blkcg: don't use percpu for merged stats

With recent plug merge updates, merged stats are no longer called for
plug merges and now only updated while holding queue_lock.  As
stats_lock is scheduled to be removed, there's no reason to use percpu
for merged stats.  Don't use percpu for merged stats.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 622fb41432264e32007ae6ad30a9bfbab39145f3..6eedf3afa2761b27415babf2c37f5783b9ebfad0 100644 (file)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -451,27 +451,13 @@ void blkiocg_update_io_merged_stats(struct blkio_group *blkg,
                                    bool direction, bool sync)
 {
        struct blkg_policy_data *pd = blkg->pd[pol->plid];
-       struct blkio_group_stats_cpu *stats_cpu;
+       struct blkio_group_stats *stats;
        unsigned long flags;
 
-       /* If per cpu stats are not allocated yet, don't do any accounting. */
-       if (pd->stats_cpu == NULL)
-               return;
-
-       /*
-        * 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(pd->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);
+       spin_lock_irqsave(&blkg->stats_lock, flags);
+       stats = &pd->stats;
+       blkio_add_stat(stats->stat_arr[BLKIO_STAT_MERGED], 1, direction, sync);
+       spin_unlock_irqrestore(&blkg->stats_lock, flags);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_io_merged_stats);
 
@@ -1342,7 +1328,7 @@ 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_CPU_MERGED, 1, 1);
+                                               BLKIO_STAT_MERGED, 1, 0);
                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 1de32fe0e2afa5a030b739f691cf66b16cda0331..6c8e3e3454266741edad186727018173f9d14ef3 100644 (file)
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -29,10 +29,12 @@ enum blkio_policy_id {
 #ifdef CONFIG_BLK_CGROUP
 
 enum stat_type {
+       /* Number of IOs merged */
+       BLKIO_STAT_MERGED,
        /* Total time spent (in ns) between request dispatch to the driver and
         * request completion for IOs doen by this cgroup. This may not be
         * accurate when NCQ is turned on. */
-       BLKIO_STAT_SERVICE_TIME = 0,
+       BLKIO_STAT_SERVICE_TIME,
        /* Total time spent waiting in scheduler queue in ns */
        BLKIO_STAT_WAIT_TIME,
        /* Number of IOs queued up */
@@ -57,8 +59,6 @@ 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
 };