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blkcg: cfq doesn't need per-cpu dispatch stats
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blkio_group_stats_cpu is used to count dispatch stats using per-cpu
counters.  This is used by both blk-throtl and cfq-iosched but the
sharing is rather silly.

* cfq-iosched doesn't need per-cpu dispatch stats.  cfq always updates
  those stats while holding queue_lock.

* blk-throtl needs per-cpu dispatch stats but only service_bytes and
  serviced.  It doesn't make use of sectors.

This patch makes cfq add and use global stats for service_bytes,
serviced and sectors, removes per-cpu sectors counter and moves
per-cpu stat printing code to blk-throttle.c.

Signed-off-by: Tejun Heo <tj@kernel.org>
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@htejun
htejun committed Apr 1, 2012
1 parent 629ed0b commit 41b38b6
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Showing 4 changed files with 48 additions and 95 deletions.
63 changes: 2 additions & 61 deletions block/blk-cgroup.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -390,7 +390,6 @@ static void blkio_reset_stats_cpu(struct blkio_group *blkg, int plid)

blkg_rwstat_reset(&sc->service_bytes);
blkg_rwstat_reset(&sc->serviced);
blkg_stat_reset(&sc->sectors);
}
}

Expand All @@ -417,6 +416,8 @@ blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
struct blkio_group_stats *stats = &pd->stats;

/* queued stats shouldn't be cleared */
blkg_rwstat_reset(&stats->service_bytes);
blkg_rwstat_reset(&stats->serviced);
blkg_rwstat_reset(&stats->merged);
blkg_rwstat_reset(&stats->service_time);
blkg_rwstat_reset(&stats->wait_time);
Expand Down Expand Up @@ -577,66 +578,6 @@ int blkcg_print_rwstat(struct cgroup *cgrp, struct cftype *cft,
}
EXPORT_SYMBOL_GPL(blkcg_print_rwstat);

static u64 blkg_prfill_cpu_stat(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
u64 v = 0;
int cpu;

for_each_possible_cpu(cpu) {
struct blkio_group_stats_cpu *sc =
per_cpu_ptr(pd->stats_cpu, cpu);

v += blkg_stat_read((void *)sc + off);
}

return __blkg_prfill_u64(sf, pd, v);
}

static u64 blkg_prfill_cpu_rwstat(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
struct blkg_rwstat rwstat = { }, tmp;
int i, cpu;

for_each_possible_cpu(cpu) {
struct blkio_group_stats_cpu *sc =
per_cpu_ptr(pd->stats_cpu, cpu);

tmp = blkg_rwstat_read((void *)sc + off);
for (i = 0; i < BLKG_RWSTAT_NR; i++)
rwstat.cnt[i] += tmp.cnt[i];
}

return __blkg_prfill_rwstat(sf, pd, &rwstat);
}

/* print per-cpu blkg_stat specified by BLKCG_STAT_PRIV() */
int blkcg_print_cpu_stat(struct cgroup *cgrp, struct cftype *cft,
struct seq_file *sf)
{
struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);

blkcg_print_blkgs(sf, blkcg, blkg_prfill_cpu_stat,
BLKCG_STAT_POL(cft->private),
BLKCG_STAT_OFF(cft->private), false);
return 0;
}
EXPORT_SYMBOL_GPL(blkcg_print_cpu_stat);

/* print per-cpu blkg_rwstat specified by BLKCG_STAT_PRIV() */
int blkcg_print_cpu_rwstat(struct cgroup *cgrp, struct cftype *cft,
struct seq_file *sf)
{
struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);

blkcg_print_blkgs(sf, blkcg, blkg_prfill_cpu_rwstat,
BLKCG_STAT_POL(cft->private),
BLKCG_STAT_OFF(cft->private), true);
return 0;
}
EXPORT_SYMBOL_GPL(blkcg_print_cpu_rwstat);

/**
* blkg_conf_prep - parse and prepare for per-blkg config update
* @blkcg: target block cgroup
Expand Down
12 changes: 6 additions & 6 deletions block/blk-cgroup.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,10 @@ struct blkg_rwstat {
};

struct blkio_group_stats {
/* total bytes transferred */
struct blkg_rwstat service_bytes;
/* total IOs serviced, post merge */
struct blkg_rwstat serviced;
/* number of ios merged */
struct blkg_rwstat merged;
/* total time spent on device in ns, may not be accurate w/ queueing */
Expand All @@ -73,6 +77,8 @@ struct blkio_group_stats {
struct blkg_rwstat wait_time;
/* number of IOs queued up */
struct blkg_rwstat queued;
/* total sectors transferred */
struct blkg_stat sectors;
/* total disk time and nr sectors dispatched by this group */
struct blkg_stat time;
#ifdef CONFIG_DEBUG_BLK_CGROUP
Expand Down Expand Up @@ -104,8 +110,6 @@ struct blkio_group_stats_cpu {
struct blkg_rwstat service_bytes;
/* total IOs serviced, post merge */
struct blkg_rwstat serviced;
/* total sectors transferred */
struct blkg_stat sectors;
};

struct blkio_group_conf {
Expand Down Expand Up @@ -183,10 +187,6 @@ int blkcg_print_stat(struct cgroup *cgrp, struct cftype *cft,
struct seq_file *sf);
int blkcg_print_rwstat(struct cgroup *cgrp, struct cftype *cft,
struct seq_file *sf);
int blkcg_print_cpu_stat(struct cgroup *cgrp, struct cftype *cft,
struct seq_file *sf);
int blkcg_print_cpu_rwstat(struct cgroup *cgrp, struct cftype *cft,
struct seq_file *sf);

struct blkg_conf_ctx {
struct gendisk *disk;
Expand Down
31 changes: 30 additions & 1 deletion block/blk-throttle.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -582,7 +582,6 @@ static void throtl_update_dispatch_stats(struct blkio_group *blkg, u64 bytes,

stats_cpu = this_cpu_ptr(pd->stats_cpu);

blkg_stat_add(&stats_cpu->sectors, bytes >> 9);
blkg_rwstat_add(&stats_cpu->serviced, rw, 1);
blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes);

Expand Down Expand Up @@ -843,6 +842,36 @@ static void throtl_update_blkio_group_common(struct throtl_data *td,
throtl_schedule_delayed_work(td, 0);
}

static u64 blkg_prfill_cpu_rwstat(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
struct blkg_rwstat rwstat = { }, tmp;
int i, cpu;

for_each_possible_cpu(cpu) {
struct blkio_group_stats_cpu *sc =
per_cpu_ptr(pd->stats_cpu, cpu);

tmp = blkg_rwstat_read((void *)sc + off);
for (i = 0; i < BLKG_RWSTAT_NR; i++)
rwstat.cnt[i] += tmp.cnt[i];
}

return __blkg_prfill_rwstat(sf, pd, &rwstat);
}

/* print per-cpu blkg_rwstat specified by BLKCG_STAT_PRIV() */
static int blkcg_print_cpu_rwstat(struct cgroup *cgrp, struct cftype *cft,
struct seq_file *sf)
{
struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);

blkcg_print_blkgs(sf, blkcg, blkg_prfill_cpu_rwstat,
BLKCG_STAT_POL(cft->private),
BLKCG_STAT_OFF(cft->private), true);
return 0;
}

static u64 blkg_prfill_conf_u64(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
Expand Down
37 changes: 10 additions & 27 deletions block/cfq-iosched.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -624,29 +624,12 @@ static inline void cfq_blkiocg_update_dispatch_stats(struct blkio_group *blkg,
struct blkio_policy_type *pol, uint64_t bytes,
bool direction, bool sync)
{
struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
int rw = (direction ? REQ_WRITE : 0) | (sync ? REQ_SYNC : 0);
struct blkg_policy_data *pd = blkg->pd[pol->plid];
struct blkio_group_stats_cpu *stats_cpu;
unsigned long flags;

/* If per cpu stats are not allocated yet, don't do any accounting. */
if (pd->stats_cpu == NULL)
return;

/*
* Disabling interrupts to provide mutual exclusion between two
* writes on same cpu. It probably is not needed for 64bit. Not
* optimizing that case yet.
*/
local_irq_save(flags);

stats_cpu = this_cpu_ptr(pd->stats_cpu);

blkg_stat_add(&stats_cpu->sectors, bytes >> 9);
blkg_rwstat_add(&stats_cpu->serviced, rw, 1);
blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes);

local_irq_restore(flags);
blkg_stat_add(&stats->sectors, bytes >> 9);
blkg_rwstat_add(&stats->serviced, rw, 1);
blkg_rwstat_add(&stats->service_bytes, rw, bytes);
}

static inline void cfq_blkiocg_update_completion_stats(struct blkio_group *blkg,
Expand Down Expand Up @@ -1520,20 +1503,20 @@ static struct cftype cfq_blkcg_files[] = {
{
.name = "sectors",
.private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
offsetof(struct blkio_group_stats_cpu, sectors)),
.read_seq_string = blkcg_print_cpu_stat,
offsetof(struct blkio_group_stats, sectors)),
.read_seq_string = blkcg_print_stat,
},
{
.name = "io_service_bytes",
.private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
offsetof(struct blkio_group_stats_cpu, service_bytes)),
.read_seq_string = blkcg_print_cpu_rwstat,
offsetof(struct blkio_group_stats, service_bytes)),
.read_seq_string = blkcg_print_rwstat,
},
{
.name = "io_serviced",
.private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
offsetof(struct blkio_group_stats_cpu, serviced)),
.read_seq_string = blkcg_print_cpu_rwstat,
offsetof(struct blkio_group_stats, serviced)),
.read_seq_string = blkcg_print_rwstat,
},
{
.name = "io_service_time",
Expand Down

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