[PATCH 10/10] blkcg: remove cfqg_stats->sectors

Tejun Heo
2015-07-12T18:01:16Z

cfq_stats->sectors is a blkg_stat which keeps track of the total
number of sectors serviced; however, this can be trivially calculated
from blkcg_gq->stat_bytes. The only thing necessary is adding up
READs and WRITEs and then dividing by sector size.

Remove cfqg_stats->sectors and make cfq print "sectors" and
"sectors_recursive" from stat_bytes.

While this is a bit more code, it removes duplicate stat allocations
and updates and ensures that the reported stats stay in tune with each
other.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
---
block/cfq-iosched.c | 55 +++++++++++++++++++++++++++++++++++------------------
1 file changed, 36 insertions(+), 19 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 4c85c84..087772b 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -185,8 +185,6 @@ struct cfqg_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
@@ -688,12 +686,6 @@ static inline void cfqg_stats_update_io_merged(struct cfq_group *cfqg, int rw)
blkg_rwstat_add(&cfqg->stats.merged, rw, 1);
}

-static inline void cfqg_stats_update_dispatch(struct cfq_group *cfqg,
- uint64_t bytes, int rw)
-{
- blkg_stat_add(&cfqg->stats.sectors, bytes >> 9);
-}
-
static inline void cfqg_stats_update_completion(struct cfq_group *cfqg,
uint64_t start_time, uint64_t io_start_time, int rw)
{
@@ -782,8 +774,6 @@ static inline void cfqg_stats_update_timeslice_used(struct cfq_group *cfqg,
unsigned long time, unsigned long unaccounted_time) { }
static inline void cfqg_stats_update_io_remove(struct cfq_group *cfqg, int rw) { }
static inline void cfqg_stats_update_io_merged(struct cfq_group *cfqg, int rw) { }
-static inline void cfqg_stats_update_dispatch(struct cfq_group *cfqg,
- uint64_t bytes, int rw) { }
static inline void cfqg_stats_update_completion(struct cfq_group *cfqg,
uint64_t start_time, uint64_t io_start_time, int rw) { }

@@ -1538,8 +1528,6 @@ static void cfqg_stats_exit(struct cfqg_stats *stats)
blkg_rwstat_exit(&stats->service_time);
blkg_rwstat_exit(&stats->wait_time);
blkg_rwstat_exit(&stats->queued);
-
- blkg_stat_exit(&stats->sectors);
blkg_stat_exit(&stats->time);
#ifdef CONFIG_DEBUG_BLK_CGROUP
blkg_stat_exit(&stats->unaccounted_time);
@@ -1558,8 +1546,6 @@ static int cfqg_stats_init(struct cfqg_stats *stats, gfp_t 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;

@@ -1890,6 +1876,40 @@ static int cfqg_print_rwstat_recursive(struct seq_file *sf, void *v)
return 0;
}

+static u64 cfqg_prfill_sectors(struct seq_file *sf, struct blkg_policy_data *pd,
+ int off)
+{
+ u64 sum = blkg_rwstat_total(&pd->blkg->stat_bytes);
+
+ return __blkg_prfill_u64(sf, pd, sum >> 9);
+}
+
+static int cfqg_print_stat_sectors(struct seq_file *sf, void *v)
+{
+ blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
+ cfqg_prfill_sectors, &blkcg_policy_cfq, 0, false);
+ return 0;
+}
+
+static u64 cfqg_prfill_sectors_recursive(struct seq_file *sf,
+ struct blkg_policy_data *pd, int off)
+{
+ struct blkg_rwstat tmp = blkg_rwstat_recursive_sum(pd->blkg, NULL,
+ offsetof(struct blkcg_gq, stat_bytes));
+ u64 sum = atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_READ]) +
+ atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_WRITE]);
+
+ return __blkg_prfill_u64(sf, pd, sum >> 9);
+}
+
+static int cfqg_print_stat_sectors_recursive(struct seq_file *sf, void *v)
+{
+ blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
+ cfqg_prfill_sectors_recursive, &blkcg_policy_cfq, 0,
+ false);
+ return 0;
+}
+
#ifdef CONFIG_DEBUG_BLK_CGROUP
static u64 cfqg_prfill_avg_queue_size(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
@@ -1964,8 +1984,7 @@ static struct cftype cfq_blkcg_files[] = {
},
{
.name = "sectors",
- .private = offsetof(struct cfq_group, stats.sectors),
- .seq_show = cfqg_print_stat,
+ .seq_show = cfqg_print_stat_sectors,
},
{
.name = "io_service_bytes",
@@ -2006,8 +2025,7 @@ static struct cftype cfq_blkcg_files[] = {
},
{
.name = "sectors_recursive",
- .private = offsetof(struct cfq_group, stats.sectors),
- .seq_show = cfqg_print_stat_recursive,
+ .seq_show = cfqg_print_stat_sectors_recursive,
},
{
.name = "io_service_bytes_recursive",
@@ -2871,7 +2889,6 @@ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)

cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
cfqq->nr_sectors += blk_rq_sectors(rq);
- cfqg_stats_update_dispatch(cfqq->cfqg, blk_rq_bytes(rq), rq->cmd_flags);
}

/*
--
2.4.3