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cfq-iosched.c
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cfq-iosched.c
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/*
* CFQ, or complete fairness queueing, disk scheduler.
*
* Based on ideas from a previously unfinished io
* scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
*
* Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/elevator.h>
#include <linux/jiffies.h>
#include <linux/rbtree.h>
#include <linux/ioprio.h>
#include <linux/blktrace_api.h>
#include "blk.h"
#include "cfq.h"
/*
* tunables
*/
/* max queue in one round of service */
static const int cfq_quantum = 8;
static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
/* maximum backwards seek, in KiB */
static const int cfq_back_max = 16 * 1024;
/* penalty of a backwards seek */
static const int cfq_back_penalty = 2;
static const int cfq_slice_sync = HZ / 10;
static int cfq_slice_async = HZ / 25;
static const int cfq_slice_async_rq = 2;
static int cfq_slice_idle = HZ / 125;
static int cfq_group_idle = HZ / 125;
static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
static const int cfq_hist_divisor = 4;
/*
* offset from end of service tree
*/
#define CFQ_IDLE_DELAY (HZ / 5)
/*
* below this threshold, we consider thinktime immediate
*/
#define CFQ_MIN_TT (2)
#define CFQ_SLICE_SCALE (5)
#define CFQ_HW_QUEUE_MIN (5)
#define CFQ_SERVICE_SHIFT 12
#define CFQQ_SEEK_THR (sector_t)(8 * 100)
#define CFQQ_CLOSE_THR (sector_t)(8 * 1024)
#define CFQQ_SECT_THR_NONROT (sector_t)(2 * 32)
#define CFQQ_SEEKY(cfqq) (hweight32(cfqq->seek_history) > 32/8)
#define RQ_CIC(rq) icq_to_cic((rq)->elv.icq)
#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elv.priv[0])
#define RQ_CFQG(rq) (struct cfq_group *) ((rq)->elv.priv[1])
static struct kmem_cache *cfq_pool;
#define CFQ_PRIO_LISTS IOPRIO_BE_NR
#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
#define sample_valid(samples) ((samples) > 80)
#define rb_entry_cfqg(node) rb_entry((node), struct cfq_group, rb_node)
struct cfq_ttime {
unsigned long last_end_request;
unsigned long ttime_total;
unsigned long ttime_samples;
unsigned long ttime_mean;
};
/*
* Most of our rbtree usage is for sorting with min extraction, so
* if we cache the leftmost node we don't have to walk down the tree
* to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
* move this into the elevator for the rq sorting as well.
*/
struct cfq_rb_root {
struct rb_root rb;
struct rb_node *left;
unsigned count;
unsigned total_weight;
u64 min_vdisktime;
struct cfq_ttime ttime;
};
#define CFQ_RB_ROOT (struct cfq_rb_root) { .rb = RB_ROOT, \
.ttime = {.last_end_request = jiffies,},}
/*
* Per process-grouping structure
*/
struct cfq_queue {
/* reference count */
int ref;
/* various state flags, see below */
unsigned int flags;
/* parent cfq_data */
struct cfq_data *cfqd;
/* service_tree member */
struct rb_node rb_node;
/* service_tree key */
unsigned long rb_key;
/* prio tree member */
struct rb_node p_node;
/* prio tree root we belong to, if any */
struct rb_root *p_root;
/* sorted list of pending requests */
struct rb_root sort_list;
/* if fifo isn't expired, next request to serve */
struct request *next_rq;
/* requests queued in sort_list */
int queued[2];
/* currently allocated requests */
int allocated[2];
/* fifo list of requests in sort_list */
struct list_head fifo;
/* time when queue got scheduled in to dispatch first request. */
unsigned long dispatch_start;
unsigned int allocated_slice;
unsigned int slice_dispatch;
/* time when first request from queue completed and slice started. */
unsigned long slice_start;
unsigned long slice_end;
long slice_resid;
/* pending priority requests */
int prio_pending;
/* number of requests that are on the dispatch list or inside driver */
int dispatched;
/* io prio of this group */
unsigned short ioprio, org_ioprio;
unsigned short ioprio_class;
pid_t pid;
u32 seek_history;
sector_t last_request_pos;
struct cfq_rb_root *service_tree;
struct cfq_queue *new_cfqq;
struct cfq_group *cfqg;
/* Number of sectors dispatched from queue in single dispatch round */
unsigned long nr_sectors;
};
/*
* First index in the service_trees.
* IDLE is handled separately, so it has negative index
*/
enum wl_prio_t {
BE_WORKLOAD = 0,
RT_WORKLOAD = 1,
IDLE_WORKLOAD = 2,
CFQ_PRIO_NR,
};
/*
* Second index in the service_trees.
*/
enum wl_type_t {
ASYNC_WORKLOAD = 0,
SYNC_NOIDLE_WORKLOAD = 1,
SYNC_WORKLOAD = 2
};
/* This is per cgroup per device grouping structure */
struct cfq_group {
/* group service_tree member */
struct rb_node rb_node;
/* group service_tree key */
u64 vdisktime;
unsigned int weight;
unsigned int new_weight;
bool needs_update;
/* number of cfqq currently on this group */
int nr_cfqq;
/*
* Per group busy queues average. Useful for workload slice calc. We
* create the array for each prio class but at run time it is used
* only for RT and BE class and slot for IDLE class remains unused.
* This is primarily done to avoid confusion and a gcc warning.
*/
unsigned int busy_queues_avg[CFQ_PRIO_NR];
/*
* rr lists of queues with requests. We maintain service trees for
* RT and BE classes. These trees are subdivided in subclasses
* of SYNC, SYNC_NOIDLE and ASYNC based on workload type. For IDLE
* class there is no subclassification and all the cfq queues go on
* a single tree service_tree_idle.
* Counts are embedded in the cfq_rb_root
*/
struct cfq_rb_root service_trees[2][3];
struct cfq_rb_root service_tree_idle;
unsigned long saved_workload_slice;
enum wl_type_t saved_workload;
enum wl_prio_t saved_serving_prio;
struct blkio_group blkg;
#ifdef CONFIG_CFQ_GROUP_IOSCHED
struct hlist_node cfqd_node;
int ref;
#endif
/* number of requests that are on the dispatch list or inside driver */
int dispatched;
struct cfq_ttime ttime;
};
struct cfq_io_cq {
struct io_cq icq; /* must be the first member */
struct cfq_queue *cfqq[2];
struct cfq_ttime ttime;
};
/*
* Per block device queue structure
*/
struct cfq_data {
struct request_queue *queue;
/* Root service tree for cfq_groups */
struct cfq_rb_root grp_service_tree;
struct cfq_group root_group;
/*
* The priority currently being served
*/
enum wl_prio_t serving_prio;
enum wl_type_t serving_type;
unsigned long workload_expires;
struct cfq_group *serving_group;
/*
* Each priority tree is sorted by next_request position. These
* trees are used when determining if two or more queues are
* interleaving requests (see cfq_close_cooperator).
*/
struct rb_root prio_trees[CFQ_PRIO_LISTS];
unsigned int busy_queues;
unsigned int busy_sync_queues;
int rq_in_driver;
int rq_in_flight[2];
/*
* queue-depth detection
*/
int rq_queued;
int hw_tag;
/*
* hw_tag can be
* -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
* 1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
* 0 => no NCQ
*/
int hw_tag_est_depth;
unsigned int hw_tag_samples;
/*
* idle window management
*/
struct timer_list idle_slice_timer;
struct work_struct unplug_work;
struct cfq_queue *active_queue;
struct cfq_io_cq *active_cic;
/*
* async queue for each priority case
*/
struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
struct cfq_queue *async_idle_cfqq;
sector_t last_position;
/*
* tunables, see top of file
*/
unsigned int cfq_quantum;
unsigned int cfq_fifo_expire[2];
unsigned int cfq_back_penalty;
unsigned int cfq_back_max;
unsigned int cfq_slice[2];
unsigned int cfq_slice_async_rq;
unsigned int cfq_slice_idle;
unsigned int cfq_group_idle;
unsigned int cfq_latency;
unsigned int cfq_target_latency;
/*
* Fallback dummy cfqq for extreme OOM conditions
*/
struct cfq_queue oom_cfqq;
unsigned long last_delayed_sync;
/* List of cfq groups being managed on this device*/
struct hlist_head cfqg_list;
/* Number of groups which are on blkcg->blkg_list */
unsigned int nr_blkcg_linked_grps;
};
static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
enum wl_prio_t prio,
enum wl_type_t type)
{
if (!cfqg)
return NULL;
if (prio == IDLE_WORKLOAD)
return &cfqg->service_tree_idle;
return &cfqg->service_trees[prio][type];
}
enum cfqq_state_flags {
CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */
CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
CFQ_CFQQ_FLAG_sync, /* synchronous queue */
CFQ_CFQQ_FLAG_coop, /* cfqq is shared */
CFQ_CFQQ_FLAG_split_coop, /* shared cfqq will be splitted */
CFQ_CFQQ_FLAG_deep, /* sync cfqq experienced large depth */
CFQ_CFQQ_FLAG_wait_busy, /* Waiting for next request */
};
#define CFQ_CFQQ_FNS(name) \
static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
{ \
(cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
} \
static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
{ \
(cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
} \
static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
{ \
return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
}
CFQ_CFQQ_FNS(on_rr);
CFQ_CFQQ_FNS(wait_request);
CFQ_CFQQ_FNS(must_dispatch);
CFQ_CFQQ_FNS(must_alloc_slice);
CFQ_CFQQ_FNS(fifo_expire);
CFQ_CFQQ_FNS(idle_window);
CFQ_CFQQ_FNS(prio_changed);
CFQ_CFQQ_FNS(slice_new);
CFQ_CFQQ_FNS(sync);
CFQ_CFQQ_FNS(coop);
CFQ_CFQQ_FNS(split_coop);
CFQ_CFQQ_FNS(deep);
CFQ_CFQQ_FNS(wait_busy);
#undef CFQ_CFQQ_FNS
#ifdef CONFIG_CFQ_GROUP_IOSCHED
#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
blkg_path(&(cfqq)->cfqg->blkg), ##args)
#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) \
blk_add_trace_msg((cfqd)->queue, "%s " fmt, \
blkg_path(&(cfqg)->blkg), ##args) \
#else
#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) do {} while (0)
#endif
#define cfq_log(cfqd, fmt, args...) \
blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
/* Traverses through cfq group service trees */
#define for_each_cfqg_st(cfqg, i, j, st) \
for (i = 0; i <= IDLE_WORKLOAD; i++) \
for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
: &cfqg->service_tree_idle; \
(i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
(i == IDLE_WORKLOAD && j == 0); \
j++, st = i < IDLE_WORKLOAD ? \
&cfqg->service_trees[i][j]: NULL) \
static inline bool cfq_io_thinktime_big(struct cfq_data *cfqd,
struct cfq_ttime *ttime, bool group_idle)
{
unsigned long slice;
if (!sample_valid(ttime->ttime_samples))
return false;
if (group_idle)
slice = cfqd->cfq_group_idle;
else
slice = cfqd->cfq_slice_idle;
return ttime->ttime_mean > slice;
}
static inline bool iops_mode(struct cfq_data *cfqd)
{
/*
* If we are not idling on queues and it is a NCQ drive, parallel
* execution of requests is on and measuring time is not possible
* in most of the cases until and unless we drive shallower queue
* depths and that becomes a performance bottleneck. In such cases
* switch to start providing fairness in terms of number of IOs.
*/
if (!cfqd->cfq_slice_idle && cfqd->hw_tag)
return true;
else
return false;
}
static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
{
if (cfq_class_idle(cfqq))
return IDLE_WORKLOAD;
if (cfq_class_rt(cfqq))
return RT_WORKLOAD;
return BE_WORKLOAD;
}
static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
{
if (!cfq_cfqq_sync(cfqq))
return ASYNC_WORKLOAD;
if (!cfq_cfqq_idle_window(cfqq))
return SYNC_NOIDLE_WORKLOAD;
return SYNC_WORKLOAD;
}
static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
struct cfq_data *cfqd,
struct cfq_group *cfqg)
{
if (wl == IDLE_WORKLOAD)
return cfqg->service_tree_idle.count;
return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
+ cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
+ cfqg->service_trees[wl][SYNC_WORKLOAD].count;
}
static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
struct cfq_group *cfqg)
{
return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count
+ cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
}
static void cfq_dispatch_insert(struct request_queue *, struct request *);
static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
struct io_context *, gfp_t);
static inline struct cfq_io_cq *icq_to_cic(struct io_cq *icq)
{
/* cic->icq is the first member, %NULL will convert to %NULL */
return container_of(icq, struct cfq_io_cq, icq);
}
static inline struct cfq_io_cq *cfq_cic_lookup(struct cfq_data *cfqd,
struct io_context *ioc)
{
if (ioc)
return icq_to_cic(ioc_lookup_icq(ioc, cfqd->queue));
return NULL;
}
static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_cq *cic, bool is_sync)
{
return cic->cfqq[is_sync];
}
static inline void cic_set_cfqq(struct cfq_io_cq *cic, struct cfq_queue *cfqq,
bool is_sync)
{
cic->cfqq[is_sync] = cfqq;
}
static inline struct cfq_data *cic_to_cfqd(struct cfq_io_cq *cic)
{
return cic->icq.q->elevator->elevator_data;
}
/*
* We regard a request as SYNC, if it's either a read or has the SYNC bit
* set (in which case it could also be direct WRITE).
*/
static inline bool cfq_bio_sync(struct bio *bio)
{
return bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC);
}
/*
* scheduler run of queue, if there are requests pending and no one in the
* driver that will restart queueing
*/
static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
{
if (cfqd->busy_queues) {
cfq_log(cfqd, "schedule dispatch");
kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
}
}
/*
* Scale schedule slice based on io priority. Use the sync time slice only
* if a queue is marked sync and has sync io queued. A sync queue with async
* io only, should not get full sync slice length.
*/
static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
unsigned short prio)
{
const int base_slice = cfqd->cfq_slice[sync];
WARN_ON(prio >= IOPRIO_BE_NR);
return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
}
static inline int
cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
}
static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
{
u64 d = delta << CFQ_SERVICE_SHIFT;
d = d * BLKIO_WEIGHT_DEFAULT;
do_div(d, cfqg->weight);
return d;
}
static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
{
s64 delta = (s64)(vdisktime - min_vdisktime);
if (delta > 0)
min_vdisktime = vdisktime;
return min_vdisktime;
}
static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
{
s64 delta = (s64)(vdisktime - min_vdisktime);
if (delta < 0)
min_vdisktime = vdisktime;
return min_vdisktime;
}
static void update_min_vdisktime(struct cfq_rb_root *st)
{
struct cfq_group *cfqg;
if (st->left) {
cfqg = rb_entry_cfqg(st->left);
st->min_vdisktime = max_vdisktime(st->min_vdisktime,
cfqg->vdisktime);
}
}
/*
* get averaged number of queues of RT/BE priority.
* average is updated, with a formula that gives more weight to higher numbers,
* to quickly follows sudden increases and decrease slowly
*/
static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
struct cfq_group *cfqg, bool rt)
{
unsigned min_q, max_q;
unsigned mult = cfq_hist_divisor - 1;
unsigned round = cfq_hist_divisor / 2;
unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
min_q = min(cfqg->busy_queues_avg[rt], busy);
max_q = max(cfqg->busy_queues_avg[rt], busy);
cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
cfq_hist_divisor;
return cfqg->busy_queues_avg[rt];
}
static inline unsigned
cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
struct cfq_rb_root *st = &cfqd->grp_service_tree;
return cfqd->cfq_target_latency * cfqg->weight / st->total_weight;
}
static inline unsigned
cfq_scaled_cfqq_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
if (cfqd->cfq_latency) {
/*
* interested queues (we consider only the ones with the same
* priority class in the cfq group)
*/
unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
cfq_class_rt(cfqq));
unsigned sync_slice = cfqd->cfq_slice[1];
unsigned expect_latency = sync_slice * iq;
unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
if (expect_latency > group_slice) {
unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
/* scale low_slice according to IO priority
* and sync vs async */
unsigned low_slice =
min(slice, base_low_slice * slice / sync_slice);
/* the adapted slice value is scaled to fit all iqs
* into the target latency */
slice = max(slice * group_slice / expect_latency,
low_slice);
}
}
return slice;
}
static inline void
cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
unsigned slice = cfq_scaled_cfqq_slice(cfqd, cfqq);
cfqq->slice_start = jiffies;
cfqq->slice_end = jiffies + slice;
cfqq->allocated_slice = slice;
cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
}
/*
* We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
* isn't valid until the first request from the dispatch is activated
* and the slice time set.
*/
static inline bool cfq_slice_used(struct cfq_queue *cfqq)
{
if (cfq_cfqq_slice_new(cfqq))
return false;
if (time_before(jiffies, cfqq->slice_end))
return false;
return true;
}
/*
* Lifted from AS - choose which of rq1 and rq2 that is best served now.
* We choose the request that is closest to the head right now. Distance
* behind the head is penalized and only allowed to a certain extent.
*/
static struct request *
cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
{
sector_t s1, s2, d1 = 0, d2 = 0;
unsigned long back_max;
#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
unsigned wrap = 0; /* bit mask: requests behind the disk head? */
if (rq1 == NULL || rq1 == rq2)
return rq2;
if (rq2 == NULL)
return rq1;
if (rq_is_sync(rq1) != rq_is_sync(rq2))
return rq_is_sync(rq1) ? rq1 : rq2;
if ((rq1->cmd_flags ^ rq2->cmd_flags) & REQ_PRIO)
return rq1->cmd_flags & REQ_PRIO ? rq1 : rq2;
s1 = blk_rq_pos(rq1);
s2 = blk_rq_pos(rq2);
/*
* by definition, 1KiB is 2 sectors
*/
back_max = cfqd->cfq_back_max * 2;
/*
* 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 + back_max >= last)
d1 = (last - s1) * cfqd->cfq_back_penalty;
else
wrap |= CFQ_RQ1_WRAP;
if (s2 >= last)
d2 = s2 - last;
else if (s2 + back_max >= last)
d2 = (last - s2) * cfqd->cfq_back_penalty;
else
wrap |= CFQ_RQ2_WRAP;
/* Found required data */
/*
* By doing switch() on the bit mask "wrap" we avoid having to
* check two variables for all permutations: --> faster!
*/
switch (wrap) {
case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
if (d1 < d2)
return rq1;
else if (d2 < d1)
return rq2;
else {
if (s1 >= s2)
return rq1;
else
return rq2;
}
case CFQ_RQ2_WRAP:
return rq1;
case CFQ_RQ1_WRAP:
return rq2;
case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
default:
/*
* Since both rqs are wrapped,
* start with the one that's further behind head
* (--> only *one* back seek required),
* since back seek takes more time than forward.
*/
if (s1 <= s2)
return rq1;
else
return rq2;
}
}
/*
* The below is leftmost cache rbtree addon
*/
static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
{
/* Service tree is empty */
if (!root->count)
return NULL;
if (!root->left)
root->left = rb_first(&root->rb);
if (root->left)
return rb_entry(root->left, struct cfq_queue, rb_node);
return NULL;
}
static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
{
if (!root->left)
root->left = rb_first(&root->rb);
if (root->left)
return rb_entry_cfqg(root->left);
return NULL;
}
static void rb_erase_init(struct rb_node *n, struct rb_root *root)
{
rb_erase(n, root);
RB_CLEAR_NODE(n);
}
static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
{
if (root->left == n)
root->left = NULL;
rb_erase_init(n, &root->rb);
--root->count;
}
/*
* would be nice to take fifo expire time into account as well
*/
static struct request *
cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
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 {
rbnext = rb_first(&cfqq->sort_list);
if (rbnext && rbnext != &last->rb_node)
next = rb_entry_rq(rbnext);
}
return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
}
static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
struct cfq_queue *cfqq)
{
/*
* just an approximation, should be ok.
*/
return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
}
static inline s64
cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
{
return cfqg->vdisktime - st->min_vdisktime;
}
static void
__cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
{
struct rb_node **node = &st->rb.rb_node;
struct rb_node *parent = NULL;
struct cfq_group *__cfqg;
s64 key = cfqg_key(st, cfqg);
int left = 1;
while (*node != NULL) {
parent = *node;
__cfqg = rb_entry_cfqg(parent);
if (key < cfqg_key(st, __cfqg))
node = &parent->rb_left;
else {
node = &parent->rb_right;
left = 0;
}
}
if (left)
st->left = &cfqg->rb_node;
rb_link_node(&cfqg->rb_node, parent, node);
rb_insert_color(&cfqg->rb_node, &st->rb);
}
static void
cfq_update_group_weight(struct cfq_group *cfqg)
{
BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
if (cfqg->needs_update) {
cfqg->weight = cfqg->new_weight;
cfqg->needs_update = false;
}
}
static void
cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
{
BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
cfq_update_group_weight(cfqg);
__cfq_group_service_tree_add(st, cfqg);
st->total_weight += cfqg->weight;
}
static void
cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
struct cfq_rb_root *st = &cfqd->grp_service_tree;
struct cfq_group *__cfqg;
struct rb_node *n;
cfqg->nr_cfqq++;
if (!RB_EMPTY_NODE(&cfqg->rb_node))
return;
/*
* Currently put the group at the end. Later implement something
* so that groups get lesser vtime based on their weights, so that
* if group does not loose all if it was not continuously backlogged.
*/
n = rb_last(&st->rb);
if (n) {
__cfqg = rb_entry_cfqg(n);
cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
} else
cfqg->vdisktime = st->min_vdisktime;
cfq_group_service_tree_add(st, cfqg);
}
static void
cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
{
st->total_weight -= cfqg->weight;
if (!RB_EMPTY_NODE(&cfqg->rb_node))
cfq_rb_erase(&cfqg->rb_node, st);
}
static void
cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
struct cfq_rb_root *st = &cfqd->grp_service_tree;
BUG_ON(cfqg->nr_cfqq < 1);
cfqg->nr_cfqq--;
/* If there are other cfq queues under this group, don't delete it */
if (cfqg->nr_cfqq)
return;
cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
cfq_group_service_tree_del(st, cfqg);
cfqg->saved_workload_slice = 0;
cfq_blkiocg_update_dequeue_stats(&cfqg->blkg, 1);
}
static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq,
unsigned int *unaccounted_time)
{
unsigned int slice_used;
/*
* Queue got expired before even a single request completed or
* got expired immediately after first request completion.
*/
if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
/*
* Also charge the seek time incurred to the group, otherwise
* if there are mutiple queues in the group, each can dispatch
* a single request on seeky media and cause lots of seek time
* and group will never know it.
*/
slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
1);
} else {
slice_used = jiffies - cfqq->slice_start;
if (slice_used > cfqq->allocated_slice) {
*unaccounted_time = slice_used - cfqq->allocated_slice;
slice_used = cfqq->allocated_slice;
}
if (time_after(cfqq->slice_start, cfqq->dispatch_start))
*unaccounted_time += cfqq->slice_start -
cfqq->dispatch_start;
}
return slice_used;
}
static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
struct cfq_queue *cfqq)
{
struct cfq_rb_root *st = &cfqd->grp_service_tree;
unsigned int used_sl, charge, unaccounted_sl = 0;
int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
- cfqg->service_tree_idle.count;
BUG_ON(nr_sync < 0);
used_sl = charge = cfq_cfqq_slice_usage(cfqq, &unaccounted_sl);
if (iops_mode(cfqd))
charge = cfqq->slice_dispatch;
else if (!cfq_cfqq_sync(cfqq) && !nr_sync)
charge = cfqq->allocated_slice;
/* Can't update vdisktime while group is on service tree */
cfq_group_service_tree_del(st, cfqg);
cfqg->vdisktime += cfq_scale_slice(charge, cfqg);
/* If a new weight was requested, update now, off tree */
cfq_group_service_tree_add(st, cfqg);
/* This group is being expired. Save the context */
if (time_after(cfqd->workload_expires, jiffies)) {
cfqg->saved_workload_slice = cfqd->workload_expires
- jiffies;
cfqg->saved_workload = cfqd->serving_type;