Hi Jens,
A feature that is missing from the Linux kernel for storage devices that
support I/O priorities is to set the I/O priority in requests involving page
cache writeback. Since the identity of the process that triggers page cache
writeback is not known in the writeback code, the priority set by ioprio_set()
is ignored. However, an I/O cgroup is associated with writeback requests
by certain filesystems. Hence this patch series that implements the following
changes:
* Add an rq-qos policy that makes the I/O priority configurable per I/O cgroup
and also that changes the I/O priority of requests to the lower of (request
I/O priority, cgroup I/O priority).
* Introduce one queue per I/O priority in the mq-deadline scheduler.
* Dispatch the highest priority requests first.
Please consider this patch series for kernel v5.14.
Thanks,
Bart.
Changes compared to v2:
- For the blk-ioprio rq-qos policy, switched from numeric to textual policy
names.
- Moved rq_qos_id_to_name() into debugfs code.
- Moved the mq-deadline I/O statistics into io.stat.
- Introduced the dd_per_prio data structure.
- Switched from a single sort list to one sort list per I/O priority.
- Removed the WARN_ON_ONCE(blkcg == NULL) statements.
Changes compared to v1:
- Moved the code for assigning an I/O priority into a new rq-qos policy.
- Dropped patch "block/mq-deadline: Reduce the read expiry time for
non-rotational media".
- Made sure that dd->async_depth >= 1.
- Implemented an aging mechanism such that lower priority requests are not
postponed forever.
Bart Van Assche (16):
block/Kconfig: Make the BLK_WBT and BLK_WBT_MQ entries consecutive
block/blk-cgroup: Swap the blk_throtl_init() and blk_iolatency_init()
calls
block/blk-rq-qos: Move a function from a header file into a C file
block: Introduce the ioprio rq-qos policy
block/mq-deadline: Add several comments
block/mq-deadline: Add two lockdep_assert_held() statements
block/mq-deadline: Remove two local variables
block/mq-deadline: Rename dd_init_queue() and dd_exit_queue()
block/mq-deadline: Improve compile-time argument checking
block/mq-deadline: Improve the sysfs show and store macros
block/mq-deadline: Reserve 25% of scheduler tags for synchronous
requests
block/mq-deadline: Micro-optimize the batching algorithm
block/mq-deadline: Add I/O priority support
block/mq-deadline: Track I/O statistics
block/mq-deadline: Add cgroup support
block/mq-deadline: Prioritize high-priority requests
Documentation/admin-guide/cgroup-v2.rst | 55 ++
block/Kconfig | 19 +-
block/Kconfig.iosched | 6 +
block/Makefile | 3 +
block/blk-cgroup.c | 14 +-
block/blk-ioprio.c | 262 +++++
block/blk-ioprio.h | 19 +
block/blk-mq-debugfs.c | 15 +
block/blk-rq-qos.h | 14 +-
block/mq-deadline-cgroup.c | 126 +++
block/mq-deadline-cgroup.h | 114 +++
block/mq-deadline-main.c | 1173 +++++++++++++++++++++++
block/mq-deadline.c | 815 ----------------
13 files changed, 1797 insertions(+), 838 deletions(-)
create mode 100644 block/blk-ioprio.c
create mode 100644 block/blk-ioprio.h
create mode 100644 block/mq-deadline-cgroup.c
create mode 100644 block/mq-deadline-cgroup.h
create mode 100644 block/mq-deadline-main.c
delete mode 100644 block/mq-deadline.c
