txt
+ */
+
+/*
+ * max time before a read is submitted.
+ */
+static unsigned long read_expire = HZ / 20;
+
+/*
+ * ditto for writes, these limits are not hard, even
+ * if the disk is capable of satisfying them.
+ */
+static unsigned long write_expire = HZ / 2;
+
+/*
+ * read_batch_expire describes how long we will allow a stream of reads to
+ * persist before looking to see whether it is time to switch over to writes.
+ */
+static unsigned long read_batch_expire = HZ / 5;
+
+/*
+ * write_batch_expire describes how long we will allow a stream of writes to
+ * persist before looking to see whether it is time to switch over to reads.
+ */
+static unsigned long write_batch_expire = HZ / 20;
+
+/*
+ * max time we may wait to anticipate a read
+ */
+static unsigned long antic_expire = HZ / 100;
+
+/*
+ * This is the per-process anticipatory I/O scheduler state. It is refcounted
+ * and kmalloc'ed.
+ *
+ * There is no locking protecting the contents of this structure! Pointers
+ * to a single as_io_context may appear in multiple queues at once.
+ */
+
+/* Keep track of up to 30ms thinktimes */
+#define MAX_THINKTIME (HZ/33UL)
+
+struct as_io_context {
+ atomic_t refcount;
+ pid_t pid;
+ unsigned long state;
+ atomic_t nr_queued; /* queued reads & sync writes */
+ atomic_t nr_dispatched; /* number of requests gone to the drivers */
+
+ /* IO History tracking */
+ unsigned long last_end_request;
+ unsigned long thinktime[MAX_THINKTIME];
+ unsigned long mean_thinktime;
+};
+
+/* Bits in as_io_context.state */
+enum as_io_states {
+ AS_TASK_RUNNING=0, /* Process has not exitted */
+ AS_TASK_IORUNNING, /* Process has completed some IO */
+};
+
+struct as_data {
+ /*
+ * run time data
+ */
+
+ struct request_queue *q; /* the "owner" queue */
+
+ /*
+ * requests (as_rq s) are present on both sort_list and fifo_list
+ */
+ struct rb_root sort_list[2];
+ struct list_head fifo_list[2];
+
+ struct as_rq *next_arq[2]; /* next in sort order */
+ sector_t last_sector[2]; /* last READ and WRITE sectors */
+ struct list_head *dispatch; /* driver dispatch queue */
+ struct list_head *hash; /* request hash */
+ unsigned long hash_valid_count; /* barrier hash count */
+ unsigned long current_batch_expires;
+ unsigned long last_check_fifo[2];
+ int batch_data_dir; /* current/last batch READ or WRITE */
+
+ int antic_status;
+ unsigned long antic_start; /* jiffies: when it started */
+ struct timer_list antic_timer; /* anticipatory scheduling timer */
+ struct work_struct antic_work; /* Deferred unplugging */
+ struct as_io_context *as_io_context;/* Identify the expected process */
+ int aic_finished; /* IO associated with as_io_context finished */
+
+ /*
+ * settings that change how the i/o scheduler behaves
+ */
+ unsigned long fifo_expire[2];
+ unsigned long batch_expire[2];
+ unsigned long front_merges;
+ unsigned long antic_expire;
+};
+
+#define list_entry_fifo(ptr) list_entry((ptr), struct as_rq, fifo)
+
+enum anticipation_states {
+ ANTIC_OFF=0, /* Not anticipating (normal operation) */
+ ANTIC_WAIT_REQ, /* The last read has not yet completed */
+ ANTIC_WAIT_NEXT, /* Currently anticipating a request vs
+ last read (which has completed) */
+ ANTIC_FINISHED, /* Anticipating but have found a candidate
+ or timed out */
+};
+
+/*
+ * per-request data.
+ */
+enum arq_state {
+ AS_RQ_NEW=0, /* New - not referenced and not on any lists */
+ AS_RQ_QUEUED, /* In the request queue. It belongs to the
+ scheduler */
+ AS_RQ_DISPATCHED, /* On the dispatch list. It belongs to the
+ driver now */
+};
+
+struct as_rq {
+ /*
+ * rbtree index, key is the starting offset
+ */
+ struct rb_node rb_node;
+ sector_t rb_key;
+
+ struct request *request;
+
+ struct as_io_context *as_io_context; /* The submitting task */
+
+ /*
+ * request hash, key is the ending offset (for back merge lookup)
+ */
+ struct list_head hash;
+ unsigned long hash_valid_count;
+
+ /*
+ * expire fifo
+ */
+ struct list_head fifo;
+ unsigned long expires;
+
+ enum arq_state state; /* debug only */
+};
+
+#define RQ_DATA(rq) ((struct as_rq *) (rq)->elevator_private)
+
+static kmem_cache_t *arq_pool;
+
+/*
+ * IO Context helper functions
+ */
+/* Debug */
+static atomic_t nr_as_io_requests = ATOMIC_INIT(0);
+
+static void put_as_io_context(struct as_io_context **paic)
+{
+ struct as_io_context *aic = *paic;
+
+ if (aic == NULL)
+ return;
+
+ BUG_ON(atomic_read(&aic->refcount) == 0);
+ *paic = NULL;
+ if (atomic_dec_and_test(&aic->refcount)) {
+ atomic_dec(&nr_as_io_requests);
+ kfree(aic);
+ }
+}
+
+/* Called by the exitting task */
+void exit_as_io_context(void)
+{
+ unsigned long flags;
+ struct as_io_context *aic;
+
+ local_irq_save(flags);
+ aic = current->as_io_context;
+ if (aic) {
+ clear_bit(AS_TASK_RUNNING, &aic->state);
+ put_as_io_context(&aic);
+ current->as_io_context = NULL;
+ }
+ local_irq_restore(flags);
+}
+
+/*
+ * If the current task has no IO context then create one and initialise it.
+ * If it does have a context, take a ref on it.
+ *
+ * This is always called in the context of the task which submitted the I/O.
+ * But weird things happen, so we disable local interrupts to ensure exclusive
+ * access to *current.
+ */
+static struct as_io_context *get_as_io_context(void)
+{
+ struct task_struct *tsk = current;
+ unsigned long flags;
+ struct as_io_context *ret;
+
+ local_irq_save(flags);
+ ret = tsk->as_io_context;
+ if (ret == NULL) {
+ ret = kmalloc(sizeof(*ret), GFP_ATOMIC);
+ if (ret) {
+ atomic_inc(&nr_as_io_requests);
+ atomic_set(&ret->refcount, 1);
+ ret->pid = tsk->pid;
+ ret->state = 1 << AS_TASK_RUNNING;
+ atomic_set(&ret->nr_queued, 0);
+ atomic_set(&ret->nr_dispatched, 0);
+ memset(ret->thinktime, 0, sizeof(ret->thinktime));
+ ret->mean_thinktime = 0;
+ tsk->as_io_context = ret;
+ }
+ }
+ local_irq_restore(flags);
+ atomic_inc(&ret->refcount);
+ return ret;
+}
+
+static void
+copy_as_io_context(struct as_io_context **pdst, struct as_io_context **psrc)
+{
+ struct as_io_context *src = *psrc;
+
+ if (src) {
+ BUG_ON(atomic_read(&src->refcount) == 0);
+ atomic_inc(&src->refcount);
+ put_as_io_context(pdst);
+ *pdst = src;
+ }
+}
+
+static void
+swap_as_io_context(struct as_io_context **aic1, struct as_io_context **aic2)
+{
+ struct as_io_context *temp;
+ temp = *aic1;
+ *aic1 = *aic2;
+ *aic2 = temp;
+}
+
+/*
+ * the back merge hash support functions
+ */
+static const int as_hash_shift = 10;
+#define AS_HASH_BLOCK(sec) ((sec) >> 3)
+#define AS_HASH_FN(sec) (hash_long(AS_HASH_BLOCK((sec)), as_hash_shift))
+#define AS_HASH_ENTRIES (1 << as_hash_shift)
+#define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors)
+#define list_entry_hash(ptr) list_entry((ptr), struct as_rq, hash)
+#define ON_HASH(arq) (arq)->hash_valid_count
+
+#define AS_INVALIDATE_HASH(ad) \
+ do { \
+ if (!++(ad)->hash_valid_count) \
+ (ad)->hash_valid_count = 1; \
+ } while (0)
+
+static inline void __as_del_arq_hash(struct as_rq *arq)
+{
+ arq->hash_valid_count = 0;
+ list_del_init(&arq->hash);
+}
+
+static inline void as_del_arq_hash(struct as_rq *arq)
+{
+ if (ON_HASH(arq))
+ __as_del_arq_hash(arq);
+}
+
+static void as_add_arq_hash(struct as_data *ad, struct as_rq *arq)
+{
+ struct request *rq = arq->request;
+
+ BUG_ON(ON_HASH(arq));
+
+ arq->hash_valid_count = ad->hash_valid_count;
+ list_add(&arq->hash, &ad->hash[AS_HASH_FN(rq_hash_key(rq))]);
+}
+
+static struct request *as_find_arq_hash(struct as_data *ad, sector_t offset)
+{
+ struct list_head *hash_list = &ad->hash[AS_HASH_FN(offset)];
+ struct list_head *entry, *next = hash_list->next;
+
+ while ((entry = next) != hash_list) {
+ struct as_rq *arq = list_entry_hash(entry);
+ struct request *__rq = arq->request;
+
+ next = entry->next;
+
+ BUG_ON(!ON_HASH(arq));
+
+ if (!rq_mergeable(__rq)
+ || arq->hash_valid_count != ad->hash_valid_count) {
+ __as_del_arq_hash(arq);
+ continue;
+ }
+
+ if (rq_hash_key(__rq) == offset)
+ return __rq;
+ }
+
+ return NULL;
+}
+
+/*
+ * rb tree support functions
+ */
+#define RB_NONE (2)
+#define RB_EMPTY(root) ((root)->rb_node == NULL)
+#define ON_RB(node) ((node)->rb_color != RB_NONE)
+#define RB_CLEAR(node) ((node)->rb_color = RB_NONE)
+#define rb_entry_arq(node) rb_entry((node), struct as_rq, rb_node)
+#define ARQ_RB_ROOT(ad, arq) (&(ad)->sort_list[rq_data_dir((arq)->request)])
+#define rq_rb_key(rq) (rq)->sector
+
+/*
+ * as_find_first_arq finds the first (lowest sector numbered) request
+ * for the specified data_dir. Used to sweep back to the start of the disk
+ * (1-way elevator) after we process the last (highest sector) request.
+ */
+static struct as_rq *as_find_first_arq(struct as_data *ad, int data_dir)
+{
+ struct rb_node *n = ad->sort_list[data_dir].rb_node;
+
+ if (n == NULL)
+ return NULL;
+
+ for (;;) {
+ if (n->rb_left == NULL)
+ return rb_entry_arq(n);
+
+ n = n->rb_left;
+ }
+}
+
+static struct as_rq *__as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
+{
+ struct rb_node **p = &ARQ_RB_ROOT(ad, arq)->rb_node;
+ struct rb_node *parent = NULL;
+ struct as_rq *__arq;
+
+ while (*p) {
+ parent = *p;
+ __arq = rb_entry_arq(parent);
+
+ if (arq->rb_key < __arq->rb_key)
+ p = &(*p)->rb_left;
+ else if (arq->rb_key > __arq->rb_key)
+ p = &(*p)->rb_right;
+ else
+ return __arq;
+ }
+
+ rb_link_node(&arq->rb_node, parent, p);
+ return 0;
+}
+
+static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq);
+/*
+ * Aad the request to the rb tree if it is unique. If there is an alias (an
+ * existing request against the same sector), which can happen when using
+ * direct IO, then move the alias to the dispatch list and then add the
+ * request.
+ */
+static void as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
+{
+ struct as_rq *alias;
+ struct request *rq = arq->request;
+
+ arq->rb_key = rq_rb_key(rq);
+
+ /* This can be caused by direct IO */
+ while ((alias = __as_add_arq_rb(ad, arq)))
+ as_move_to_dispatch(ad, alias);
+
+ rb_insert_color(&arq->rb_node, ARQ_RB_ROOT(ad, arq));
+}
+
+static inline void as_del_arq_rb(struct as_data *ad, struct as_rq *arq)
+{
+ if (ON_RB(&arq->rb_node)) {
+ rb_erase(&arq->rb_node, ARQ_RB_ROOT(ad, arq));
+ RB_CLEAR(&arq->rb_node);
+ }
+}
+
+static struct request *
+as_find_arq_rb(struct as_data *ad, sector_t sector, int data_dir)
+{
+ struct rb_node *n = ad->sort_list[data_dir].rb_node;
+ struct as_rq *arq;
+
+ while (n) {
+ arq = rb_entry_arq(n);
+
+ if (sector < arq->rb_key)
+ n = n->rb_left;
+ else if (sector > arq->rb_key)
+ n = n->rb_right;
+ else
+ return arq->request;
+ }
+
+ return NULL;
+}
+
+/*
+ * IO Scheduler proper
+ */
+
+#define MAXBACK (512 * 1024) /* Maximum distance a process can seek backward
+ from a previous request it has made. No
+ seeking backward between processes allowed */
+
+/*
+ * as_choose_req selects the preferred one of two requests of the same data_dir
+ * ignoring time - eg. timeouts, which is the job of as_dispatch_request
+ */
+static struct as_rq *
+as_choose_req(struct as_data *ad, struct as_rq *arq1, struct as_rq *arq2)
+{
+ int data_dir;
+ sector_t last, s1, s2, d1, d2;
+ int r1_wrap=0, r2_wrap=0; /* requests are behind the disk head */
+ const sector_t maxback = MAXBACK;
+
+ if (arq1 == NULL || arq1 == arq2)
+ return arq2;
+ if (arq2 == NULL)
+ return arq1;
+
+ data_dir = rq_data_dir(arq1->request);
+
+ last = ad->last_sector[data_dir];
+ s1 = arq1->request->sector;
+ s2 = arq2->request->sector;
+
+ BUG_ON(data_dir != rq_data_dir(arq2->request));
+
+ /*
+ * Strict one way elevator _except_ in the case where we allow
+ * short backward seeks which are biased as twice the cost of a
+ * similar forward seek. Only for reads and only between reads
+ * from the same process!
+ */
+ if (s1 >= last)
+ d1 = s1 - last;
+ else if (data_dir == READ
+ && ad->as_io_context == arq1->as_io_context
+ && s1+maxback >= last)
+ d1 = (last - s1)*2;
+ else {
+ r1_wrap = 1;
+ d1 = 0; /* shut up, gcc */
+ }
+
+ if (s2 >= last)
+ d2 = s2 - last;
+ else if (data_dir == READ
+ && ad->as_io_context == arq2->as_io_context
+ && s2+maxback >= last)
+ d2 = (last - s2)*2;
+ else {
+ r2_wrap = 1;
+ d2 = 0;
+ }
+
+ /* Found required data */
+ if (!r1_wrap && r2_wrap)
+ return arq1;
+ else if (!r2_wrap && r1_wrap)
+ return arq2;
+ else if (r1_wrap && r2_wrap) {
+ /* both behind the head */
+ if (s1 <= s2)
+ return arq1;
+ else
+ return arq2;
+ }
+
+ /* Both requests in front of the head */
+ if (d1 < d2)
+ return arq1;
+ else if (d2 < d1)
+ return arq2;
+ else {
+ if (s1 >= s2)
+ return arq1;
+ else
+ return arq2;
+ }
+}
+
+/*
+ * as_find_next_arq finds the next request after @prev in elevator order.
+ * this with as_choose_arq form the basis for how the scheduler chooses
+ * what request to process next. Anticipation works on top of this.
+ */
+static struct as_rq *as_find_next_arq(struct as_data *ad, struct as_rq *last)
+{
+ const int data_dir = rq_data_dir(last->request);
+ struct as_rq *ret;
+ struct rb_node *rbnext = rb_next(&last->rb_node);
+ struct rb_node *rbprev = rb_prev(&last->rb_node);
+ struct as_rq *arq_next, *arq_prev;
+
+ BUG_ON(!ON_RB(&last->rb_node));
+
+ if (rbprev)
+ arq_prev = rb_entry_arq(rbprev);
+ else
+ arq_prev = NULL;
+
+ if (rbnext)
+ arq_next = rb_entry_arq(rbnext);
+ else {
+ arq_next = as_find_first_arq(ad, data_dir);
+ if (arq_next == last)
+ arq_next = NULL;
+ }
+
+ ret = as_choose_req(ad, arq_next, arq_prev);
+
+ return ret;
+}
+
+/*
+ * anticipatory scheduling functions follow
+ */
+
+/*
+ * as_antic_expired tells us when we have anticipated too long.
+ * The funny "absolute difference" math on the elapsed time is to handle
+ * jiffy wraps, and disks which have been idle for 0x80000000 jiffies.
+ */
+static int as_antic_expired(struct as_data *ad)
+{
+ long delta_jif;
+
+ delta_jif = jiffies - ad->antic_start;
+ if (unlikely(delta_jif < 0))
+ delta_jif = -delta_jif;
+ if (delta_jif < ad->antic_expire)
+ return 0;
+
+ return 1;
+}
+
+/*
+ * as_antic_waitnext starts anticipating that a nice request will soon be
+ * submitted. See also as_antic_waitreq
+ */
+static void as_antic_waitnext(struct as_data *ad)
+{
+ unsigned long timeout;
+
+ BUG_ON(ad->antic_status != ANTIC_OFF
+ && ad->antic_status != ANTIC_WAIT_REQ);
+
+ timeout = ad->antic_start + ad->antic_expire;
+#if 0 /* TODO unif me. This should be fixed. */
+ timeout = min(timeout, ad->current_batch_expires);
+#endif
+ mod_timer(&ad->antic_timer, timeout);
+
+ ad->antic_status = ANTIC_WAIT_NEXT;
+}
+
+/*
+ * as_antic_waitreq starts anticipating. We don't start timing the anticipation
+ * until the request that we're anticipating on has finished. This means we
+ * are timing from when the candidate process wakes up hopefully.
+ */
+static void as_antic_waitreq(struct as_data *ad)
+{
+ BUG_ON(ad->antic_status == ANTIC_FINISHED);
+ if (ad->antic_status == ANTIC_OFF) {
+ ant_stats.anticipate_starts++;
+
+ if (!ad->as_io_context || ad->aic_finished)
+ as_antic_waitnext(ad);
+ else
+ ad->antic_status = ANTIC_WAIT_REQ;
+ }
+}
+
+/*
+ * This is called directly by the functions in this file to stop anticipation.
+ * We kill the timer and schedule a call to the request_fn asap.
+ */
+static void as_antic_stop(struct as_data *ad)
+{
+ int status = ad->antic_status;
+
+ if (status == ANTIC_WAIT_REQ || status == ANTIC_WAIT_NEXT) {
+ if (status == ANTIC_WAIT_NEXT)
+ del_timer(&ad->antic_timer);
+ ad->antic_status = ANTIC_FINISHED;
+ /* see as_work_handler */
+ kblockd_schedule_work(&ad->antic_work);
+ }
+}
+
+/*
+ * as_antic_timeout is the timer function set by as_antic_waitnext.
+ */
+static void as_antic_timeout(unsigned long data)
+{
+ struct request_queue *q = (struct request_queue *)data;
+ struct as_data *ad = q->elevator.elevator_data;
+ int status = ad->antic_status;
+
+ ant_stats.timeouts++;
+ if (status == ANTIC_WAIT_REQ || status == ANTIC_WAIT_NEXT) {
+ ad->antic_status = ANTIC_FINISHED;
+ kblockd_schedule_work(&ad->antic_work);
+ }
+}
+
+/*
+ * as_close_req decides if one request is considered "close" to the
+ * previous one issued.
+ */
+static int as_close_req(struct as_data *ad, struct as_rq *arq)
+{
+ unsigned long delay; /* milliseconds */
+ sector_t last = ad->last_sector[ad->batch_data_dir];
+ sector_t next = arq->request->sector;
+ sector_t delta; /* acceptable close offset (in sectors) */
+
+ if (ad->antic_status == ANTIC_OFF || ad->antic_status == ANTIC_WAIT_REQ)
+ delay = 0;
+ else
+ delay = ((jiffies - ad->antic_start) * 1000) / HZ;
+
+ if (delay <= 1)
+ delta = 32;
+ else if (delay <= 20 && delay <= ad->antic_expire / 2)
+ delta = 32 << (delay-1);
+ else
+ return 1;
+
+ return (last <= next) && (next <= last + delta);
+}
+
+/*
+ * as_can_break_anticipation returns true if we have been anticipating this
+ * request.
+ *
+ * It also returns true if the process against which we are anticipating
+ * submits a write - that's presumably an fsync, O_SYNC write, etc. We want to
+ * dispatch it ASAP, because we know that application will not be submitting
+ * any new reads.
+ *
+ * If the task which has submitted the request has exitted, break anticipation.
+ *
+ * If this task has queued some other IO, do not enter enticipation.
+ */
+static int as_can_break_anticipation(struct as_data *ad, struct as_rq *arq)
+{
+ struct as_io_context *aic;
+
+ if (ad->antic_status == ANTIC_WAIT_NEXT && as_antic_expired(ad)) {
+ /*
+ * In this situation status should really be FINISHED,
+ * however the timer hasn't had the chance to run yet.
+ */
+ return 1;
+ }
+
+ if (rq_data_dir(arq->request) == READ && as_close_req(ad, arq)) {
+ ant_stats.close_requests++;
+ return 1;
+ }
+
+ if (ad->as_io_context == arq->as_io_context) {
+ ant_stats.matching_ids++;
+ if (rq_data_dir(arq->request) == WRITE)
+ ant_stats.broken_by_write++;
+ return 1;
+ }
+
+ aic = ad->as_io_context;
+ if (aic && !test_bit(AS_TASK_RUNNING, &aic->state)) {
+ ant_stats.exitted_tasks++;
+ return 1;
+ }
+
+ if (aic && atomic_read(&aic->nr_queued) > 0) {
+ ant_stats.queued_request++;
+ return 1;
+ }
+
+ if (aic && aic->mean_thinktime > max(HZ/200, 1)) {
+ ant_stats.big_thinktime++;
+ return 1;
+ }
+
+ return 0;
+}
+
+/*
+ * as_can_anticipate indicates weather we should either run arq
+ * or keep anticipating a better request.
+ */
+static int as_can_anticipate(struct as_data *ad, struct as_rq *arq)
+{
+ if (!ad->as_io_context)
+ /*
+ * Last request submitted was a write
+ */
+ return 0;
+
+ if (ad->antic_status == ANTIC_FINISHED)
+ /*
+ * Don't restart if we have just finished. Run the next request
+ */
+ return 0;
+
+ if (arq && as_can_break_anticipation(ad, arq))
+ /*
+ * This request is a good candidate. Don't keep anticipating,
+ * run it.
+ */
+ return 0;
+
+ /*
+ * OK from here, we haven't finished, and don't have a decent request!
+ * Status is either ANTIC_OFF so start waiting,
+ * ANTIC_WAIT_REQ so continue waiting for request to finish
+ * or ANTIC_WAIT_NEXT so continue waiting for an acceptable request.
+ *
+ */
+
+ return 1;
+}
+
+/*
+ * as_update_iohist keeps a decaying histogram of IO thinktimes, and
+ * updates @aic->mean_thinktime based on that. It is called when a new
+ * request is queued.
+ */
+static void as_update_iohist(struct as_io_context *aic)
+{
+ unsigned i;
+ unsigned long thinktime;
+ unsigned long total = 0;
+ unsigned long num = 0;
+
+ if (aic == NULL)
+ return;
+
+ if (test_bit(AS_TASK_IORUNNING, &aic->state)) {
+ thinktime = jiffies - aic->last_end_request;
+ thinktime = min(thinktime, MAX_THINKTIME-1);
+ aic->thinktime[thinktime] += 256; /* fixed point: 1.0 == 1<<8 */
+
+ for (i = 0; i < MAX_THINKTIME; i++) {
+ unsigned long tt = aic->thinktime[i];
+ total += i*tt;
+ num += tt;
+
+ aic->thinktime[i] = (tt>>1) + (tt>>2); /* 75% decay */
+ }
+ /* fixed point factor is cancelled here */
+ if (num)
+ aic->mean_thinktime = total / num;
+ }
+}
+
+/*
+ * as_update_arq must be called whenever a request (arq) is added to
+ * the sort_list. This function keeps caches up to date, and checks if the
+ * request might be one we are "anticipating"
+ */
+static void as_update_arq(struct as_data *ad, struct as_rq *arq)
+{
+ const int data_dir = rq_data_dir(arq->request);
+
+ if (data_dir == READ)
+ ant_stats.reads++;
+ else
+ ant_stats.writes++;
+
+ /* keep the next_arq cache up to date */
+ ad->next_arq[data_dir] = as_choose_req(ad, arq, ad->next_arq[data_dir]);
+
+ /*
+ * have we been anticipating this request?
+ * or does it come from the same process as the one we are anticipating
+ * for?
+ */
+ if (ad->batch_data_dir == READ && ad->antic_status != ANTIC_FINISHED
+ && as_can_break_anticipation(ad, arq)) {
+ sector_t last = ad->last_sector[data_dir];
+ sector_t this = arq->request->sector;
+ unsigned long delay;
+ long lba_offset;
+ int neg;
+ int log2;
+
+ if (ad->antic_status == ANTIC_WAIT_REQ)
+ delay = 0;
+ else
+ delay = jiffies - ad->antic_start;
+
+ if (data_dir == READ) {
+ if (delay >= ARRAY_SIZE(ant_stats.ant_delay_hist))
+ delay = ARRAY_SIZE(ant_stats.ant_delay_hist)-1;
+ ant_stats.ant_delay_hist[delay]++;
+ ant_stats.anticipate_hits++;
+
+ lba_offset = this - last;
+ neg = 0;
+ if (lba_offset < 0) {
+ lba_offset = -lba_offset;
+ neg = 1;
+ }
+ log2 = ffs(lba_offset);
+ if (neg)
+ ant_stats.lba_backward_offsets[log2]++;
+ else
+ ant_stats.lba_forward_offsets[log2]++;
+ }
+
+ as_antic_stop(ad);
+ }
+}
+
+/*
+ * as_complete_arq is to be called when a request has completed and returned
+ * something to the requesting process, be it an error or data.
+ */
+static void as_complete_arq(struct as_data *ad, struct as_rq *arq)
+{
+ if (!arq->as_io_context)
+ return;
+
+ if (rq_data_dir(arq->request) == READ) {
+ set_bit(AS_TASK_IORUNNING, &arq->as_io_context->state);
+ arq->as_io_context->last_end_request = jiffies;
+ }
+
+ if (ad->as_io_context == arq->as_io_context) {
+ ad->antic_start = jiffies;
+ ad->aic_finished = 1;
+ if (ad->antic_status == ANTIC_WAIT_REQ) {
+ /*
+ * We were waiting on this request, now anticipate
+ * the next one
+ */
+ as_antic_waitnext(ad);
+ }
+ }
+}
+
+/*
+ * as_remove_queued_request removes a request from the pre dispatch queue
+ * without updating refcounts. It is expected the caller will drop the
+ * reference unless it replaces the request at somepart of the elevator
+ * (ie. the dispatch queue)
+ */
+static void as_remove_queued_request(request_queue_t *q, struct request *rq)
+{
+ struct as_rq *arq = RQ_DATA(rq);
+
+ if (!arq)
+ BUG();
+ else {
+ const int data_dir = rq_data_dir(arq->request);
+ struct as_data *ad = q->elevator.elevator_data;
+
+ WARN_ON(arq->state != AS_RQ_QUEUED);
+
+ if (arq->as_io_context) {
+ BUG_ON(!atomic_read(&arq->as_io_context->nr_queued));
+ atomic_dec(&arq->as_io_context->nr_queued);
+ }
+
+ /*
+ * Update the "next_arq" cache if we are about to remove its
+ * entry
+ */
+ if (ad->next_arq[data_dir] == arq)
+ ad->next_arq[data_dir] = as_find_next_arq(ad, arq);
+
+ list_del_init(&arq->fifo);
+ as_del_arq_hash(arq);
+ as_del_arq_rb(ad, arq);
+
+ if (q->last_merge == &rq->queuelist)
+ q->last_merge = NULL;
+
+ list_del_init(&rq->queuelist);
+ }
+
+}
+
+/*
+ * as_remove_dispatched_request is called to remove a request which has gone
+ * to the dispatch list.
+ */
+static void as_remove_dispatched_request(request_queue_t *q, struct request *rq)
+{
+ struct as_rq *arq = RQ_DATA(rq);
+
+ if (q->last_merge == &rq->queuelist)
+ q->last_merge = NULL;
+
+ list_del_init(&rq->queuelist);
+
+ if (arq) {
+ struct as_io_context *aic;
+
+ WARN_ON(arq->state != AS_RQ_DISPATCHED);
+ WARN_ON(ON_RB(&arq->rb_node));
+ aic = arq->as_io_context;
+ if (aic) {
+ WARN_ON(!atomic_read(&aic->nr_dispatched));
+ atomic_dec(&arq->as_io_context->nr_dispatched);
+ }
+ }
+}
+/*
+ * as_remove_request is called when a driver has finished with a request.
+ * This should be only called for dispatched requests, but for some reason
+ * a POWER4 box running hwscan it does not.
+ */
+static void as_remove_request(request_queue_t *q, struct request *rq)
+{
+ struct as_data *ad = q->elevator.elevator_data;
+ struct as_rq *arq = RQ_DATA(rq);
+
+ if (unlikely(!blk_fs_request(rq)))
+ return;
+
+ if (arq) {
+ if (ON_RB(&arq->rb_node))
+ as_remove_queued_request(q, rq);
+ else
+ as_remove_dispatched_request(q, rq);
+
+ as_complete_arq(ad, arq);
+ arq->state = AS_RQ_NEW;
+ put_as_io_context(&arq->as_io_context);
+ }
+}
+
+/*
+ * as_fifo_expired returns 0 if there are no expired reads on the fifo,
+ * 1 otherwise. It is ratelimited so that we only perform the check once per
+ * `fifo_expire' interval. Otherwise a large number of expired requests
+ * would create a hopeless seekstorm.
+ *
+ * See as_antic_expired comment.
+ */
+static int as_fifo_expired(struct as_data *ad, int adir)
+{
+ struct as_rq *arq;
+ long delta_jif;
+
+ delta_jif = jiffies - ad->last_check_fifo[adir];
+ if (unlikely(delta_jif < 0))
+ delta_jif = -delta_jif;
+ if (delta_jif < ad->fifo_expire[adir])
+ return 0;
+
+ ad->last_check_fifo[adir] = jiffies;
+
+ if (list_empty(&ad->fifo_list[adir]))
+ return 0;
+
+ arq = list_entry_fifo(ad->fifo_list[adir].next);
+
+ return time_after(jiffies, arq->expires);
+}
+
+/*
+ * as_batch_expired returns true if the current batch has expired. A batch
+ * is a set of reads or a set of writes.
+ */
+static inline int as_batch_expired(struct as_data *ad)
+{
+ return time_after(jiffies, ad->current_batch_expires);
+}
+
+/*
+ * move an entry to dispatch queue
+ */
+static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
+{
+ const int data_dir = rq_data_dir(arq->request);
+
+ BUG_ON(!ON_RB(&arq->rb_node));
+
+ as_antic_stop(ad);
+ ad->antic_status = ANTIC_OFF;
+
+ /*
+ * This has to be set in order to be correctly updated by
+ * as_find_next_arq
+ */
+ ad->last_sector[data_dir] = arq->request->sector
+ + arq->request->nr_sectors;
+
+ if (data_dir == READ) {
+ /* In case we have to anticipate after this */
+ copy_as_io_context(&ad->as_io_context, &arq->as_io_context);
+ ad->aic_finished = 0;
+ } else
+ put_as_io_context(&ad->as_io_context);
+
+ ad->next_arq[data_dir] = as_find_next_arq(ad, arq);
+
+ /*
+ * take it off the sort and fifo list, add to dispatch queue
+ */
+ as_remove_queued_request(ad->q, arq->request);
+ list_add_tail(&arq->request->queuelist, ad->dispatch);
+ if (arq->as_io_context)
+ atomic_inc(&arq->as_io_context->nr_dispatched);
+
+ WARN_ON(arq->state != AS_RQ_QUEUED);
+ arq->state = AS_RQ_DISPATCHED;
+}
+
+/*
+ * as_dispatch_request selects the best request according to
+ * read/write expire, batch expire, etc, and moves it to the dispatch
+ * queue. Returns 1 if a request was found, 0 otherwise.
+ */
+static int as_dispatch_request(struct as_data *ad)
+{
+ struct as_rq *arq;
+ const int reads = !list_empty(&ad->fifo_list[READ]);
+ const int writes = !list_empty(&ad->fifo_list[WRITE]);
+
+ if (!(reads || writes))
+ return 0;
+
+ if (as_batch_expired(ad)) {
+ if (ad->batch_data_dir == READ)
+ ant_stats.expired_read_batches++;
+ else
+ ant_stats.expired_write_batches++;
+ }
+
+ if (!(reads && writes && as_batch_expired(ad))) {
+ /*
+ * batch is still running or no reads or no writes
+ */
+ arq = ad->next_arq[ad->batch_data_dir];
+
+ if (ad->batch_data_dir == READ && ad->antic_expire) {
+ if (as_fifo_expired(ad, READ))
+ goto fifo_expired;
+
+ if (as_can_anticipate(ad, arq)) {
+ as_antic_waitreq(ad);
+ return 0;
+ }
+ }
+
+ if (arq) {
+ /* we have a "next request" */
+ if (reads && !writes)
+ ad->current_batch_expires =
+ jiffies + ad->batch_expire[READ];
+ goto dispatch_request;
+ }
+ }
+
+ /*
+ * at this point we are not running a batch. select the appropriate
+ * data direction (read / write)
+ */
+
+ if (reads) {
+ BUG_ON(RB_EMPTY(&ad->sort_list[READ]));
+
+ if (writes && ad->batch_data_dir == READ)
+ /*
+ * Last batch was a read, switch to writes
+ */
+ goto dispatch_writes;
+
+ ad->batch_data_dir = READ;
+ arq = ad->next_arq[ad->batch_data_dir];
+ ad->current_batch_expires = jiffies +
+ ad->batch_expire[ad->batch_data_dir];
+ goto dispatch_request;
+ }
+
+ /*
+ * there are either no reads or the last batch was a read
+ */
+
+ if (writes) {
+dispatch_writes:
+ BUG_ON(RB_EMPTY(&ad->sort_list[WRITE]));
+
+ ad->batch_data_dir = WRITE;
+ arq = ad->next_arq[ad->batch_data_dir];
+ ad->current_batch_expires = jiffies +
+ ad->batch_expire[ad->batch_data_dir];
+ goto dispatch_request;
+ }
+
+ BUG();
+ return 0;
+
+dispatch_request:
+ /*
+ * If a request has expired, service it.
+ */
+
+ if (as_fifo_expired(ad, ad->batch_data_dir)) {
+fifo_expired:
+ if (ad->batch_data_dir == WRITE)
+ ant_stats.expired_fifo_writes++;
+ else
+ ant_stats.expired_fifo_reads++;
+ arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next);
+ BUG_ON(arq == NULL);
+ }
+
+ /*
+ * arq is the selected appropriate request.
+ */
+ as_move_to_dispatch(ad, arq);
+
+ return 1;
+}
+
+static struct request *as_next_request(request_queue_t *q)
+{
+ struct as_data *ad = q->elevator.elevator_data;
+ struct request *rq = NULL;
+
+ /*
+ * if there are still requests on the dispatch queue, grab the first
+ */
+ if (!list_empty(ad->dispatch) || as_dispatch_request(ad))
+ rq = list_entry_rq(ad->dispatch->next);
+
+ return rq;
+}
+
+/*
+ * add arq to rbtree and fifo
+ */
+static void as_add_request(struct as_data *ad, struct as_rq *arq)
+{
+ const int data_dir = rq_data_dir(arq->request);
+
+ arq->as_io_context = get_as_io_context();
+ if (arq->as_io_context) {
+ atomic_inc(&arq->as_io_context->nr_queued);
+
+ if (data_dir == READ)
+ as_update_iohist(arq->as_io_context);
+ }
+
+ as_add_arq_rb(ad, arq);
+
+ /*
+ * set expire time (only used for reads) and add to fifo list
+ */
+ arq->expires = jiffies + ad->fifo_expire[data_dir];
+ list_add_tail(&arq->fifo, &ad->fifo_list[data_dir]);
+ arq->state = AS_RQ_QUEUED;
+ as_update_arq(ad, arq); /* keep state machine up to date */
+}
+
+static void
+as_insert_request(request_queue_t *q, struct request *rq,
+ struct list_head *insert_here)
+{
+ struct as_data *ad = q->elevator.elevator_data;
+ struct as_rq *arq = RQ_DATA(rq);
+
+ if (unlikely(rq->flags & REQ_HARDBARRIER)) {
+ AS_INVALIDATE_HASH(ad);
+ q->last_merge = NULL;
+ }
+
+ if (unlikely(!blk_fs_request(rq))) {
+ if (!insert_here)
+ insert_here = ad->dispatch->prev;
+
+ list_add(&rq->queuelist, insert_here);
+
+ /* Stop anticipating - let this request get through */
+ if (!list_empty(ad->dispatch) && rq_data_dir(rq) == READ
+ && (ad->antic_status == ANTIC_WAIT_REQ
+ || ad->antic_status == ANTIC_WAIT_NEXT))
+ as_antic_stop(ad);
+
+ return;
+ }
+
+ if (rq_mergeable(rq)) {
+ as_add_arq_hash(ad, arq);
+
+ if (!q->last_merge)
+ q->last_merge = &rq->queuelist;
+ }
+
+ as_add_request(ad, arq);
+}
+
+/*
+ * as_queue_notready tells us weather or not as_next_request
+ * will return us a request or NULL. With the previous work conserving
+ * scheduler this API was designed around, if a queue had requests in it,
+ * as_next_request would return a request, and drivers seem to make
+ * that assumption
+ */
+static int as_queue_notready(request_queue_t *q)
+{
+ int ret = 0;
+ struct as_data *ad = q->elevator.elevator_data;
+
+ if (!list_empty(ad->dispatch))
+ goto out;
+
+ if (ad->antic_status == ANTIC_WAIT_REQ ||
+ ad->antic_status == ANTIC_WAIT_NEXT) {
+ ret = 1;
+ goto out;
+ }
+
+ if (!as_dispatch_request(ad)) {
+ ret = 1;
+ goto out;
+ }
+
+out:
+ return ret;
+}
+
+static struct request *
+as_former_request(request_queue_t *q, struct request *rq)
+{
+ struct as_rq *arq = RQ_DATA(rq);
+ struct rb_node *rbprev = rb_prev(&arq->rb_node);
+ struct request *ret = NULL;
+
+ if (rbprev)
+ ret = rb_entry_arq(rbprev)->request;
+
+ return ret;
+}
+
+static struct request *
+as_latter_request(request_queue_t *q, struct request *rq)
+{
+ struct as_rq *arq = RQ_DATA(rq);
+ struct rb_node *rbnext = rb_next(&arq->rb_node);
+ struct request *ret = NULL;
+
+ if (rbnext)
+ ret = rb_entry_arq(rbnext)->request;
+
+ return ret;
+}
+
+static int
+as_merge(request_queue_t *q, struct list_head **insert, struct bio *bio)
+{
+ struct as_data *ad = q->elevator.elevator_data;
+ struct request *__rq;
+ int ret;
+
+ /*
+ * try last_merge to avoid going to hash
+ */
+ ret = elv_try_last_merge(q, bio);
+ if (ret != ELEVATOR_NO_MERGE) {
+ __rq = list_entry_rq(q->last_merge);
+ goto out_insert;
+ }
+
+ /*
+ * see if the merge hash can satisfy a back merge
+ */
+ __rq = as_find_arq_hash(ad, bio->bi_sector);
+ if (__rq) {
+ BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector);
+
+ if (elv_rq_merge_ok(__rq, bio)) {
+ ret = ELEVATOR_BACK_MERGE;
+ goto out;
+ }
+ }
+
+ /*
+ * check for front merge
+ */
+ if (ad->front_merges) {
+ sector_t rb_key = bio->bi_sector + bio_sectors(bio);
+
+ __rq = as_find_arq_rb(ad, rb_key, bio_data_dir(bio));
+ if (__rq) {
+ BUG_ON(rb_key != rq_rb_key(__rq));
+
+ if (elv_rq_merge_ok(__rq, bio)) {
+ ret = ELEVATOR_FRONT_MERGE;
+ goto out;
+ }
+ }
+ }
+
+ return ELEVATOR_NO_MERGE;
+out:
+ q->last_merge = &__rq->queuelist;
+out_insert:
+ *insert = &__rq->queuelist;
+ return ret;
+}
+
+static void as_merged_request(request_queue_t *q, struct request *req)
+{
+ struct as_data *ad = q->elevator.elevator_data;
+ struct as_rq *arq = RQ_DATA(req);
+
+ /*
+ * hash always needs to be repositioned, key is end sector
+ */
+ as_del_arq_hash(arq);
+ as_add_arq_hash(ad, arq);
+
+ /*
+ * if the merge was a front merge, we need to reposition request
+ */
+ if (rq_rb_key(req) != arq->rb_key) {
+ as_del_arq_rb(ad, arq);
+ as_add_arq_rb(ad, arq);
+ /*
+ * Note! At this stage of this and the next function, our next
+ * request may not be optimal - eg the request may have "grown"
+ * behind the disk head. We currently don't bother adjusting.
+ */
+ }
+
+ q->last_merge = &req->queuelist;
+}
+
+static void
+as_merged_requests(request_queue_t *q, struct request *req,
+ struct request *next)
+{
+ struct as_data *ad = q->elevator.elevator_data;
+ struct as_rq *arq = RQ_DATA(req);
+ struct as_rq *anext = RQ_DATA(next);
+
+ BUG_ON(!arq);
+ BUG_ON(!anext);
+
+ /*
+ * reposition arq (this is the merged request) in hash, and in rbtree
+ * in case of a front merge
+ */
+ as_del_arq_hash(arq);
+ as_add_arq_hash(ad, arq);
+
+ if (rq_rb_key(req) != arq->rb_key) {
+ as_del_arq_rb(ad, arq);
+ as_add_arq_rb(ad, arq);
+ }
+
+ /*
+ * if anext expires before arq, assign its expire time to arq
+ * and move into anext position (anext will be deleted) in fifo
+ */
+ if (!list_empty(&arq->fifo) && !list_empty(&anext->fifo)) {
+ if (time_before(anext->expires, arq->expires)) {
+ list_move(&arq->fifo, &anext->fifo);
+ arq->expires = anext->expires;
+ /*
+ * Don't copy here but swap, because when anext is
+ * removed below, it must contain the unused context
+ */
+ swap_as_io_context(&arq->as_io_context,
+ &anext->as_io_context);
+ }
+ }
+
+ /*
+ * kill knowledge of next, this one is a goner
+ */
+ as_remove_queued_request(q, next);
+ put_as_io_context(&anext->as_io_context);
+}
+
+/*
+ * This is executed in a "deferred" process context, by kblockd. It calls the
+ * driver's request_fn so the driver can submit that request.
+ *
+ * IMPORTANT! This guy will reenter the elevator, so set up all queue global
+ * state before calling, and don't rely on any state over calls.
+ *
+ * FIXME! dispatch queue is not a queue at all!
+ */
+static void as_work_handler(void *data)
+{
+ struct request_queue *q = data;
+ unsigned long flags;
+
+ spin_lock_irqsave(q->queue_lock, flags);
+ if (!as_queue_notready(q))
+ q->request_fn(q);
+ spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+static void as_exit(request_queue_t *q, elevator_t *e)
+{
+ struct as_data *ad = e->elevator_data;
+ struct as_rq *arq;
+ struct request *rq;
+ int i;
+
+ del_timer_sync(&ad->antic_timer);
+ kblockd_flush();
+
+ BUG_ON(!list_empty(&ad->fifo_list[READ]));
+ BUG_ON(!list_empty(&ad->fifo_list[WRITE]));
+
+ for (i = READ; i <= WRITE; i++) {
+ struct request_list *rl = &q->rq[i];
+ struct list_head *entry;
+
+ list_for_each(entry, &rl->free) {
+ rq = list_entry_rq(entry);
+
+ if ((arq = RQ_DATA(rq)) == NULL)
+ continue;
+
+ rq->elevator_private = NULL;
+ kmem_cache_free(arq_pool, arq);
+ }
+ }
+
+ put_as_io_context(&ad->as_io_context);
+ kfree(ad->hash);
+ kfree(ad);
+}
+
+/*
+ * initialize elevator private data (as_data), and alloc a arq for
+ * each request on the free lists
+ */
+static int as_init(request_queue_t *q, elevator_t *e)
+{
+ struct as_data *ad;
+ struct as_rq *arq;
+ struct request *rq;
+ int i, ret = 0;
+
+ if (!arq_pool)
+ return -ENOMEM;
+
+ ad = kmalloc(sizeof(*ad), GFP_KERNEL);
+ if (!ad)
+ return -ENOMEM;
+ memset(ad, 0, sizeof(*ad));
+
+ ad->q = q; /* Identify what queue the data belongs to */
+
+ ad->hash = kmalloc(sizeof(struct list_head)*AS_HASH_ENTRIES,GFP_KERNEL);
+ if (!ad->hash) {
+ kfree(ad);
+ return -ENOMEM;
+ }
+
+ /* anticipatory scheduling helpers */
+ ad->antic_timer.function = as_antic_timeout;
+ ad->antic_timer.data = (unsigned long)q;
+ init_timer(&ad->antic_timer);
+ INIT_WORK(&ad->antic_work, as_work_handler, q);
+
+ for (i = 0; i < AS_HASH_ENTRIES; i++)
+ INIT_LIST_HEAD(&ad->hash[i]);
+
+ INIT_LIST_HEAD(&ad->fifo_list[READ]);
+ INIT_LIST_HEAD(&ad->fifo_list[WRITE]);
+ ad->sort_list[READ] = RB_ROOT;
+ ad->sort_list[WRITE] = RB_ROOT;
+ ad->dispatch = &q->queue_head;
+ ad->fifo_expire[READ] = read_expire;
+ ad->fifo_expire[WRITE] = write_expire;
+ ad->hash_valid_count = 1;
+ ad->front_merges = 1;
+ ad->antic_expire = antic_expire;
+ ad->batch_expire[READ] = read_batch_expire;
+ ad->batch_expire[WRITE] = write_batch_expire;
+ e->elevator_data = ad;
+
+ ad->current_batch_expires = jiffies + ad->batch_expire[READ];
+
+ for (i = READ; i <= WRITE; i++) {
+ struct request_list *rl = &q->rq[i];
+ struct list_head *entry;
+
+ list_for_each(entry, &rl->free) {
+ rq = list_entry_rq(entry);
+
+ arq = kmem_cache_alloc(arq_pool, GFP_KERNEL);
+ if (!arq) {
+ ret = -ENOMEM;
+ break;
+ }
+
+ memset(arq, 0, sizeof(*arq));
+ INIT_LIST_HEAD(&arq->fifo);
+ INIT_LIST_HEAD(&arq->hash);
+ RB_CLEAR(&arq->rb_node);
+ arq->request = rq;
+ rq->elevator_private = arq;
+ }
+ }
+
+ if (ret)
+ as_exit(q, e);
+
+ return ret;
+}
+
+/*
+ * sysfs parts below
+ */
+struct as_fs_entry {
+ struct attribute attr;
+ ssize_t (*show)(struct as_data *, char *);
+ ssize_t (*store)(struct as_data *, const char *, size_t);
+};
+
+static ssize_t
+as_var_show(unsigned int var, char *page)
+{
+ return sprintf(page, "%d\n", var);
+}
+
+static ssize_t
+as_var_store(unsigned long *var, const char *page, size_t count)
+{
+ char *p = (char *) page;
+
+ *var = simple_strtoul(p, &p, 10);
+ return count;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR) \
+static ssize_t __FUNC(struct as_data *ad, char *page) \
+{ \
+ return as_var_show(__VAR, (page)); \
+}
+SHOW_FUNCTION(as_readexpire_show, ad->fifo_expire[READ]);
+SHOW_FUNCTION(as_writeexpire_show, ad->fifo_expire[WRITE]);
+SHOW_FUNCTION(as_frontmerges_show, ad->front_merges);
+SHOW_FUNCTION(as_anticexpire_show, ad->antic_expire);
+SHOW_FUNCTION(as_read_batchexpire_show, ad->batch_expire[READ]);
+SHOW_FUNCTION(as_write_batchexpire_show, ad->batch_expire[WRITE]);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \
+static ssize_t __FUNC(struct as_data *ad, const char *page, size_t count) \
+{ \
+ int ret = as_var_store(__PTR, (page), count); \
+ if (*(__PTR) < (MIN)) \
+ *(__PTR) = (MIN); \
+ else if (*(__PTR) > (MAX)) \
+ *(__PTR) = (MAX); \
+ return ret; \
+}
+STORE_FUNCTION(as_readexpire_store, &ad->fifo_expire[READ], 0, INT_MAX);
+STORE_FUNCTION(as_writeexpire_store, &ad->fifo_expire[WRITE], 0, INT_MAX);
+STORE_FUNCTION(as_frontmerges_store, &ad->front_merges, 0, 1);
+STORE_FUNCTION(as_anticexpire_store, &ad->antic_expire, 0, INT_MAX);
+STORE_FUNCTION(as_read_batchexpire_store,
+ &ad->batch_expire[READ], 0, INT_MAX);
+STORE_FUNCTION(as_write_batchexpire_store,
+ &ad->batch_expire[WRITE], 0, INT_MAX);
+#undef STORE_FUNCTION
+
+static struct as_fs_entry as_readexpire_entry = {
+ .attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR },
+ .show = as_readexpire_show,
+ .store = as_readexpire_store,
+};
+static struct as_fs_entry as_writeexpire_entry = {
+ .attr = {.name = "write_expire", .mode = S_IRUGO | S_IWUSR },
+ .show = as_writeexpire_show,
+ .store = as_writeexpire_store,
+};
+static struct as_fs_entry as_frontmerges_entry = {
+ .attr = {.name = "front_merges", .mode = S_IRUGO | S_IWUSR },
+ .show = as_frontmerges_show,
+ .store = as_frontmerges_store,
+};
+static struct as_fs_entry as_anticexpire_entry = {
+ .attr = {.name = "antic_expire", .mode = S_IRUGO | S_IWUSR },
+ .show = as_anticexpire_show,
+ .store = as_anticexpire_store,
+};
+static struct as_fs_entry as_read_batchexpire_entry = {
+ .attr = {.name = "read_batch_expire", .mode = S_IRUGO | S_IWUSR },
+ .show = as_read_batchexpire_show,
+ .store = as_read_batchexpire_store,
+};
+static struct as_fs_entry as_write_batchexpire_entry = {
+ .attr = {.name = "write_batch_expire", .mode = S_IRUGO | S_IWUSR },
+ .show = as_write_batchexpire_show,
+ .store = as_write_batchexpire_store,
+};
+
+static struct attribute *default_attrs[] = {
+ &as_readexpire_entry.attr,
+ &as_writeexpire_entry.attr,
+ &as_frontmerges_entry.attr,
+ &as_anticexpire_entry.attr,
+ &as_read_batchexpire_entry.attr,
+ &as_write_batchexpire_entry.attr,
+ NULL,
+};
+
+#define to_as(atr) container_of((atr), struct as_fs_entry, attr)
+
+static ssize_t
+as_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
+{
+ elevator_t *e = container_of(kobj, elevator_t, kobj);
+ struct as_fs_entry *entry = to_as(attr);
+
+ if (!entry->show)
+ return 0;
+
+ return entry->show(e->elevator_data, page);
+}
+
+static ssize_t
+as_attr_store(struct kobject *kobj, struct attribute *attr,
+ const char *page, size_t length)
+{
+ elevator_t *e = container_of(kobj, elevator_t, kobj);
+ struct as_fs_entry *entry = to_as(attr);
+
+ if (!entry->store)
+ return -EINVAL;
+
+ return entry->store(e->elevator_data, page, length);
+}
+
+static struct sysfs_ops as_sysfs_ops = {
+ .show = as_attr_show,
+ .store = as_attr_store,
+};
+
+struct kobj_type as_ktype = {
+ .sysfs_ops = &as_sysfs_ops,
+ .default_attrs = default_attrs,
+};
+
+static int __init as_slab_setup(void)
+{
+ arq_pool = kmem_cache_create("as_arq", sizeof(struct as_rq),
+ 0, 0, NULL, NULL);
+
+ if (!arq_pool)
+ panic("as: can't init slab pool\n");
+
+ return 0;
+}
+
+subsys_initcall(as_slab_setup);
+
+elevator_t iosched_as = {
+ .elevator_merge_fn = as_merge,
+ .elevator_merged_fn = as_merged_request,
+ .elevator_merge_req_fn = as_merged_requests,
+ .elevator_next_req_fn = as_next_request,
+ .elevator_add_req_fn = as_insert_request,
+ .elevator_remove_req_fn = as_remove_request,
+ .elevator_queue_empty_fn = as_queue_notready,
+ .elevator_former_req_fn = as_former_request,
+ .elevator_latter_req_fn = as_latter_request,
+ .elevator_init_fn = as_init,
+ .elevator_exit_fn = as_exit,
+
+ .elevator_ktype = &as_ktype,
+};
+
+EXPORT_SYMBOL(iosched_as);
diff -puN drivers/block/Makefile~as-iosched drivers/block/Makefile
--- 25/drivers/block/Makefile~as-iosched 2003-04-01 02:33:28.000000000 -0800
+++ 25-akpm/drivers/block/Makefile 2003-04-01 02:33:28.000000000 -0800
@@ -13,7 +13,8 @@
# kblockd threads
#
-obj-y := elevator.o ll_rw_blk.o ioctl.o genhd.o scsi_ioctl.o deadline-iosched.o
+obj-y := elevator.o ll_rw_blk.o ioctl.o genhd.o scsi_ioctl.o \
+ deadline-iosched.o as-iosched.o
obj-$(CONFIG_MAC_FLOPPY) += swim3.o
obj-$(CONFIG_BLK_DEV_FD) += floppy.o
diff -puN include/linux/elevator.h~as-iosched include/linux/elevator.h
--- 25/include/linux/elevator.h~as-iosched 2003-04-01 02:33:28.000000000 -0800
+++ 25-akpm/include/linux/elevator.h 2003-04-01 02:33:28.000000000 -0800
@@ -73,6 +73,11 @@ extern elevator_t elevator_noop;
*/
extern elevator_t iosched_deadline;
+/*
+ * anticipatory I/O scheduler
+ */
+extern elevator_t iosched_as;
+
extern int elevator_init(request_queue_t *, elevator_t *);
extern void elevator_exit(request_queue_t *);
extern inline int bio_rq_in_between(struct bio *, struct request *, struct list_head *);
diff -puN drivers/block/ll_rw_blk.c~as-iosched drivers/block/ll_rw_blk.c
--- 25/drivers/block/ll_rw_blk.c~as-iosched 2003-04-01 02:33:28.000000000 -0800
+++ 25-akpm/drivers/block/ll_rw_blk.c 2003-04-01 02:33:28.000000000 -0800
@@ -1220,6 +1220,18 @@ nomem:
static int __make_request(request_queue_t *, struct bio *);
+static elevator_t *chosen_elevator = &iosched_as;
+
+static int __init elevator_setup(char *str)
+{
+ if (!strcmp(str, "deadline")) {
+ chosen_elevator = &iosched_deadline;
+ printk("elevator: cfq\n");
+ }
+ return 1;
+}
+__setup("elevator=", elevator_setup);
+
/**
* blk_init_queue - prepare a request queue for use with a block device
* @q: The &request_queue_t to be initialised
@@ -1255,7 +1267,12 @@ int blk_init_queue(request_queue_t *q, r
if (blk_init_free_list(q))
return -ENOMEM;
- if ((ret = elevator_init(q, &iosched_deadline))) {
+ if (chosen_elevator == &iosched_deadline)
+ printk("deadline elevator\n");
+ else if (chosen_elevator == &iosched_as)
+ printk("anticipatory scheduling elevator\n");
+
+ if ((ret = elevator_init(q, chosen_elevator))) {
blk_cleanup_queue(q);
return ret;
}
diff -puN include/linux/sched.h~as-iosched include/linux/sched.h
--- 25/include/linux/sched.h~as-iosched 2003-04-01 02:33:28.000000000 -0800
+++ 25-akpm/include/linux/sched.h 2003-04-01 02:33:28.000000000 -0800
@@ -313,6 +313,8 @@ struct k_itimer {
};
+struct as_io_context; /* Anticipatory scheduler */
+void exit_as_io_context(void);
struct task_struct {
volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */
@@ -436,6 +438,8 @@ struct task_struct {
struct dentry *proc_dentry;
struct backing_dev_info *backing_dev_info;
+ struct as_io_context *as_io_context;
+
unsigned long ptrace_message;
siginfo_t *last_siginfo; /* For ptrace use. */
};
diff -puN kernel/exit.c~as-iosched kernel/exit.c
--- 25/kernel/exit.c~as-iosched 2003-04-01 02:33:28.000000000 -0800
+++ 25-akpm/kernel/exit.c 2003-04-01 02:33:28.000000000 -0800
@@ -694,6 +694,8 @@ NORET_TYPE void do_exit(long code)
panic("Attempted to kill the idle task!");
if (unlikely(tsk->pid == 1))
panic("Attempted to kill init!");
+ if (tsk->as_io_context)
+ exit_as_io_context();
tsk->flags |= PF_EXITING;
del_timer_sync(&tsk->real_timer);
diff -puN kernel/fork.c~as-iosched kernel/fork.c
--- 25/kernel/fork.c~as-iosched 2003-04-01 02:33:28.000000000 -0800
+++ 25-akpm/kernel/fork.c 2003-04-01 02:33:28.000000000 -0800
@@ -856,6 +856,7 @@ static struct task_struct *copy_process(
p->lock_depth = -1; /* -1 = no lock */
p->start_time = get_jiffies_64();
p->security = NULL;
+ p->as_io_context = NULL;
retval = -ENOMEM;
if (security_task_alloc(p))
_