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WSL2-Linux-Kernel/block/as-iosched.c

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/*
* Anticipatory & deadline i/o scheduler.
*
* Copyright (C) 2002 Jens Axboe <axboe@suse.de>
* 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/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>
#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 as_rq *next_arq[2]; /* next in sort order */
sector_t last_sector[2]; /* last REQ_SYNC & REQ_ASYNC sectors */
struct list_head *hash; /* request hash */
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? */
mempool_t *arq_pool;
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;
};
#define list_entry_fifo(ptr) list_entry((ptr), struct as_rq, fifo)
/*
* 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 */
};
struct as_rq {
/*
* rbtree index, key is the starting offset
*/
struct rb_node rb_node;
sector_t rb_key;
struct request *request;
struct io_context *io_context; /* The submitting task */
/*
* request hash, key is the ending offset (for back merge lookup)
*/
struct list_head hash;
unsigned int on_hash;
/*
* expire fifo
*/
struct list_head fifo;
unsigned long expires;
unsigned int is_sync;
enum arq_state state;
};
#define RQ_DATA(rq) ((struct as_rq *) (rq)->elevator_private)
static kmem_cache_t *arq_pool;
static atomic_t ioc_count = ATOMIC_INIT(0);
static struct completion *ioc_gone;
static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq);
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);
if (atomic_dec_and_test(&ioc_count) && ioc_gone)
complete(ioc_gone);
}
static void as_trim(struct io_context *ioc)
{
if (ioc->aic)
free_as_io_context(ioc->aic);
ioc->aic = NULL;
}
/* 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;
atomic_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(void)
{
struct io_context *ioc = get_io_context(GFP_ATOMIC);
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 as_rq *arq)
{
struct as_io_context *aic;
if (unlikely(!arq->io_context))
return;
aic = arq->io_context->aic;
if (arq->is_sync == REQ_SYNC && aic) {
spin_lock(&aic->lock);
set_bit(AS_TASK_IORUNNING, &aic->state);
aic->last_end_request = jiffies;
spin_unlock(&aic->lock);
}
put_io_context(arq->io_context);
}
/*
* the back merge hash support functions
*/
static const int as_hash_shift = 6;
#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)
static inline void __as_del_arq_hash(struct as_rq *arq)
{
arq->on_hash = 0;
list_del_init(&arq->hash);
}
static inline void as_del_arq_hash(struct as_rq *arq)
{
if (arq->on_hash)
__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(arq->on_hash);
arq->on_hash = 1;
list_add(&arq->hash, &ad->hash[AS_HASH_FN(rq_hash_key(rq))]);
}
/*
* move hot entry to front of chain
*/
static inline void as_hot_arq_hash(struct as_data *ad, struct as_rq *arq)
{
struct request *rq = arq->request;
struct list_head *head = &ad->hash[AS_HASH_FN(rq_hash_key(rq))];
if (!arq->on_hash) {
WARN_ON(1);
return;
}
if (arq->hash.prev != head) {
list_del(&arq->hash);
list_add(&arq->hash, head);
}
}
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(!arq->on_hash);
if (!rq_mergeable(__rq)) {
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[(arq)->is_sync])
#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;
}
}
/*
* Add 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 return the alias.
*/
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;
struct request *rq = arq->request;
arq->rb_key = rq_rb_key(rq);
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);
rb_insert_color(&arq->rb_node, ARQ_RB_ROOT(ad, arq));
return NULL;
}
static void as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
{
struct as_rq *alias;
while ((unlikely(alias = __as_add_arq_rb(ad, arq)))) {
as_move_to_dispatch(ad, alias);
as_antic_stop(ad);
}
}
static inline void as_del_arq_rb(struct as_data *ad, struct as_rq *arq)
{
if (!ON_RB(&arq->rb_node)) {
WARN_ON(1);
return;
}
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 (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 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 = arq1->is_sync;
last = ad->last_sector[data_dir];
s1 = arq1->request->sector;
s2 = arq2->request->sector;
BUG_ON(data_dir != arq2->is_sync);
/*
* 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 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_req 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 = last->is_sync;
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;
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->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 = ad->io_context->aic;
ad->antic_status = ANTIC_FINISHED;
kblockd_schedule_work(&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_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_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 == 0)
delta = 8192;
else if (delay <= 20 && 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 as_rq *arq)
{
struct io_context *ioc;
struct as_io_context *aic;
ioc = ad->io_context;
BUG_ON(!ioc);
if (arq && ioc == arq->io_context) {
/* request from same process */
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.
*/
return 1;
}
aic = ioc->aic;
if (!aic)
return 0;
if (atomic_read(&aic->nr_queued) > 0) {
/* process has more requests queued */
return 1;
}
if (atomic_read(&aic->nr_dispatched) > 0) {
/* process has more requests dispatched */
return 1;
}
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 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, 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 * 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;
}
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->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, 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_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 = arq->is_sync;
/* 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->antic_status == ANTIC_WAIT_REQ
|| ad->antic_status == ANTIC_WAIT_NEXT) {
if (as_can_break_anticipation(ad, arq))
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(request_queue_t *q, struct request *rq)
{
struct as_data *ad = q->elevator->elevator_data;
struct as_rq *arq = RQ_DATA(rq);
WARN_ON(!list_empty(&rq->queuelist));
if (arq->state != AS_RQ_REMOVED) {
printk("arq->state %d\n", arq->state);
WARN_ON(1);
goto out;
}
if (ad->changed_batch && ad->nr_dispatched == 1) {
kblockd_schedule_work(&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 == arq->is_sync) {
update_write_batch(ad);
ad->current_batch_expires = jiffies +
ad->batch_expire[REQ_SYNC];
ad->new_batch = 0;
}
if (ad->io_context == arq->io_context && 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(arq);
out:
arq->state = 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(request_queue_t *q, struct request *rq)
{
struct as_rq *arq = RQ_DATA(rq);
const int data_dir = arq->is_sync;
struct as_data *ad = q->elevator->elevator_data;
WARN_ON(arq->state != AS_RQ_QUEUED);
if (arq->io_context && arq->io_context->aic) {
BUG_ON(!atomic_read(&arq->io_context->aic->nr_queued));
atomic_dec(&arq->io_context->aic->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);
}
/*
* 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)
{
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 as_rq *arq)
{
struct request *rq = arq->request;
const int data_dir = arq->is_sync;
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] = rq->sector + rq->nr_sectors;
if (data_dir == REQ_SYNC) {
/* In case we have to anticipate after this */
copy_io_context(&ad->io_context, &arq->io_context);
} 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_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, rq);
WARN_ON(arq->state != AS_RQ_QUEUED);
elv_dispatch_sort(ad->q, rq);
arq->state = AS_RQ_DISPATCHED;
if (arq->io_context && arq->io_context->aic)
atomic_inc(&arq->io_context->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(request_queue_t *q, int force)
{
struct as_data *ad = q->elevator->elevator_data;
struct as_rq *arq;
const int reads = !list_empty(&ad->fifo_list[REQ_SYNC]);
const int writes = !list_empty(&ad->fifo_list[REQ_ASYNC]);
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_arq[REQ_SYNC]) {
as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]);
dispatched++;
}
ad->last_check_fifo[REQ_SYNC] = jiffies;
while (ad->next_arq[REQ_ASYNC]) {
as_move_to_dispatch(ad, ad->next_arq[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
*/
arq = ad->next_arq[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, 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[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(&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;
arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].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(&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;
arq = ad->next_arq[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:
arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next);
BUG_ON(arq == NULL);
}
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;
}
/*
* arq is the selected appropriate request.
*/
as_move_to_dispatch(ad, arq);
return 1;
}
/*
* add arq to rbtree and fifo
*/
static void as_add_request(request_queue_t *q, struct request *rq)
{
struct as_data *ad = q->elevator->elevator_data;
struct as_rq *arq = RQ_DATA(rq);
int data_dir;
arq->state = AS_RQ_NEW;
if (rq_data_dir(arq->request) == READ
|| current->flags&PF_SYNCWRITE)
arq->is_sync = 1;
else
arq->is_sync = 0;
data_dir = arq->is_sync;
arq->io_context = as_get_io_context();
if (arq->io_context) {
as_update_iohist(ad, arq->io_context->aic, arq->request);
atomic_inc(&arq->io_context->aic->nr_queued);
}
as_add_arq_rb(ad, arq);
if (rq_mergeable(arq->request))
as_add_arq_hash(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]);
as_update_arq(ad, arq); /* keep state machine up to date */
arq->state = AS_RQ_QUEUED;
}
static void as_activate_request(request_queue_t *q, struct request *rq)
{
struct as_rq *arq = RQ_DATA(rq);
WARN_ON(arq->state != AS_RQ_DISPATCHED);
arq->state = AS_RQ_REMOVED;
if (arq->io_context && arq->io_context->aic)
atomic_dec(&arq->io_context->aic->nr_dispatched);
}
static void as_deactivate_request(request_queue_t *q, struct request *rq)
{
struct as_rq *arq = RQ_DATA(rq);
WARN_ON(arq->state != AS_RQ_REMOVED);
arq->state = AS_RQ_DISPATCHED;
if (arq->io_context && arq->io_context->aic)
atomic_inc(&arq->io_context->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(request_queue_t *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 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 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;
int ret;
/*
* 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
*/
__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:
if (ret) {
if (rq_mergeable(__rq))
as_hot_arq_hash(ad, RQ_DATA(__rq));
}
*req = __rq;
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.
*/
}
}
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_io_context(&arq->io_context, &anext->io_context);
}
}
/*
* kill knowledge of next, this one is a goner
*/
as_remove_queued_request(q, next);
as_put_io_context(anext);
anext->state = 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(void *data)
{
struct request_queue *q = data;
unsigned long flags;
spin_lock_irqsave(q->queue_lock, flags);
if (!as_queue_empty(q))
q->request_fn(q);
spin_unlock_irqrestore(q->queue_lock, flags);
}
static void as_put_request(request_queue_t *q, struct request *rq)
{
struct as_data *ad = q->elevator->elevator_data;
struct as_rq *arq = RQ_DATA(rq);
if (!arq) {
WARN_ON(1);
return;
}
if (unlikely(arq->state != AS_RQ_POSTSCHED &&
arq->state != AS_RQ_PRESCHED &&
arq->state != AS_RQ_MERGED)) {
printk("arq->state %d\n", arq->state);
WARN_ON(1);
}
mempool_free(arq, ad->arq_pool);
rq->elevator_private = NULL;
}
static int as_set_request(request_queue_t *q, struct request *rq,
struct bio *bio, gfp_t gfp_mask)
{
struct as_data *ad = q->elevator->elevator_data;
struct as_rq *arq = mempool_alloc(ad->arq_pool, gfp_mask);
if (arq) {
memset(arq, 0, sizeof(*arq));
RB_CLEAR(&arq->rb_node);
arq->request = rq;
arq->state = AS_RQ_PRESCHED;
arq->io_context = NULL;
INIT_LIST_HEAD(&arq->hash);
arq->on_hash = 0;
INIT_LIST_HEAD(&arq->fifo);
rq->elevator_private = arq;
return 0;
}
return 1;
}
static int as_may_queue(request_queue_t *q, int rw, struct bio *bio)
{
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();
if (ad->io_context == ioc)
ret = ELV_MQUEUE_MUST;
put_io_context(ioc);
}
return ret;
}
static void as_exit_queue(elevator_t *e)
{
struct as_data *ad = e->elevator_data;
del_timer_sync(&ad->antic_timer);
kblockd_flush();
BUG_ON(!list_empty(&ad->fifo_list[REQ_SYNC]));
BUG_ON(!list_empty(&ad->fifo_list[REQ_ASYNC]));
mempool_destroy(ad->arq_pool);
put_io_context(ad->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 void *as_init_queue(request_queue_t *q, elevator_t *e)
{
struct as_data *ad;
int i;
if (!arq_pool)
return NULL;
ad = kmalloc_node(sizeof(*ad), GFP_KERNEL, q->node);
if (!ad)
return NULL;
memset(ad, 0, sizeof(*ad));
ad->q = q; /* Identify what queue the data belongs to */
ad->hash = kmalloc_node(sizeof(struct list_head)*AS_HASH_ENTRIES,
GFP_KERNEL, q->node);
if (!ad->hash) {
kfree(ad);
return NULL;
}
ad->arq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
mempool_free_slab, arq_pool, q->node);
if (!ad->arq_pool) {
kfree(ad->hash);
kfree(ad);
return NULL;
}
/* 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[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(elevator_t *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(elevator_t *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(elevator_t *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 = as_former_request,
.elevator_latter_req_fn = as_latter_request,
.elevator_set_req_fn = as_set_request,
.elevator_put_req_fn = as_put_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)
{
int ret;
arq_pool = kmem_cache_create("as_arq", sizeof(struct as_rq),
0, 0, NULL, NULL);
if (!arq_pool)
return -ENOMEM;
ret = elv_register(&iosched_as);
if (!ret) {
/*
* don't allow AS to get unregistered, since we would have
* to browse all tasks in the system and release their
* as_io_context first
*/
__module_get(THIS_MODULE);
return 0;
}
kmem_cache_destroy(arq_pool);
return ret;
}
static void __exit as_exit(void)
{
DECLARE_COMPLETION(all_gone);
elv_unregister(&iosched_as);
ioc_gone = &all_gone;
/* ioc_gone's update must be visible before reading ioc_count */
smp_wmb();
if (atomic_read(&ioc_count))
wait_for_completion(ioc_gone);
synchronize_rcu();
kmem_cache_destroy(arq_pool);
}
module_init(as_init);
module_exit(as_exit);
MODULE_AUTHOR("Nick Piggin");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("anticipatory IO scheduler");
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