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Subject[PATCH 2/3] cfq-iosched: Make IO merge related stats per cpu
Date
Make BLKIO_STAT_MERGED per cpu hence gettring rid of need of taking
blkg->stats_lock.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
block/blk-cgroup.c | 22 +++++++++++++++++-----
block/blk-cgroup.h | 4 ++--
2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index e41cc6f..07371cf 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -441,15 +441,27 @@ void blkiocg_update_completion_stats(struct blkio_group *blkg,
}
EXPORT_SYMBOL_GPL(blkiocg_update_completion_stats);

+/* Merged stats are per cpu. */
void blkiocg_update_io_merged_stats(struct blkio_group *blkg, bool direction,
bool sync)
{
+ struct blkio_group_stats_cpu *stats_cpu;
unsigned long flags;

- spin_lock_irqsave(&blkg->stats_lock, flags);
- blkio_add_stat(blkg->stats.stat_arr[BLKIO_STAT_MERGED], 1, direction,
- sync);
- spin_unlock_irqrestore(&blkg->stats_lock, flags);
+ /*
+ * Disabling interrupts to provide mutual exclusion between two
+ * writes on same cpu. It probably is not needed for 64bit. Not
+ * optimizing that case yet.
+ */
+ local_irq_save(flags);
+
+ stats_cpu = this_cpu_ptr(blkg->stats_cpu);
+
+ u64_stats_update_begin(&stats_cpu->syncp);
+ blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_MERGED], 1,
+ direction, sync);
+ u64_stats_update_end(&stats_cpu->syncp);
+ local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(blkiocg_update_io_merged_stats);

@@ -1244,7 +1256,7 @@ static int blkiocg_file_read_map(struct cgroup *cgrp, struct cftype *cft,
BLKIO_STAT_WAIT_TIME, 1, 0);
case BLKIO_PROP_io_merged:
return blkio_read_blkg_stats(blkcg, cft, cb,
- BLKIO_STAT_MERGED, 1, 0);
+ BLKIO_STAT_CPU_MERGED, 1, 1);
case BLKIO_PROP_io_queued:
return blkio_read_blkg_stats(blkcg, cft, cb,
BLKIO_STAT_QUEUED, 1, 0);
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 2622267..a71d290 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -39,8 +39,6 @@ enum stat_type {
BLKIO_STAT_SERVICE_TIME = 0,
/* Total time spent waiting in scheduler queue in ns */
BLKIO_STAT_WAIT_TIME,
- /* Number of IOs merged */
- BLKIO_STAT_MERGED,
/* Number of IOs queued up */
BLKIO_STAT_QUEUED,
/* All the single valued stats go below this */
@@ -63,6 +61,8 @@ enum stat_type_cpu {
BLKIO_STAT_CPU_SERVICE_BYTES,
/* Total IOs serviced, post merge */
BLKIO_STAT_CPU_SERVICED,
+ /* Number of IOs merged */
+ BLKIO_STAT_CPU_MERGED,
BLKIO_STAT_CPU_NR
};

--
1.7.4.4


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