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blk-cgroup: introduce a new struct blkg_rwstat_sample

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When sampling the blkcg counts we don't need atomics or per-cpu
variables.  Introduce a new structure just containing plain u64
counters.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig
2019-06-06 12:26:21 +02:00
committed by Jens Axboe
parent 5d0b6e48cb
commit 7af6fd9112
3 changed files with 35 additions and 36 deletions
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22
include/linux/blk-cgroup.h
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@@ -63,8 +63,7 @@ struct blkcg {
/*
* blkg_[rw]stat->aux_cnt is excluded for local stats but included for
* recursive. Used to carry stats of dead children, and, for blkg_rwstat,
* to carry result values from read and sum operations.
* recursive. Used to carry stats of dead children.
*/
struct blkg_stat {
struct percpu_counter cpu_cnt;
@@ -76,6 +75,10 @@ struct blkg_rwstat {
atomic64_t aux_cnt[BLKG_RWSTAT_NR];
};
struct blkg_rwstat_sample {
u64 cnt[BLKG_RWSTAT_NR];
};
/*
* A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a
* request_queue (q). This is used by blkcg policies which need to track
@@ -213,7 +216,7 @@ void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
bool show_total);
u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v);
u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
const struct blkg_rwstat *rwstat);
const struct blkg_rwstat_sample *rwstat);
u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off);
u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
int off);
@@ -225,7 +228,7 @@ int blkg_print_stat_ios_recursive(struct seq_file *sf, void *v);
u64 blkg_stat_recursive_sum(struct blkcg_gq *blkg,
struct blkcg_policy *pol, int off);
void blkg_rwstat_recursive_sum(struct blkcg_gq *blkg, struct blkcg_policy *pol,
int off, struct blkg_rwstat *sum);
int off, struct blkg_rwstat_sample *sum);
struct blkg_conf_ctx {
struct gendisk *disk;
@@ -701,13 +704,13 @@ static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat,
* Read the current snapshot of @rwstat and return it in the aux counts.
*/
static inline void blkg_rwstat_read(struct blkg_rwstat *rwstat,
struct blkg_rwstat *result)
struct blkg_rwstat_sample *result)
{
int i;
for (i = 0; i < BLKG_RWSTAT_NR; i++)
atomic64_set(&result->aux_cnt[i],
percpu_counter_sum_positive(&rwstat->cpu_cnt[i]));
result->cnt[i] =
percpu_counter_sum_positive(&rwstat->cpu_cnt[i]);
}
/**
@@ -720,11 +723,10 @@ static inline void blkg_rwstat_read(struct blkg_rwstat *rwstat,
*/
static inline uint64_t blkg_rwstat_total(struct blkg_rwstat *rwstat)
{
struct blkg_rwstat tmp = { };
struct blkg_rwstat_sample tmp = { };
blkg_rwstat_read(rwstat, &tmp);
return atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_READ]) +
atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_WRITE]);
return tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE];
}
/**