[RFC,0/2] introduce budgt control in readahead

Message

zhaoyang.huang May 9, 2024, 2:39 a.m. UTC

From: Zhaoyang Huang <[e-mail]>

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(-)