diff options
Diffstat (limited to 'libdde-linux26/contrib/block/as-iosched.c')
| -rw-r--r-- | libdde-linux26/contrib/block/as-iosched.c | 1526 |
1 files changed, 1526 insertions, 0 deletions
diff --git a/libdde-linux26/contrib/block/as-iosched.c b/libdde-linux26/contrib/block/as-iosched.c new file mode 100644 index 00000000..5b363ced --- /dev/null +++ b/libdde-linux26/contrib/block/as-iosched.c @@ -0,0 +1,1526 @@ +/* + * Anticipatory & deadline i/o scheduler. + * + * Copyright (C) 2002 Jens Axboe <axboe@kernel.dk> + * Nick Piggin <nickpiggin@yahoo.com.au> + * + */ +#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/interrupt.h> + +#include <ddekit/timer.h> + +#define REQ_SYNC 1 +#define REQ_ASYNC 0 + +/* + * See Documentation/block/as-iosched.txt + */ + +/* + * max time before a read is submitted. + */ +#define default_read_expire (HZ / 8) + +/* + * ditto for writes, these limits are not hard, even + * if the disk is capable of satisfying them. + */ +#define default_write_expire (HZ / 4) + +/* + * 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. + */ +#define default_read_batch_expire (HZ / 2) + +/* + * write_batch_expire describes how long we want a stream of writes to run for. + * This is not a hard limit, but a target we set for the auto-tuning thingy. + * See, the problem is: we can send a lot of writes to disk cache / TCQ in + * a short amount of time... + */ +#define default_write_batch_expire (HZ / 8) + +/* + * max time we may wait to anticipate a read (default around 6ms) + */ +#define default_antic_expire ((HZ / 150) ? HZ / 150 : 1) + +/* + * Keep track of up to 20ms thinktimes. We can go as big as we like here, + * however huge values tend to interfere and not decay fast enough. A program + * might be in a non-io phase of operation. Waiting on user input for example, + * or doing a lengthy computation. A small penalty can be justified there, and + * will still catch out those processes that constantly have large thinktimes. + */ +#define MAX_THINKTIME (HZ/50UL) + +/* Bits in as_io_context.state */ +enum as_io_states { + AS_TASK_RUNNING=0, /* Process has not exited */ + AS_TASK_IOSTARTED, /* Process has started some IO */ + AS_TASK_IORUNNING, /* Process has completed some IO */ +}; + +enum anticipation_status { + 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 */ +}; + +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 request *next_rq[2]; /* next in sort order */ + sector_t last_sector[2]; /* last REQ_SYNC & REQ_ASYNC sectors */ + + unsigned long exit_prob; /* probability a task will exit while + being waited on */ + unsigned long exit_no_coop; /* probablility an exited task will + not be part of a later cooperating + request */ + unsigned long new_ttime_total; /* mean thinktime on new proc */ + unsigned long new_ttime_mean; + u64 new_seek_total; /* mean seek on new proc */ + sector_t new_seek_mean; + + unsigned long current_batch_expires; + unsigned long last_check_fifo[2]; + int changed_batch; /* 1: waiting for old batch to end */ + int new_batch; /* 1: waiting on first read complete */ + int batch_data_dir; /* current batch REQ_SYNC / REQ_ASYNC */ + int write_batch_count; /* max # of reqs in a write batch */ + int current_write_count; /* how many requests left this batch */ + int write_batch_idled; /* has the write batch gone idle? */ + + enum anticipation_status 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 io_context *io_context; /* Identify the expected process */ + int ioc_finished; /* IO associated with io_context is finished */ + int nr_dispatched; + + /* + * settings that change how the i/o scheduler behaves + */ + unsigned long fifo_expire[2]; + unsigned long batch_expire[2]; + unsigned long antic_expire; +}; + +/* + * 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 */ + AS_RQ_PRESCHED, /* Debug poisoning for requests being used */ + AS_RQ_REMOVED, + AS_RQ_MERGED, + AS_RQ_POSTSCHED, /* when they shouldn't be */ +}; + +#define RQ_IOC(rq) ((struct io_context *) (rq)->elevator_private) +#define RQ_STATE(rq) ((enum arq_state)(rq)->elevator_private2) +#define RQ_SET_STATE(rq, state) ((rq)->elevator_private2 = (void *) state) + +static DEFINE_PER_CPU(unsigned long, ioc_count); +static struct completion *ioc_gone; +static DEFINE_SPINLOCK(ioc_gone_lock); + +static void as_move_to_dispatch(struct as_data *ad, struct request *rq); +static void as_antic_stop(struct as_data *ad); + +/* + * IO Context helper functions + */ + +/* Called to deallocate the as_io_context */ +static void free_as_io_context(struct as_io_context *aic) +{ + kfree(aic); + elv_ioc_count_dec(ioc_count); + if (ioc_gone) { + /* + * AS scheduler is exiting, grab exit lock and check + * the pending io context count. If it hits zero, + * complete ioc_gone and set it back to NULL. + */ + spin_lock(&ioc_gone_lock); + if (ioc_gone && !elv_ioc_count_read(ioc_count)) { + complete(ioc_gone); + ioc_gone = NULL; + } + spin_unlock(&ioc_gone_lock); + } +} + +static void as_trim(struct io_context *ioc) +{ + spin_lock_irq(&ioc->lock); + if (ioc->aic) + free_as_io_context(ioc->aic); + ioc->aic = NULL; + spin_unlock_irq(&ioc->lock); +} + +/* Called when the task exits */ +static void exit_as_io_context(struct as_io_context *aic) +{ + WARN_ON(!test_bit(AS_TASK_RUNNING, &aic->state)); + clear_bit(AS_TASK_RUNNING, &aic->state); +} + +static struct as_io_context *alloc_as_io_context(void) +{ + struct as_io_context *ret; + + ret = kmalloc(sizeof(*ret), GFP_ATOMIC); + if (ret) { + ret->dtor = free_as_io_context; + ret->exit = exit_as_io_context; + ret->state = 1 << AS_TASK_RUNNING; + atomic_set(&ret->nr_queued, 0); + atomic_set(&ret->nr_dispatched, 0); + spin_lock_init(&ret->lock); + ret->ttime_total = 0; + ret->ttime_samples = 0; + ret->ttime_mean = 0; + ret->seek_total = 0; + ret->seek_samples = 0; + ret->seek_mean = 0; + elv_ioc_count_inc(ioc_count); + } + + return ret; +} + +/* + * If the current task has no AS IO context then create one and initialise it. + * Then take a ref on the task's io context and return it. + */ +static struct io_context *as_get_io_context(int node) +{ + struct io_context *ioc = get_io_context(GFP_ATOMIC, node); + if (ioc && !ioc->aic) { + ioc->aic = alloc_as_io_context(); + if (!ioc->aic) { + put_io_context(ioc); + ioc = NULL; + } + } + return ioc; +} + +static void as_put_io_context(struct request *rq) +{ + struct as_io_context *aic; + + if (unlikely(!RQ_IOC(rq))) + return; + + aic = RQ_IOC(rq)->aic; + + if (rq_is_sync(rq) && aic) { + unsigned long flags; + + spin_lock_irqsave(&aic->lock, flags); + set_bit(AS_TASK_IORUNNING, &aic->state); + aic->last_end_request = jiffies; + spin_unlock_irqrestore(&aic->lock, flags); + } + + put_io_context(RQ_IOC(rq)); +} + +/* + * rb tree support functions + */ +#define RQ_RB_ROOT(ad, rq) (&(ad)->sort_list[rq_is_sync((rq))]) + +static void as_add_rq_rb(struct as_data *ad, struct request *rq) +{ + struct request *alias; + + while ((unlikely(alias = elv_rb_add(RQ_RB_ROOT(ad, rq), rq)))) { + as_move_to_dispatch(ad, alias); + as_antic_stop(ad); + } +} + +static inline void as_del_rq_rb(struct as_data *ad, struct request *rq) +{ + elv_rb_del(RQ_RB_ROOT(ad, rq), rq); +} + +/* + * IO Scheduler proper + */ + +#define MAXBACK (1024 * 1024) /* + * Maximum distance the disk will go backward + * for a request. + */ + +#define BACK_PENALTY 2 + +/* + * 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 request * +as_choose_req(struct as_data *ad, struct request *rq1, struct request *rq2) +{ + 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 (rq1 == NULL || rq1 == rq2) + return rq2; + if (rq2 == NULL) + return rq1; + + data_dir = rq_is_sync(rq1); + + last = ad->last_sector[data_dir]; + s1 = rq1->sector; + s2 = rq2->sector; + + BUG_ON(data_dir != rq_is_sync(rq2)); + + /* + * 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. + */ + if (s1 >= last) + d1 = s1 - last; + else if (s1+maxback >= last) + d1 = (last - s1)*BACK_PENALTY; + else { + r1_wrap = 1; + d1 = 0; /* shut up, gcc */ + } + + if (s2 >= last) + d2 = s2 - last; + else if (s2+maxback >= last) + d2 = (last - s2)*BACK_PENALTY; + else { + r2_wrap = 1; + d2 = 0; + } + + /* Found required data */ + if (!r1_wrap && r2_wrap) + return rq1; + else if (!r2_wrap && r1_wrap) + return rq2; + else if (r1_wrap && r2_wrap) { + /* both behind the head */ + if (s1 <= s2) + return rq1; + else + return rq2; + } + + /* Both requests in front of the head */ + if (d1 < d2) + return rq1; + else if (d2 < d1) + return rq2; + else { + if (s1 >= s2) + return rq1; + else + return rq2; + } +} + +/* + * as_find_next_rq finds the next request after @prev in elevator order. + * this with as_choose_req form the basis for how the scheduler chooses + * what request to process next. Anticipation works on top of this. + */ +static struct request * +as_find_next_rq(struct as_data *ad, struct request *last) +{ + struct rb_node *rbnext = rb_next(&last->rb_node); + struct rb_node *rbprev = rb_prev(&last->rb_node); + struct request *next = NULL, *prev = NULL; + + BUG_ON(RB_EMPTY_NODE(&last->rb_node)); + + if (rbprev) + prev = rb_entry_rq(rbprev); + + if (rbnext) + next = rb_entry_rq(rbnext); + else { + const int data_dir = rq_is_sync(last); + + rbnext = rb_first(&ad->sort_list[data_dir]); + if (rbnext && rbnext != &last->rb_node) + next = rb_entry_rq(rbnext); + } + + return as_choose_req(ad, next, prev); +} + +/* + * 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; + + 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) { + if (!ad->io_context || ad->ioc_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->q, &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; + unsigned long flags; + + spin_lock_irqsave(q->queue_lock, flags); + if (ad->antic_status == ANTIC_WAIT_REQ + || ad->antic_status == ANTIC_WAIT_NEXT) { + struct as_io_context *aic; + spin_lock(&ad->io_context->lock); + aic = ad->io_context->aic; + + ad->antic_status = ANTIC_FINISHED; + kblockd_schedule_work(q, &ad->antic_work); + + if (aic->ttime_samples == 0) { + /* process anticipated on has exited or timed out*/ + ad->exit_prob = (7*ad->exit_prob + 256)/8; + } + if (!test_bit(AS_TASK_RUNNING, &aic->state)) { + /* process not "saved" by a cooperating request */ + ad->exit_no_coop = (7*ad->exit_no_coop + 256)/8; + } + spin_unlock(&ad->io_context->lock); + } + spin_unlock_irqrestore(q->queue_lock, flags); +} + +static void as_update_thinktime(struct as_data *ad, struct as_io_context *aic, + unsigned long ttime) +{ + /* fixed point: 1.0 == 1<<8 */ + if (aic->ttime_samples == 0) { + ad->new_ttime_total = (7*ad->new_ttime_total + 256*ttime) / 8; + ad->new_ttime_mean = ad->new_ttime_total / 256; + + ad->exit_prob = (7*ad->exit_prob)/8; + } + aic->ttime_samples = (7*aic->ttime_samples + 256) / 8; + aic->ttime_total = (7*aic->ttime_total + 256*ttime) / 8; + aic->ttime_mean = (aic->ttime_total + 128) / aic->ttime_samples; +} + +static void as_update_seekdist(struct as_data *ad, struct as_io_context *aic, + sector_t sdist) +{ + u64 total; + + if (aic->seek_samples == 0) { + ad->new_seek_total = (7*ad->new_seek_total + 256*(u64)sdist)/8; + ad->new_seek_mean = ad->new_seek_total / 256; + } + + /* + * Don't allow the seek distance to get too large from the + * odd fragment, pagein, etc + */ + if (aic->seek_samples <= 60) /* second&third seek */ + sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*1024); + else + sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*64); + + aic->seek_samples = (7*aic->seek_samples + 256) / 8; + aic->seek_total = (7*aic->seek_total + (u64)256*sdist) / 8; + total = aic->seek_total + (aic->seek_samples/2); + do_div(total, aic->seek_samples); + aic->seek_mean = (sector_t)total; +} + +/* + * as_update_iohist keeps a decaying histogram of IO thinktimes, and + * updates @aic->ttime_mean based on that. It is called when a new + * request is queued. + */ +static void as_update_iohist(struct as_data *ad, struct as_io_context *aic, + struct request *rq) +{ + int data_dir = rq_is_sync(rq); + unsigned long thinktime = 0; + sector_t seek_dist; + + if (aic == NULL) + return; + + if (data_dir == REQ_SYNC) { + unsigned long in_flight = atomic_read(&aic->nr_queued) + + atomic_read(&aic->nr_dispatched); + spin_lock(&aic->lock); + if (test_bit(AS_TASK_IORUNNING, &aic->state) || + test_bit(AS_TASK_IOSTARTED, &aic->state)) { + /* Calculate read -> read thinktime */ + if (test_bit(AS_TASK_IORUNNING, &aic->state) + && in_flight == 0) { + thinktime = jiffies - aic->last_end_request; + thinktime = min(thinktime, MAX_THINKTIME-1); + } + as_update_thinktime(ad, aic, thinktime); + + /* Calculate read -> read seek distance */ + if (aic->last_request_pos < rq->sector) + seek_dist = rq->sector - aic->last_request_pos; + else + seek_dist = aic->last_request_pos - rq->sector; + as_update_seekdist(ad, aic, seek_dist); + } + aic->last_request_pos = rq->sector + rq->nr_sectors; + set_bit(AS_TASK_IOSTARTED, &aic->state); + spin_unlock(&aic->lock); + } +} + +/* + * 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_io_context *aic, + struct request *rq) +{ + unsigned long delay; /* jiffies */ + sector_t last = ad->last_sector[ad->batch_data_dir]; + sector_t next = rq->sector; + sector_t delta; /* acceptable close offset (in sectors) */ + sector_t s; + + if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished) + delay = 0; + else + delay = jiffies - ad->antic_start; + + if (delay == 0) + delta = 8192; + else if (delay <= (20 * HZ / 1000) && delay <= ad->antic_expire) + delta = 8192 << delay; + else + return 1; + + if ((last <= next + (delta>>1)) && (next <= last + delta)) + return 1; + + if (last < next) + s = next - last; + else + s = last - next; + + if (aic->seek_samples == 0) { + /* + * Process has just started IO. Use past statistics to + * gauge success possibility + */ + if (ad->new_seek_mean > s) { + /* this request is better than what we're expecting */ + return 1; + } + + } else { + if (aic->seek_mean > s) { + /* this request is better than what we're expecting */ + return 1; + } + } + + return 0; +} + +/* + * 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 exited, 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 request *rq) +{ + struct io_context *ioc; + struct as_io_context *aic; + + ioc = ad->io_context; + BUG_ON(!ioc); + spin_lock(&ioc->lock); + + if (rq && ioc == RQ_IOC(rq)) { + /* request from same process */ + spin_unlock(&ioc->lock); + return 1; + } + + if (ad->ioc_finished && as_antic_expired(ad)) { + /* + * In this situation status should really be FINISHED, + * however the timer hasn't had the chance to run yet. + */ + spin_unlock(&ioc->lock); + return 1; + } + + aic = ioc->aic; + if (!aic) { + spin_unlock(&ioc->lock); + return 0; + } + + if (atomic_read(&aic->nr_queued) > 0) { + /* process has more requests queued */ + spin_unlock(&ioc->lock); + return 1; + } + + if (atomic_read(&aic->nr_dispatched) > 0) { + /* process has more requests dispatched */ + spin_unlock(&ioc->lock); + return 1; + } + + if (rq && rq_is_sync(rq) && as_close_req(ad, aic, rq)) { + /* + * Found a close request that is not one of ours. + * + * This makes close requests from another process update + * our IO history. Is generally useful when there are + * two or more cooperating processes working in the same + * area. + */ + if (!test_bit(AS_TASK_RUNNING, &aic->state)) { + if (aic->ttime_samples == 0) + ad->exit_prob = (7*ad->exit_prob + 256)/8; + + ad->exit_no_coop = (7*ad->exit_no_coop)/8; + } + + as_update_iohist(ad, aic, rq); + spin_unlock(&ioc->lock); + return 1; + } + + if (!test_bit(AS_TASK_RUNNING, &aic->state)) { + /* process anticipated on has exited */ + if (aic->ttime_samples == 0) + ad->exit_prob = (7*ad->exit_prob + 256)/8; + + if (ad->exit_no_coop > 128) { + spin_unlock(&ioc->lock); + return 1; + } + } + + if (aic->ttime_samples == 0) { + if (ad->new_ttime_mean > ad->antic_expire) { + spin_unlock(&ioc->lock); + return 1; + } + if (ad->exit_prob * ad->exit_no_coop > 128*256) { + spin_unlock(&ioc->lock); + return 1; + } + } else if (aic->ttime_mean > ad->antic_expire) { + /* the process thinks too much between requests */ + spin_unlock(&ioc->lock); + return 1; + } + spin_unlock(&ioc->lock); + return 0; +} + +/* + * as_can_anticipate indicates whether we should either run rq + * or keep anticipating a better request. + */ +static int as_can_anticipate(struct as_data *ad, struct request *rq) +{ +#if 0 /* disable for now, we need to check tag level as well */ + /* + * SSD device without seek penalty, disable idling + */ + if (blk_queue_nonrot(ad->q)) axman + return 0; +#endif + + if (!ad->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 (as_can_break_anticipation(ad, rq)) + /* + * 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_rq must be called whenever a request (rq) 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_rq(struct as_data *ad, struct request *rq) +{ + const int data_dir = rq_is_sync(rq); + + /* keep the next_rq cache up to date */ + ad->next_rq[data_dir] = as_choose_req(ad, rq, ad->next_rq[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->antic_status == ANTIC_WAIT_REQ + || ad->antic_status == ANTIC_WAIT_NEXT) { + if (as_can_break_anticipation(ad, rq)) + as_antic_stop(ad); + } +} + +/* + * Gathers timings and resizes the write batch automatically + */ +static void update_write_batch(struct as_data *ad) +{ + unsigned long batch = ad->batch_expire[REQ_ASYNC]; + long write_time; + + write_time = (jiffies - ad->current_batch_expires) + batch; + if (write_time < 0) + write_time = 0; + + if (write_time > batch && !ad->write_batch_idled) { + if (write_time > batch * 3) + ad->write_batch_count /= 2; + else + ad->write_batch_count--; + } else if (write_time < batch && ad->current_write_count == 0) { + if (batch > write_time * 3) + ad->write_batch_count *= 2; + else + ad->write_batch_count++; + } + + if (ad->write_batch_count < 1) + ad->write_batch_count = 1; +} + +/* + * as_completed_request 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_completed_request(struct request_queue *q, struct request *rq) +{ + struct as_data *ad = q->elevator->elevator_data; + + WARN_ON(!list_empty(&rq->queuelist)); + + if (RQ_STATE(rq) != AS_RQ_REMOVED) { + WARN(1, "rq->state %d\n", RQ_STATE(rq)); + goto out; + } + + if (ad->changed_batch && ad->nr_dispatched == 1) { + ad->current_batch_expires = jiffies + + ad->batch_expire[ad->batch_data_dir]; + kblockd_schedule_work(q, &ad->antic_work); + ad->changed_batch = 0; + + if (ad->batch_data_dir == REQ_SYNC) + ad->new_batch = 1; + } + WARN_ON(ad->nr_dispatched == 0); + ad->nr_dispatched--; + + /* + * Start counting the batch from when a request of that direction is + * actually serviced. This should help devices with big TCQ windows + * and writeback caches + */ + if (ad->new_batch && ad->batch_data_dir == rq_is_sync(rq)) { + update_write_batch(ad); + ad->current_batch_expires = jiffies + + ad->batch_expire[REQ_SYNC]; + ad->new_batch = 0; + } + + if (ad->io_context == RQ_IOC(rq) && ad->io_context) { + ad->antic_start = jiffies; + ad->ioc_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_put_io_context(rq); +out: + RQ_SET_STATE(rq, AS_RQ_POSTSCHED); +} + +/* + * 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(struct request_queue *q, + struct request *rq) +{ + const int data_dir = rq_is_sync(rq); + struct as_data *ad = q->elevator->elevator_data; + struct io_context *ioc; + + WARN_ON(RQ_STATE(rq) != AS_RQ_QUEUED); + + ioc = RQ_IOC(rq); + if (ioc && ioc->aic) { + BUG_ON(!atomic_read(&ioc->aic->nr_queued)); + atomic_dec(&ioc->aic->nr_queued); + } + + /* + * Update the "next_rq" cache if we are about to remove its + * entry + */ + if (ad->next_rq[data_dir] == rq) + ad->next_rq[data_dir] = as_find_next_rq(ad, rq); + + rq_fifo_clear(rq); + as_del_rq_rb(ad, rq); +} + +/* + * as_fifo_expired returns 0 if there are no expired requests 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 request *rq; + 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; + + rq = rq_entry_fifo(ad->fifo_list[adir].next); + + return time_after(jiffies, rq_fifo_time(rq)); +} + +/* + * 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) +{ + if (ad->changed_batch || ad->new_batch) + return 0; + + if (ad->batch_data_dir == REQ_SYNC) + /* TODO! add a check so a complete fifo gets written? */ + return time_after(jiffies, ad->current_batch_expires); + + return time_after(jiffies, ad->current_batch_expires) + || ad->current_write_count == 0; +} + +/* + * move an entry to dispatch queue + */ +static void as_move_to_dispatch(struct as_data *ad, struct request *rq) +{ + const int data_dir = rq_is_sync(rq); + + BUG_ON(RB_EMPTY_NODE(&rq->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_rq + */ + ad->last_sector[data_dir] = rq->sector + rq->nr_sectors; + + if (data_dir == REQ_SYNC) { + struct io_context *ioc = RQ_IOC(rq); + /* In case we have to anticipate after this */ + copy_io_context(&ad->io_context, &ioc); + } else { + if (ad->io_context) { + put_io_context(ad->io_context); + ad->io_context = NULL; + } + + if (ad->current_write_count != 0) + ad->current_write_count--; + } + ad->ioc_finished = 0; + + ad->next_rq[data_dir] = as_find_next_rq(ad, rq); + + /* + * take it off the sort and fifo list, add to dispatch queue + */ + as_remove_queued_request(ad->q, rq); + WARN_ON(RQ_STATE(rq) != AS_RQ_QUEUED); + + elv_dispatch_sort(ad->q, rq); + + RQ_SET_STATE(rq, AS_RQ_DISPATCHED); + if (RQ_IOC(rq) && RQ_IOC(rq)->aic) + atomic_inc(&RQ_IOC(rq)->aic->nr_dispatched); + ad->nr_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 request_queue *q, int force) +{ + struct as_data *ad = q->elevator->elevator_data; + const int reads = !list_empty(&ad->fifo_list[REQ_SYNC]); + const int writes = !list_empty(&ad->fifo_list[REQ_ASYNC]); + struct request *rq; + + if (unlikely(force)) { + /* + * Forced dispatch, accounting is useless. Reset + * accounting states and dump fifo_lists. Note that + * batch_data_dir is reset to REQ_SYNC to avoid + * screwing write batch accounting as write batch + * accounting occurs on W->R transition. + */ + int dispatched = 0; + + ad->batch_data_dir = REQ_SYNC; + ad->changed_batch = 0; + ad->new_batch = 0; + + while (ad->next_rq[REQ_SYNC]) { + as_move_to_dispatch(ad, ad->next_rq[REQ_SYNC]); + dispatched++; + } + ad->last_check_fifo[REQ_SYNC] = jiffies; + + while (ad->next_rq[REQ_ASYNC]) { + as_move_to_dispatch(ad, ad->next_rq[REQ_ASYNC]); + dispatched++; + } + ad->last_check_fifo[REQ_ASYNC] = jiffies; + + return dispatched; + } + + /* Signal that the write batch was uncontended, so we can't time it */ + if (ad->batch_data_dir == REQ_ASYNC && !reads) { + if (ad->current_write_count == 0 || !writes) + ad->write_batch_idled = 1; + } + + if (!(reads || writes) + || ad->antic_status == ANTIC_WAIT_REQ + || ad->antic_status == ANTIC_WAIT_NEXT + || ad->changed_batch) + return 0; + + if (!(reads && writes && as_batch_expired(ad))) { + /* + * batch is still running or no reads or no writes + */ + rq = ad->next_rq[ad->batch_data_dir]; + + if (ad->batch_data_dir == REQ_SYNC && ad->antic_expire) { + if (as_fifo_expired(ad, REQ_SYNC)) + goto fifo_expired; + + if (as_can_anticipate(ad, rq)) { + as_antic_waitreq(ad); + return 0; + } + } + + if (rq) { + /* we have a "next request" */ + if (reads && !writes) + ad->current_batch_expires = + jiffies + ad->batch_expire[REQ_SYNC]; + 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_ROOT(&ad->sort_list[REQ_SYNC])); + + if (writes && ad->batch_data_dir == REQ_SYNC) + /* + * Last batch was a read, switch to writes + */ + goto dispatch_writes; + + if (ad->batch_data_dir == REQ_ASYNC) { + WARN_ON(ad->new_batch); + ad->changed_batch = 1; + } + ad->batch_data_dir = REQ_SYNC; + rq = rq_entry_fifo(ad->fifo_list[REQ_SYNC].next); + ad->last_check_fifo[ad->batch_data_dir] = jiffies; + goto dispatch_request; + } + + /* + * the last batch was a read + */ + + if (writes) { +dispatch_writes: + BUG_ON(RB_EMPTY_ROOT(&ad->sort_list[REQ_ASYNC])); + + if (ad->batch_data_dir == REQ_SYNC) { + ad->changed_batch = 1; + + /* + * new_batch might be 1 when the queue runs out of + * reads. A subsequent submission of a write might + * cause a change of batch before the read is finished. + */ + ad->new_batch = 0; + } + ad->batch_data_dir = REQ_ASYNC; + ad->current_write_count = ad->write_batch_count; + ad->write_batch_idled = 0; + rq = rq_entry_fifo(ad->fifo_list[REQ_ASYNC].next); + ad->last_check_fifo[REQ_ASYNC] = jiffies; + 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: + rq = rq_entry_fifo(ad->fifo_list[ad->batch_data_dir].next); + } + + if (ad->changed_batch) { + WARN_ON(ad->new_batch); + + if (ad->nr_dispatched) + return 0; + + if (ad->batch_data_dir == REQ_ASYNC) + ad->current_batch_expires = jiffies + + ad->batch_expire[REQ_ASYNC]; + else + ad->new_batch = 1; + + ad->changed_batch = 0; + } + + /* + * rq is the selected appropriate request. + */ + as_move_to_dispatch(ad, rq); + + return 1; +} + +/* + * add rq to rbtree and fifo + */ +static void as_add_request(struct request_queue *q, struct request *rq) +{ + struct as_data *ad = q->elevator->elevator_data; + int data_dir; + + RQ_SET_STATE(rq, AS_RQ_NEW); + + data_dir = rq_is_sync(rq); + + rq->elevator_private = as_get_io_context(q->node); + + if (RQ_IOC(rq)) { + as_update_iohist(ad, RQ_IOC(rq)->aic, rq); + atomic_inc(&RQ_IOC(rq)->aic->nr_queued); + } + + as_add_rq_rb(ad, rq); + + /* + * set expire time and add to fifo list + */ + rq_set_fifo_time(rq, jiffies + ad->fifo_expire[data_dir]); + list_add_tail(&rq->queuelist, &ad->fifo_list[data_dir]); + + as_update_rq(ad, rq); /* keep state machine up to date */ + RQ_SET_STATE(rq, AS_RQ_QUEUED); +} + +static void as_activate_request(struct request_queue *q, struct request *rq) +{ + WARN_ON(RQ_STATE(rq) != AS_RQ_DISPATCHED); + RQ_SET_STATE(rq, AS_RQ_REMOVED); + if (RQ_IOC(rq) && RQ_IOC(rq)->aic) + atomic_dec(&RQ_IOC(rq)->aic->nr_dispatched); +} + +static void as_deactivate_request(struct request_queue *q, struct request *rq) +{ + WARN_ON(RQ_STATE(rq) != AS_RQ_REMOVED); + RQ_SET_STATE(rq, AS_RQ_DISPATCHED); + if (RQ_IOC(rq) && RQ_IOC(rq)->aic) + atomic_inc(&RQ_IOC(rq)->aic->nr_dispatched); +} + +/* + * as_queue_empty tells us if there are requests left in the device. It may + * not be the case that a driver can get the next request even if the queue + * is not empty - it is used in the block layer to check for plugging and + * merging opportunities + */ +static int as_queue_empty(struct request_queue *q) +{ + struct as_data *ad = q->elevator->elevator_data; + + return list_empty(&ad->fifo_list[REQ_ASYNC]) + && list_empty(&ad->fifo_list[REQ_SYNC]); +} + +static int +as_merge(struct request_queue *q, struct request **req, struct bio *bio) +{ + struct as_data *ad = q->elevator->elevator_data; + sector_t rb_key = bio->bi_sector + bio_sectors(bio); + struct request *__rq; + + /* + * check for front merge + */ + __rq = elv_rb_find(&ad->sort_list[bio_data_dir(bio)], rb_key); + if (__rq && elv_rq_merge_ok(__rq, bio)) { + *req = __rq; + return ELEVATOR_FRONT_MERGE; + } + + return ELEVATOR_NO_MERGE; +} + +static void as_merged_request(struct request_queue *q, struct request *req, + int type) +{ + struct as_data *ad = q->elevator->elevator_data; + + /* + * if the merge was a front merge, we need to reposition request + */ + if (type == ELEVATOR_FRONT_MERGE) { + as_del_rq_rb(ad, req); + as_add_rq_rb(ad, req); + /* + * 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. + */ + } +} + +static void as_merged_requests(struct request_queue *q, struct request *req, + struct request *next) +{ + /* + * if next expires before rq, assign its expire time to arq + * and move into next position (next will be deleted) in fifo + */ + if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) { + if (time_before(rq_fifo_time(next), rq_fifo_time(req))) { + list_move(&req->queuelist, &next->queuelist); + rq_set_fifo_time(req, rq_fifo_time(next)); + } + } + + /* + * kill knowledge of next, this one is a goner + */ + as_remove_queued_request(q, next); + as_put_io_context(next); + + RQ_SET_STATE(next, AS_RQ_MERGED); +} + +/* + * 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(struct work_struct *work) +{ + struct as_data *ad = container_of(work, struct as_data, antic_work); + struct request_queue *q = ad->q; + unsigned long flags; + + spin_lock_irqsave(q->queue_lock, flags); + blk_start_queueing(q); + spin_unlock_irqrestore(q->queue_lock, flags); +} + +static int as_may_queue(struct request_queue *q, int rw) +{ + int ret = ELV_MQUEUE_MAY; + struct as_data *ad = q->elevator->elevator_data; + struct io_context *ioc; + if (ad->antic_status == ANTIC_WAIT_REQ || + ad->antic_status == ANTIC_WAIT_NEXT) { + ioc = as_get_io_context(q->node); + if (ad->io_context == ioc) + ret = ELV_MQUEUE_MUST; + put_io_context(ioc); + } + + return ret; +} + +static void as_exit_queue(struct elevator_queue *e) +{ + struct as_data *ad = e->elevator_data; + + del_timer_sync(&ad->antic_timer); + cancel_work_sync(&ad->antic_work); + + BUG_ON(!list_empty(&ad->fifo_list[REQ_SYNC])); + BUG_ON(!list_empty(&ad->fifo_list[REQ_ASYNC])); + + put_io_context(ad->io_context); + kfree(ad); +} + +/* + * initialize elevator private data (as_data). + */ +static void *as_init_queue(struct request_queue *q) +{ + struct as_data *ad; + + ad = kmalloc_node(sizeof(*ad), GFP_KERNEL | __GFP_ZERO, q->node); + if (!ad) + return NULL; + + ad->q = q; /* Identify what queue the data belongs to */ + + /* 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); + + INIT_LIST_HEAD(&ad->fifo_list[REQ_SYNC]); + INIT_LIST_HEAD(&ad->fifo_list[REQ_ASYNC]); + ad->sort_list[REQ_SYNC] = RB_ROOT; + ad->sort_list[REQ_ASYNC] = RB_ROOT; + ad->fifo_expire[REQ_SYNC] = default_read_expire; + ad->fifo_expire[REQ_ASYNC] = default_write_expire; + ad->antic_expire = default_antic_expire; + ad->batch_expire[REQ_SYNC] = default_read_batch_expire; + ad->batch_expire[REQ_ASYNC] = default_write_batch_expire; + + ad->current_batch_expires = jiffies + ad->batch_expire[REQ_SYNC]; + ad->write_batch_count = ad->batch_expire[REQ_ASYNC] / 10; + if (ad->write_batch_count < 2) + ad->write_batch_count = 2; + + return ad; +} + +/* + * sysfs parts below + */ + +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; +} + +static ssize_t est_time_show(struct elevator_queue *e, char *page) +{ + struct as_data *ad = e->elevator_data; + int pos = 0; + + pos += sprintf(page+pos, "%lu %% exit probability\n", + 100*ad->exit_prob/256); + pos += sprintf(page+pos, "%lu %% probability of exiting without a " + "cooperating process submitting IO\n", + 100*ad->exit_no_coop/256); + pos += sprintf(page+pos, "%lu ms new thinktime\n", ad->new_ttime_mean); + pos += sprintf(page+pos, "%llu sectors new seek distance\n", + (unsigned long long)ad->new_seek_mean); + + return pos; +} + +#define SHOW_FUNCTION(__FUNC, __VAR) \ +static ssize_t __FUNC(struct elevator_queue *e, char *page) \ +{ \ + struct as_data *ad = e->elevator_data; \ + return as_var_show(jiffies_to_msecs((__VAR)), (page)); \ +} +SHOW_FUNCTION(as_read_expire_show, ad->fifo_expire[REQ_SYNC]); +SHOW_FUNCTION(as_write_expire_show, ad->fifo_expire[REQ_ASYNC]); +SHOW_FUNCTION(as_antic_expire_show, ad->antic_expire); +SHOW_FUNCTION(as_read_batch_expire_show, ad->batch_expire[REQ_SYNC]); +SHOW_FUNCTION(as_write_batch_expire_show, ad->batch_expire[REQ_ASYNC]); +#undef SHOW_FUNCTION + +#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \ +static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ +{ \ + struct as_data *ad = e->elevator_data; \ + int ret = as_var_store(__PTR, (page), count); \ + if (*(__PTR) < (MIN)) \ + *(__PTR) = (MIN); \ + else if (*(__PTR) > (MAX)) \ + *(__PTR) = (MAX); \ + *(__PTR) = msecs_to_jiffies(*(__PTR)); \ + return ret; \ +} +STORE_FUNCTION(as_read_expire_store, &ad->fifo_expire[REQ_SYNC], 0, INT_MAX); +STORE_FUNCTION(as_write_expire_store, &ad->fifo_expire[REQ_ASYNC], 0, INT_MAX); +STORE_FUNCTION(as_antic_expire_store, &ad->antic_expire, 0, INT_MAX); +STORE_FUNCTION(as_read_batch_expire_store, + &ad->batch_expire[REQ_SYNC], 0, INT_MAX); +STORE_FUNCTION(as_write_batch_expire_store, + &ad->batch_expire[REQ_ASYNC], 0, INT_MAX); +#undef STORE_FUNCTION + +#define AS_ATTR(name) \ + __ATTR(name, S_IRUGO|S_IWUSR, as_##name##_show, as_##name##_store) + +static struct elv_fs_entry as_attrs[] = { + __ATTR_RO(est_time), + AS_ATTR(read_expire), + AS_ATTR(write_expire), + AS_ATTR(antic_expire), + AS_ATTR(read_batch_expire), + AS_ATTR(write_batch_expire), + __ATTR_NULL +}; + +static struct elevator_type iosched_as = { + .ops = { + .elevator_merge_fn = as_merge, + .elevator_merged_fn = as_merged_request, + .elevator_merge_req_fn = as_merged_requests, + .elevator_dispatch_fn = as_dispatch_request, + .elevator_add_req_fn = as_add_request, + .elevator_activate_req_fn = as_activate_request, + .elevator_deactivate_req_fn = as_deactivate_request, + .elevator_queue_empty_fn = as_queue_empty, + .elevator_completed_req_fn = as_completed_request, + .elevator_former_req_fn = elv_rb_former_request, + .elevator_latter_req_fn = elv_rb_latter_request, + .elevator_may_queue_fn = as_may_queue, + .elevator_init_fn = as_init_queue, + .elevator_exit_fn = as_exit_queue, + .trim = as_trim, + }, + + .elevator_attrs = as_attrs, + .elevator_name = "anticipatory", + .elevator_owner = THIS_MODULE, +}; + +static int __init as_init(void) +{ + elv_register(&iosched_as); + + return 0; +} + +static void __exit as_exit(void) +{ + DECLARE_COMPLETION_ONSTACK(all_gone); + elv_unregister(&iosched_as); + ioc_gone = &all_gone; + /* ioc_gone's update must be visible before reading ioc_count */ + smp_wmb(); + if (elv_ioc_count_read(ioc_count)) + wait_for_completion(&all_gone); + synchronize_rcu(); +} + +module_init(as_init); +module_exit(as_exit); + +MODULE_AUTHOR("Nick Piggin"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("anticipatory IO scheduler"); |