From: Tao Ma <boyu...@taobao.com>
Currently, if the IO is throttled by io-throttle, the SA has no idea of
the situation and can't report it to the real application user about
that he/she has to do something. So this patch adds a new interface
named blkio.throttle.io_queued which indicates how many IOs are
currently throttled.
Also another function blkg_rwstat_dec is added since the number of throttled
IOs can be either added or decreased.
Cc: Tejun Heo <t...@kernel.org>
Cc: Vivek Goyal <vgo...@redhat.com>
Cc: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Tao Ma <boyu...@taobao.com>
---
block/blk-cgroup.h | 26 ++++++++++++++++++++++++++
block/blk-throttle.c | 37 +++++++++++++++++++++++++++++++++++++
2 files changed, 63 insertions(+), 0 deletions(-)
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 2459730..b1f6f5c 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -413,6 +413,32 @@ static inline void blkg_rwstat_add(struct blkg_rwstat
*rwstat,
}
/**
+ * blkg_rwstat_dec - dec a value to a blkg_rwstat
+ * @rwstat: target blkg_rwstat
+ * @rw: mask of REQ_{WRITE|SYNC}
+ * @val: value to dec
+ *
+ * Dec @val to @rwstat. The counters are chosen according to @rw. The
+ * caller is responsible for synchronizing calls to this function.
+ */
+static inline void blkg_rwstat_dec(struct blkg_rwstat *rwstat,
+ int rw, uint64_t val)
+{
+ u64_stats_update_begin(&rwstat->syncp);
+
+ if (rw & REQ_WRITE)
+ rwstat->cnt[BLKG_RWSTAT_WRITE] -= val;
+ else
+ rwstat->cnt[BLKG_RWSTAT_READ] -= val;
+ if (rw & REQ_SYNC)
+ rwstat->cnt[BLKG_RWSTAT_SYNC] -= val;
+ else
+ rwstat->cnt[BLKG_RWSTAT_ASYNC] -= val;
+
+ u64_stats_update_end(&rwstat->syncp);
+}
+
+/**
* blkg_rwstat_read - read the current values of a blkg_rwstat
* @rwstat: blkg_rwstat to read
*
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 1588c2d..9317d71 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -46,6 +46,8 @@ struct tg_stats_cpu {
struct blkg_rwstat service_bytes;
/* total IOs serviced, post merge */
struct blkg_rwstat serviced;
+ /* total IOs queued, not submitted to the underlying device. */
+ struct blkg_rwstat io_queued;
};
struct throtl_grp {
@@ -267,6 +269,7 @@ static void throtl_pd_reset_stats(struct blkcg_gq *blkg)
blkg_rwstat_reset(&sc->service_bytes);
blkg_rwstat_reset(&sc->serviced);
+ blkg_rwstat_reset(&sc->io_queued);
}
}
@@ -700,6 +703,31 @@ static void throtl_update_dispatch_stats(struct throtl_grp
*tg, u64 bytes,
local_irq_restore(flags);
}
+static void throtl_update_queued_stats(struct throtl_grp *tg, int rw, int add)
+{
+ struct tg_stats_cpu *stats_cpu;
+ unsigned long flags;
+
+ /* If per cpu stats are not allocated yet, don't do any accounting. */
+ if (tg->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(tg->stats_cpu);
+ if (add)
+ blkg_rwstat_add(&stats_cpu->io_queued, rw, 1);
+ else
+ blkg_rwstat_dec(&stats_cpu->io_queued, rw, 1);
+
+ local_irq_restore(flags);
+}
+
static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
{
bool rw = bio_data_dir(bio);
@@ -715,6 +743,8 @@ static void throtl_add_bio_tg(struct throtl_data *td,
struct throtl_grp *tg,
struct bio *bio)
{
bool rw = bio_data_dir(bio);
+ struct tg_stats_cpu *stats_cpu;
+ unsigned long flags;
bio_list_add(&tg->bio_lists[rw], bio);
/* Take a bio reference on tg */
@@ -722,6 +752,7 @@ static void throtl_add_bio_tg(struct throtl_data *td,
struct throtl_grp *tg,
tg->nr_queued[rw]++;
td->nr_queued[rw]++;
throtl_enqueue_tg(td, tg);
+ throtl_update_queued_stats(tg, bio->bi_rw, 1);
}
static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg)
@@ -762,6 +793,7 @@ static void tg_dispatch_one_bio(struct throtl_data *td,
struct throtl_grp *tg,
bio->bi_rw |= REQ_THROTTLED;
throtl_trim_slice(td, tg, rw);
+ throtl_update_queued_stats(tg, bio->bi_rw, 0);
}
static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
@@ -1090,6 +1122,11 @@ static struct cftype throtl_files[] = {
.private = offsetof(struct tg_stats_cpu, serviced),
.read_seq_string = tg_print_cpu_rwstat,
},
+ {
+ .name = "throttle.io_queued",
+ .private = offsetof(struct tg_stats_cpu, io_queued),
+ .read_seq_string = tg_print_cpu_rwstat,
+ },
{ } /* terminate */
};
--
1.7.0.4
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