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

block/blk-cgroup.c

+6 −4
Original line number Diff line number Diff line
@@ -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();

block/blk-throttle.c

+28 −61
Original line number Diff line number Diff line
@@ -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 */

};

block/cfq-iosched.c

+52 −18
Original line number Diff line number Diff line
@@ -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)

include/linux/blk-cgroup.h

+67 −53
Original line number Diff line number Diff line
@@ -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]);

}



/**
@@ -632,11 +645,11 @@ 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);

	}

}



/**

 * blkg_rwstat_add_aux - add a blkg_rwstat into another's aux count
@@ -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]);

}