From: Zhaoyang Huang <[email protected]>
Over-limit bw value is observed during fio test in the throttling group
which caused by over-sized bio as there is no control on ra->size during
readahead. This series patches would like to introduce the helper
function to provide the bytes limit and apply it on readahead.
Please find below for the fio test result on v6.6 which presents 2%-10%
improvement for BW and lat. Besides, we can also observed stable BW
instantaneous value during the test.
blkio.throttle.read_bps_device = 1MB/s
before: read: IOPS=223, BW=894KiB/s (915kB/s)(175MiB/200919msec)
after : read: IOPS=239, BW=960KiB/s (983kB/s)(153MiB/163105msec)
before: clat (usec): min=4, max=16795k, avg=4468.74, stdev=265746.14
lat (usec): min=6, max=16795k, avg=4470.57, stdev=265746.14
after : clat (usec): min=11, max=209193, avg=4105.22, stdev=27188.04
lat (usec): min=16, max=209197, avg=4120.03, stdev=27188.04
blkio.throttle.read_bps_device = 10MB/s
before: read: IOPS=2380, BW=9524KiB/s (9752kB/s)(1007MiB/108311msec)
after : read: IOPS=2438, BW=9754KiB/s (9989kB/s)(1680MiB/176405msec)
before: clat (usec): min=4, max=201817, avg=399.58, stdev=8268.85
lat (usec): min=6, max=201819, avg=402.10, stdev=8268.85
after : clat (usec): min=4, max=2494.6k, avg=412.72, stdev=25783.51
lat (usec): min=6, max=2494.6k, avg=414.48, stdev=25783.51
Zhaoyang Huang (2):
block: introduce helper function to calculate bps budgt
mm: introduce budgt control in readahead
block/blk-throttle.c | 44 ++++++++++++++++++++++++++++++++++++++
include/linux/blk-cgroup.h | 10 +++++++++
mm/readahead.c | 33 ++++++++++++++++++++--------
3 files changed, 78 insertions(+), 9 deletions(-)
--
2.25.1
From: Zhaoyang Huang <[email protected]>
The 'over-sized' bio under blk throttle control will be delayed to
launch which breaks original IO timing and have the immediate BW be
not within the bps limit. Introduce a helper function to calculate block
device's budgt which provide the allowed bytes for current bio.
Signed-off-by: Zhaoyang Huang <[email protected]>
---
block/blk-throttle.c | 44 ++++++++++++++++++++++++++++++++++++++
include/linux/blk-cgroup.h | 10 +++++++++
2 files changed, 54 insertions(+)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index f4850a6f860b..41c75258183d 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -10,6 +10,7 @@
#include <linux/blkdev.h>
#include <linux/bio.h>
#include <linux/blktrace_api.h>
+#include <linux/cgroup.h>
#include "blk.h"
#include "blk-cgroup-rwstat.h"
#include "blk-stat.h"
@@ -2365,6 +2366,49 @@ void blk_throtl_bio_endio(struct bio *bio)
}
#endif
+unsigned long blk_throttle_budgt(struct block_device *bdev)
+{
+ struct request_queue *q = bdev_get_queue(bdev);
+ struct blkcg *blkcg;
+ struct blkcg_gq *blkg;
+ struct throtl_grp *tg;
+ long long bytes_allowed = 0;
+ unsigned long jiffy_elapsed, jiffy_elapsed_rnd;
+ u64 bps_limit;
+
+ if (!q)
+ return U64_MAX;
+
+ rcu_read_lock();
+ spin_lock_irq(&q->queue_lock);
+ blkcg = css_to_blkcg(task_css(current, io_cgrp_id));
+ if (!blkcg)
+ goto out;
+
+ blkg = blkg_lookup(blkcg, q);
+ if (!blkg || !blkg_tryget(blkg))
+ goto out;
+
+ tg = blkg_to_tg(blkg);
+ bps_limit = tg_bps_limit(tg, READ);
+ if (bps_limit == U64_MAX)
+ goto out;
+
+ jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[READ];
+ if (!jiffy_elapsed)
+ jiffy_elapsed_rnd = tg->td->throtl_slice;
+
+ jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
+ bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd) +
+ tg->carryover_bytes[READ];
+ blkg_put(blkg);
+out:
+ spin_unlock_irq(&q->queue_lock);
+ rcu_read_unlock();
+ return bytes_allowed;
+}
+
+
int blk_throtl_init(struct gendisk *disk)
{
struct request_queue *q = disk->queue;
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index dd5841a42c33..ba79fa464e0a 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -15,10 +15,12 @@
*/
#include <linux/types.h>
+#include <linux/limits.h>
struct bio;
struct cgroup_subsys_state;
struct gendisk;
+struct block_device;
#define FC_APPID_LEN 129
@@ -45,6 +47,14 @@ static inline struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio)
}
#endif /* CONFIG_BLK_CGROUP */
+#ifdef CONFIG_BLK_DEV_THROTTLING
+unsigned long blk_throttle_budgt(struct block_device *bdev);
+#else
+static inline unsigned long blk_throttle_budgt(struct block_device *bdev)
+{
+ return U64_MAX;
+}
+#endif
int blkcg_set_fc_appid(char *app_id, u64 cgrp_id, size_t app_id_len);
char *blkcg_get_fc_appid(struct bio *bio);
--
2.25.1