Commit 24bdb8ef authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe

blkcg: make blkcg_[rw]stat per-cpu

blkcg_[rw]stat are used as stat counters for blkcg policies.  It isn't
per-cpu by itself and blk-throttle makes it per-cpu by wrapping around
it.  This patch makes blkcg_[rw]stat per-cpu and drop the ad-hoc
per-cpu wrapping in blk-throttle.

* blkg_[rw]stat->cnt is replaced with cpu_cnt which is struct
  percpu_counter.  This makes syncp unnecessary as remote accesses are
  handled by percpu_counter itself.

* blkg_[rw]stat_init() can now fail due to percpu allocation failure
  and thus are updated to return int.

* percpu_counters need explicit freeing.  blkg_[rw]stat_exit() added.

* As blkg_rwstat->cpu_cnt[] can't be read directly anymore, reading
  and summing results are stored in ->aux_cnt[] instead.

* Custom per-cpu stat implementation in blk-throttle is removed.

This makes all blkcg stat counters per-cpu without complicating policy
implmentations.
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent e6269c44
......@@ -539,9 +539,10 @@ u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
for (i = 0; i < BLKG_RWSTAT_NR; i++)
seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
(unsigned long long)rwstat->cnt[i]);
(unsigned long long)atomic64_read(&rwstat->aux_cnt[i]));
v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE];
v = atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_READ]) +
atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_WRITE]);
seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
return v;
}
......@@ -643,8 +644,9 @@ struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkg_policy_data *pd,
tmp = blkg_rwstat_read(rwstat);
for (i = 0; i < BLKG_RWSTAT_NR; i++)
sum.cnt[i] += tmp.cnt[i] +
atomic64_read(&rwstat->aux_cnt[i]);
atomic64_add(atomic64_read(&tmp.aux_cnt[i]) +
atomic64_read(&rwstat->aux_cnt[i]),
&sum.aux_cnt[i]);
}
rcu_read_unlock();
......
......@@ -83,14 +83,6 @@ enum tg_state_flags {
#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
/* Per-cpu group stats */
struct tg_stats_cpu {
/* total bytes transferred */
struct blkg_rwstat service_bytes;
/* total IOs serviced, post merge */
struct blkg_rwstat serviced;
};
struct throtl_grp {
/* must be the first member */
struct blkg_policy_data pd;
......@@ -142,8 +134,10 @@ struct throtl_grp {
unsigned long slice_start[2];
unsigned long slice_end[2];
/* Per cpu stats pointer */
struct tg_stats_cpu __percpu *stats_cpu;
/* total bytes transferred */
struct blkg_rwstat service_bytes;
/* total IOs serviced, post merge */
struct blkg_rwstat serviced;
};
struct throtl_data
......@@ -337,17 +331,15 @@ static void throtl_service_queue_init(struct throtl_service_queue *sq)
static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
{
struct throtl_grp *tg;
int rw, cpu;
int rw;
tg = kzalloc_node(sizeof(*tg), gfp, node);
if (!tg)
return NULL;
goto err;
tg->stats_cpu = alloc_percpu_gfp(struct tg_stats_cpu, gfp);
if (!tg->stats_cpu) {
kfree(tg);
return NULL;
}
if (blkg_rwstat_init(&tg->service_bytes, gfp) ||
blkg_rwstat_init(&tg->serviced, gfp))
goto err_free_tg;
throtl_service_queue_init(&tg->service_queue);
......@@ -362,14 +354,14 @@ static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
tg->iops[READ] = -1;
tg->iops[WRITE] = -1;
for_each_possible_cpu(cpu) {
struct tg_stats_cpu *stats_cpu = per_cpu_ptr(tg->stats_cpu, cpu);
blkg_rwstat_init(&stats_cpu->service_bytes);
blkg_rwstat_init(&stats_cpu->serviced);
}
return &tg->pd;
err_free_tg:
blkg_rwstat_exit(&tg->serviced);
blkg_rwstat_exit(&tg->service_bytes);
kfree(tg);
err:
return NULL;
}
static void throtl_pd_init(struct blkg_policy_data *pd)
......@@ -427,21 +419,17 @@ static void throtl_pd_free(struct blkg_policy_data *pd)
struct throtl_grp *tg = pd_to_tg(pd);
del_timer_sync(&tg->service_queue.pending_timer);
free_percpu(tg->stats_cpu);
blkg_rwstat_exit(&tg->serviced);
blkg_rwstat_exit(&tg->service_bytes);
kfree(tg);
}
static void throtl_pd_reset_stats(struct blkg_policy_data *pd)
{
struct throtl_grp *tg = pd_to_tg(pd);
int cpu;
for_each_possible_cpu(cpu) {
struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
blkg_rwstat_reset(&sc->service_bytes);
blkg_rwstat_reset(&sc->serviced);
}
blkg_rwstat_reset(&tg->service_bytes);
blkg_rwstat_reset(&tg->serviced);
}
static struct throtl_grp *
......@@ -855,7 +843,6 @@ static void throtl_update_dispatch_stats(struct blkcg_gq *blkg, u64 bytes,
int rw)
{
struct throtl_grp *tg = blkg_to_tg(blkg);
struct tg_stats_cpu *stats_cpu;
unsigned long flags;
/*
......@@ -865,10 +852,8 @@ static void throtl_update_dispatch_stats(struct blkcg_gq *blkg, u64 bytes,
*/
local_irq_save(flags);
stats_cpu = this_cpu_ptr(tg->stats_cpu);
blkg_rwstat_add(&stats_cpu->serviced, rw, 1);
blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes);
blkg_rwstat_add(&tg->serviced, rw, 1);
blkg_rwstat_add(&tg->service_bytes, rw, bytes);
local_irq_restore(flags);
}
......@@ -1176,27 +1161,9 @@ static void blk_throtl_dispatch_work_fn(struct work_struct *work)
}
}
static u64 tg_prfill_cpu_rwstat(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
struct throtl_grp *tg = pd_to_tg(pd);
struct blkg_rwstat rwstat = { }, tmp;
int i, cpu;
for_each_possible_cpu(cpu) {
struct tg_stats_cpu *sc = per_cpu_ptr(tg->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);
}
static int tg_print_cpu_rwstat(struct seq_file *sf, void *v)
static int tg_print_rwstat(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_cpu_rwstat,
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_rwstat,
&blkcg_policy_throtl, seq_cft(sf)->private, true);
return 0;
}
......@@ -1337,13 +1304,13 @@ static struct cftype throtl_files[] = {
},
{
.name = "throttle.io_service_bytes",
.private = offsetof(struct tg_stats_cpu, service_bytes),
.seq_show = tg_print_cpu_rwstat,
.private = offsetof(struct throtl_grp, service_bytes),
.seq_show = tg_print_rwstat,
},
{
.name = "throttle.io_serviced",
.private = offsetof(struct tg_stats_cpu, serviced),
.seq_show = tg_print_cpu_rwstat,
.private = offsetof(struct throtl_grp, serviced),
.seq_show = tg_print_rwstat,
},
{ } /* terminate */
};
......
......@@ -1542,27 +1542,55 @@ static void cfq_init_cfqg_base(struct cfq_group *cfqg)
}
#ifdef CONFIG_CFQ_GROUP_IOSCHED
static void cfqg_stats_init(struct cfqg_stats *stats)
static void cfqg_stats_exit(struct cfqg_stats *stats)
{
blkg_rwstat_init(&stats->service_bytes);
blkg_rwstat_init(&stats->serviced);
blkg_rwstat_init(&stats->merged);
blkg_rwstat_init(&stats->service_time);
blkg_rwstat_init(&stats->wait_time);
blkg_rwstat_init(&stats->queued);
blkg_rwstat_exit(&stats->service_bytes);
blkg_rwstat_exit(&stats->serviced);
blkg_rwstat_exit(&stats->merged);
blkg_rwstat_exit(&stats->service_time);
blkg_rwstat_exit(&stats->wait_time);
blkg_rwstat_exit(&stats->queued);
blkg_stat_init(&stats->sectors);
blkg_stat_init(&stats->time);
blkg_stat_exit(&stats->sectors);
blkg_stat_exit(&stats->time);
#ifdef CONFIG_DEBUG_BLK_CGROUP
blkg_stat_exit(&stats->unaccounted_time);
blkg_stat_exit(&stats->avg_queue_size_sum);
blkg_stat_exit(&stats->avg_queue_size_samples);
blkg_stat_exit(&stats->dequeue);
blkg_stat_exit(&stats->group_wait_time);
blkg_stat_exit(&stats->idle_time);
blkg_stat_exit(&stats->empty_time);
#endif
}
static int cfqg_stats_init(struct cfqg_stats *stats, gfp_t gfp)
{
if (blkg_rwstat_init(&stats->service_bytes, gfp) ||
blkg_rwstat_init(&stats->serviced, gfp) ||
blkg_rwstat_init(&stats->merged, gfp) ||
blkg_rwstat_init(&stats->service_time, gfp) ||
blkg_rwstat_init(&stats->wait_time, gfp) ||
blkg_rwstat_init(&stats->queued, gfp) ||
blkg_stat_init(&stats->sectors, gfp) ||
blkg_stat_init(&stats->time, gfp))
goto err;
#ifdef CONFIG_DEBUG_BLK_CGROUP
blkg_stat_init(&stats->unaccounted_time);
blkg_stat_init(&stats->avg_queue_size_sum);
blkg_stat_init(&stats->avg_queue_size_samples);
blkg_stat_init(&stats->dequeue);
blkg_stat_init(&stats->group_wait_time);
blkg_stat_init(&stats->idle_time);
blkg_stat_init(&stats->empty_time);
if (blkg_stat_init(&stats->unaccounted_time, gfp) ||
blkg_stat_init(&stats->avg_queue_size_sum, gfp) ||
blkg_stat_init(&stats->avg_queue_size_samples, gfp) ||
blkg_stat_init(&stats->dequeue, gfp) ||
blkg_stat_init(&stats->group_wait_time, gfp) ||
blkg_stat_init(&stats->idle_time, gfp) ||
blkg_stat_init(&stats->empty_time, gfp))
goto err;
#endif
return 0;
err:
cfqg_stats_exit(stats);
return -ENOMEM;
}
static struct blkcg_policy_data *cfq_cpd_alloc(gfp_t gfp)
......@@ -1602,7 +1630,10 @@ static struct blkg_policy_data *cfq_pd_alloc(gfp_t gfp, int node)
return NULL;
cfq_init_cfqg_base(cfqg);
cfqg_stats_init(&cfqg->stats);
if (cfqg_stats_init(&cfqg->stats, gfp)) {
kfree(cfqg);
return NULL;
}
return &cfqg->pd;
}
......@@ -1642,7 +1673,10 @@ static void cfq_pd_offline(struct blkg_policy_data *pd)
static void cfq_pd_free(struct blkg_policy_data *pd)
{
return kfree(pd);
struct cfq_group *cfqg = pd_to_cfqg(pd);
cfqg_stats_exit(&cfqg->stats);
return kfree(cfqg);
}
static void cfq_pd_reset_stats(struct blkg_policy_data *pd)
......
......@@ -14,12 +14,15 @@
*/
#include <linux/cgroup.h>
#include <linux/u64_stats_sync.h>
#include <linux/percpu_counter.h>
#include <linux/seq_file.h>
#include <linux/radix-tree.h>
#include <linux/blkdev.h>
#include <linux/atomic.h>
/* percpu_counter batch for blkg_[rw]stats, per-cpu drift doesn't matter */
#define BLKG_STAT_CPU_BATCH (INT_MAX / 2)
/* Max limits for throttle policy */
#define THROTL_IOPS_MAX UINT_MAX
......@@ -55,17 +58,16 @@ struct blkcg {
/*
* blkg_[rw]stat->aux_cnt is excluded for local stats but included for
* recursive. Used to carry stats of dead children.
* recursive. Used to carry stats of dead children, and, for blkg_rwstat,
* to carry result values from read and sum operations.
*/
struct blkg_stat {
struct u64_stats_sync syncp;
uint64_t cnt;
struct percpu_counter cpu_cnt;
atomic64_t aux_cnt;
};
struct blkg_rwstat {
struct u64_stats_sync syncp;
uint64_t cnt[BLKG_RWSTAT_NR];
struct percpu_counter cpu_cnt[BLKG_RWSTAT_NR];
atomic64_t aux_cnt[BLKG_RWSTAT_NR];
};
......@@ -486,10 +488,21 @@ struct request_list *__blk_queue_next_rl(struct request_list *rl,
#define blk_queue_for_each_rl(rl, q) \
for ((rl) = &(q)->root_rl; (rl); (rl) = __blk_queue_next_rl((rl), (q)))
static inline void blkg_stat_init(struct blkg_stat *stat)
static inline int blkg_stat_init(struct blkg_stat *stat, gfp_t gfp)
{
u64_stats_init(&stat->syncp);
int ret;
ret = percpu_counter_init(&stat->cpu_cnt, 0, gfp);
if (ret)
return ret;
atomic64_set(&stat->aux_cnt, 0);
return 0;
}
static inline void blkg_stat_exit(struct blkg_stat *stat)
{
percpu_counter_destroy(&stat->cpu_cnt);
}
/**
......@@ -497,35 +510,21 @@ static inline void blkg_stat_init(struct blkg_stat *stat)
* @stat: target blkg_stat
* @val: value to add
*
* Add @val to @stat. The caller is responsible for synchronizing calls to
* this function.
* Add @val to @stat. The caller must ensure that IRQ on the same CPU
* don't re-enter this function for the same counter.
*/
static inline void blkg_stat_add(struct blkg_stat *stat, uint64_t val)
{
u64_stats_update_begin(&stat->syncp);
stat->cnt += val;
u64_stats_update_end(&stat->syncp);
__percpu_counter_add(&stat->cpu_cnt, val, BLKG_STAT_CPU_BATCH);
}
/**
* blkg_stat_read - read the current value of a blkg_stat
* @stat: blkg_stat to read
*
* Read the current value of @stat. The returned value doesn't include the
* aux count. This function can be called without synchroniztion and takes
* care of u64 atomicity.
*/
static inline uint64_t blkg_stat_read(struct blkg_stat *stat)
{
unsigned int start;
uint64_t v;
do {
start = u64_stats_fetch_begin_irq(&stat->syncp);
v = stat->cnt;
} while (u64_stats_fetch_retry_irq(&stat->syncp, start));
return v;
return percpu_counter_sum_positive(&stat->cpu_cnt);
}
/**
......@@ -534,7 +533,7 @@ static inline uint64_t blkg_stat_read(struct blkg_stat *stat)
*/
static inline void blkg_stat_reset(struct blkg_stat *stat)
{
stat->cnt = 0;
percpu_counter_set(&stat->cpu_cnt, 0);
atomic64_set(&stat->aux_cnt, 0);
}
......@@ -552,14 +551,28 @@ static inline void blkg_stat_add_aux(struct blkg_stat *to,
&to->aux_cnt);
}
static inline void blkg_rwstat_init(struct blkg_rwstat *rwstat)
static inline int blkg_rwstat_init(struct blkg_rwstat *rwstat, gfp_t gfp)
{
int i;
int i, ret;
for (i = 0; i < BLKG_RWSTAT_NR; i++) {
ret = percpu_counter_init(&rwstat->cpu_cnt[i], 0, gfp);
if (ret) {
while (--i >= 0)
percpu_counter_destroy(&rwstat->cpu_cnt[i]);
return ret;
}
atomic64_set(&rwstat->aux_cnt[i], 0);
}
return 0;
}
u64_stats_init(&rwstat->syncp);
static inline void blkg_rwstat_exit(struct blkg_rwstat *rwstat)
{
int i;
for (i = 0; i < BLKG_RWSTAT_NR; i++)
atomic64_set(&rwstat->aux_cnt[i], 0);
percpu_counter_destroy(&rwstat->cpu_cnt[i]);
}
/**
......@@ -574,39 +587,38 @@ static inline void blkg_rwstat_init(struct blkg_rwstat *rwstat)
static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat,
int rw, uint64_t val)
{
u64_stats_update_begin(&rwstat->syncp);
struct percpu_counter *cnt;
if (rw & REQ_WRITE)
rwstat->cnt[BLKG_RWSTAT_WRITE] += val;
cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_WRITE];
else
rwstat->cnt[BLKG_RWSTAT_READ] += val;
cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_READ];
__percpu_counter_add(cnt, val, BLKG_STAT_CPU_BATCH);
if (rw & REQ_SYNC)
rwstat->cnt[BLKG_RWSTAT_SYNC] += val;
cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_SYNC];
else
rwstat->cnt[BLKG_RWSTAT_ASYNC] += val;
cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_ASYNC];
u64_stats_update_end(&rwstat->syncp);
__percpu_counter_add(cnt, val, BLKG_STAT_CPU_BATCH);
}
/**
* blkg_rwstat_read - read the current values of a blkg_rwstat
* @rwstat: blkg_rwstat to read
*
* Read the current snapshot of @rwstat and return it as the return value.
* This function can be called without synchronization and takes care of
* u64 atomicity.
* Read the current snapshot of @rwstat and return it in the aux counts.
*/
static inline struct blkg_rwstat blkg_rwstat_read(struct blkg_rwstat *rwstat)
{
unsigned int start;
struct blkg_rwstat tmp;
do {
start = u64_stats_fetch_begin_irq(&rwstat->syncp);
tmp = *rwstat;
} while (u64_stats_fetch_retry_irq(&rwstat->syncp, start));
struct blkg_rwstat result;
int i;
return tmp;
for (i = 0; i < BLKG_RWSTAT_NR; i++)
atomic64_set(&result.aux_cnt[i],
percpu_counter_sum_positive(&rwstat->cpu_cnt[i]));
return result;
}
/**
......@@ -621,7 +633,8 @@ static inline uint64_t blkg_rwstat_total(struct blkg_rwstat *rwstat)
{
struct blkg_rwstat tmp = blkg_rwstat_read(rwstat);
return tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE];
return atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_READ]) +
atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_WRITE]);
}
/**
......@@ -632,10 +645,10 @@ static inline void blkg_rwstat_reset(struct blkg_rwstat *rwstat)
{
int i;
memset(rwstat->cnt, 0, sizeof(rwstat->cnt));
for (i = 0; i < BLKG_RWSTAT_NR; i++)
for (i = 0; i < BLKG_RWSTAT_NR; i++) {
percpu_counter_set(&rwstat->cpu_cnt[i], 0);
atomic64_set(&rwstat->aux_cnt[i], 0);
}
}
/**
......@@ -652,7 +665,8 @@ static inline void blkg_rwstat_add_aux(struct blkg_rwstat *to,
int i;
for (i = 0; i < BLKG_RWSTAT_NR; i++)
atomic64_add(v.cnt[i] + atomic64_read(&from->aux_cnt[i]),
atomic64_add(atomic64_read(&v.aux_cnt[i]) +
atomic64_read(&from->aux_cnt[i]),
&to->aux_cnt[i]);
}
......
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