* Anticipatory & deadline i/o scheduler.
*
* Copyright (C) 2002 Jens Axboe <axboe@suse.de>
- * Nick Piggin <piggin@cyberone.com.au>
+ * Nick Piggin <nickpiggin@yahoo.com.au>
*
*/
#include <linux/kernel.h>
/* Bits in as_io_context.state */
enum as_io_states {
- AS_TASK_RUNNING=0, /* Process has not exitted */
+ AS_TASK_RUNNING=0, /* Process has not exited */
AS_TASK_IOSTARTED, /* Process has started some IO */
AS_TASK_IORUNNING, /* Process has completed some IO */
};
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 */
kblockd_schedule_work(&ad->antic_work);
if (aic->ttime_samples == 0) {
- /* process anticipated on has exitted or timed out*/
+ /* 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_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)
+{
+ struct as_rq *arq = RQ_DATA(rq);
+ int data_dir = arq->is_sync;
+ 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_rq *arq)
+static int as_close_req(struct as_data *ad, struct as_io_context *aic,
+ 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) */
+ sector_t s;
if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished)
delay = 0;
else
delay = ((jiffies - ad->antic_start) * 1000) / HZ;
- if (delay <= 1)
- delta = 64;
+ if (delay == 0)
+ delta = 8192;
else if (delay <= 20 && delay <= ad->antic_expire)
- delta = 64 << (delay-1);
+ delta = 8192 << delay;
else
return 1;
- return (last - (delta>>1) <= next) && (next <= last + delta);
+ 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;
}
/*
* 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 the task which has submitted the request has exited, break anticipation.
*
* If this task has queued some other IO, do not enter enticipation.
*/
{
struct io_context *ioc;
struct as_io_context *aic;
- sector_t s;
ioc = ad->io_context;
BUG_ON(!ioc);
if (!aic)
return 0;
- if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
- /* process anticipated on has exitted */
- if (aic->ttime_samples == 0)
- ad->exit_prob = (7*ad->exit_prob + 256)/8;
- return 1;
- }
-
if (atomic_read(&aic->nr_queued) > 0) {
/* process has more requests queued */
return 1;
return 1;
}
- if (arq && arq->is_sync == REQ_SYNC && as_close_req(ad, arq)) {
+ if (arq && arq->is_sync == REQ_SYNC && as_close_req(ad, aic, arq)) {
/*
* Found a close request that is not one of ours.
*
- * This makes close requests from another process reset
- * our thinktime delay. Is generally useful when there are
+ * 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.
*/
- spin_lock(&aic->lock);
- aic->last_end_request = jiffies;
- spin_unlock(&aic->lock);
+ 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, arq->request);
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)
+ return 1;
+ }
if (aic->ttime_samples == 0) {
if (ad->new_ttime_mean > ad->antic_expire)
return 1;
- if (ad->exit_prob > 128)
+ if (ad->exit_prob * ad->exit_no_coop > 128*256)
return 1;
} else if (aic->ttime_mean > ad->antic_expire) {
/* the process thinks too much between requests */
return 1;
}
- if (!arq)
- return 0;
-
- if (ad->last_sector[REQ_SYNC] < arq->request->sector)
- s = arq->request->sector - ad->last_sector[REQ_SYNC];
- else
- s = ad->last_sector[REQ_SYNC] - arq->request->sector;
-
- if (aic->seek_samples == 0) {
- /*
- * Process has just started IO. Use past statistics to
- * guage 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;
}
* 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;
}
-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)
-{
- struct as_rq *arq = RQ_DATA(rq);
- int data_dir = arq->is_sync;
- unsigned long thinktime;
- 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);
- } else
- thinktime = 0;
- 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_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
|| ad->changed_batch)
return 0;
- if (!(reads && writes && as_batch_expired(ad)) ) {
+ if (!(reads && writes && as_batch_expired(ad))) {
/*
* batch is still running or no reads or no writes
*/
* Add arq to a list behind alias
*/
static inline void
-as_add_aliased_request(struct as_data *ad, struct as_rq *arq, struct as_rq *alias)
+as_add_aliased_request(struct as_data *ad, struct as_rq *arq,
+ struct as_rq *alias)
{
struct request *req = arq->request;
struct list_head *insert = alias->request->queuelist.prev;
&& list_empty(&ad->fifo_list[REQ_SYNC]);
}
-static struct request *
-as_former_request(request_queue_t *q, struct request *rq)
+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);
return ret;
}
-static struct request *
-as_latter_request(request_queue_t *q, struct request *rq)
+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);
* currently don't bother. Ditto the next function.
*/
as_del_arq_rb(ad, arq);
- if ((alias = as_add_arq_rb(ad, arq)) ) {
+ if ((alias = as_add_arq_rb(ad, arq))) {
list_del_init(&arq->fifo);
as_add_aliased_request(ad, arq, alias);
if (next_arq)
}
}
-static void
-as_merged_requests(request_queue_t *q, struct request *req,
- struct request *next)
+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);
next_arq = as_find_next_arq(ad, arq);
as_del_arq_rb(ad, arq);
- if ((alias = as_add_arq_rb(ad, arq)) ) {
+ if ((alias = as_add_arq_rb(ad, arq))) {
list_del_init(&arq->fifo);
as_add_aliased_request(ad, arq, alias);
if (next_arq)
{
int pos = 0;
- pos += sprintf(page+pos, "%lu %% exit probability\n", 100*ad->exit_prob/256);
+ 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);
+ pos += sprintf(page+pos, "%llu sectors new seek distance\n",
+ (unsigned long long)ad->new_seek_mean);
return pos;
}
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