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blkcg: make blkcg_[rw]stat per-cpu

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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: Tejun Heo <[email protected]>
Cc: Vivek Goyal <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Tejun Heo 2015-08-18 14:55:22 -07:00 • committed by Jens Axboe
commit 24bdb8ef06
4 changed files with 153 additions and 136 deletions
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10
block/blk-cgroup.c
View file

@ -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();