From: Chunguang Xu <brookxu@xxxxxxxxxxx> Tasks in the production environment can be roughly divided into three categories: emergency tasks, ordinary tasks and offline tasks. Emergency tasks need to be scheduled in real time, such as system agents. Offline tasks do not need to guarantee QoS, but can improve system resource utilization during system idle periods, such as background tasks. The above requirements need to achieve IO preemption. At present, we can use weights to simulate IO preemption, but since weights are more of a shared concept, they cannot be simulated well. For example, the weights of emergency tasks and ordinary tasks cannot be determined well, offline tasks (with the same weight) actually occupy different resources on disks with different performance, and the tail latency caused by offline tasks cannot be well controlled. Using ioprio's concept of preemption, we can solve the above problems very well. Since ioprio will eventually be converted to weight, using ioprio alone can also achieve weight isolation within the same class. But we can still use bfq.weight to control resource, achieving better IO Qos control. However, currently the class of bfq_group is always be class, and the ioprio class of the task can only be reflected in a single cgroup. We cannot guarantee that real-time tasks in a cgroup are scheduled in time. Therefore, we introduce bfq.ioprio, which allows us to configure ioprio class for cgroup. In this way, we can ensure that the real-time tasks of a cgroup can be scheduled in time. Similarly, the processing of offline task groups can also be simpler. The bfq.ioprio interface now is available for cgroup v1 and cgroup v2. Users can configure the ioprio for cgroup through this interface, as shown below: echo "1 2"> blkio.bfq.ioprio The above two values respectively represent the values of ioprio class and ioprio for cgroup. The ioprio of tasks within the cgroup is uniformly equal to the ioprio of the cgroup. If the ioprio of the cgroup is disabled, the ioprio of the task remains the same, usually from io_context. When testing, using fio and fio_generate_plots we can clearly see that the IO delay of the task satisfies RT> BE> IDLE. When RT is running, BE and IDLE are guaranteed minimum bandwidth. When used with bfq.weight, we can also isolate the resource within the same class. The test process is as follows: # prepare data disk mount /dev/sdb /data1 # create cgroup v1 hierarchy cd /sys/fs/cgroup/blkio mkdir rt be idle echo "1 0" > rt/blkio.bfq.ioprio echo "2 0" > be/blkio.bfq.ioprio echo "3 0" > idle/blkio.bfq.ioprio # run fio test fio fio.ini # generate svg graph fio_generate_plots res The contents of fio.ini are as follows: [global] ioengine=libaio group_reporting=1 log_avg_msec=500 direct=1 time_based=1 iodepth=16 size=100M rw=write bs=1M [rt] name=rt write_bw_log=rt write_lat_log=rt write_iops_log=rt filename=/data1/rt.bin cgroup=rt runtime=30s nice=-10 [be] name=be new_group write_bw_log=be write_lat_log=be write_iops_log=be filename=/data1/be.bin cgroup=be runtime=60s [idle] name=idle new_group write_bw_log=idle write_lat_log=idle write_iops_log=idle filename=/data1/idle.bin cgroup=idle runtime=90s V2: 1. Optmise bfq_select_next_class(). 2. Introduce bfq_group [] to track the number of groups for each CLASS. 3. Optimse IO injection, EMQ and Idle mechanism for CLASS_RT. Chunguang Xu (11): bfq: introduce bfq_entity_to_bfqg helper method bfq: limit the IO depth of idle_class to 1 bfq: keep the minimun bandwidth for be_class bfq: expire other class if CLASS_RT is waiting bfq: optimse IO injection for CLASS_RT bfq: disallow idle if CLASS_RT waiting for service bfq: disallow merge CLASS_RT with other class bfq: introduce bfq.ioprio for cgroup bfq: convert the type of bfq_group.bfqd to bfq_data* bfq: remove unnecessary initialization logic bfq: optimize the calculation of bfq_weight_to_ioprio() block/bfq-cgroup.c | 99 +++++++++++++++++++++++++++++++---- block/bfq-iosched.c | 47 ++++++++++++++--- block/bfq-iosched.h | 28 ++++++++-- block/bfq-wf2q.c | 124 +++++++++++++++++++++++++++++++++----------- 4 files changed, 244 insertions(+), 54 deletions(-) -- 2.30.0
