Hi, this patch series extends BFQ so as to optimize I/O dispatch to multi-actuator drives. In particular, this extension addresses the following issue. Multi-actuator drives appear as a single device to the I/O subsystem [1]. Yet they address commands to different actuators internally, as a function of Logical Block Addressing (LBAs). A given sector is reachable by only one of the actuators. For example, Seagate’s Serial Advanced Technology Attachment (SATA) version contains two actuators and maps the lower half of the SATA LBA space to the lower actuator and the upper half to the upper actuator. Evidently, to fully utilize actuators, no actuator must be left idle or underutilized while there is pending I/O for it. To reach this goal, the block layer must somehow control the load of each actuator individually. This series enriches BFQ with such a per-actuator control, as a first step. Then it also adds a simple mechanism for guaranteeing that actuators with pending I/O are never left idle. See [1] for a more detailed overview of the problem and of the solutions implemented in this patch series. There you will also find some preliminary performance results. Thanks, Paolo [1] https://www.linaro.org/blog/budget-fair-queueing-bfq-linux-io-scheduler-optimizations-for-multi-actuator-sata-hard-drives/ Davide Zini (3): block, bfq: split also async bfq_queues on a per-actuator basis block, bfq: inject I/O to underutilized actuators block, bfq: balance I/O injection among underutilized actuators Federico Gavioli (1): block, bfq: retrieve independent access ranges from request queue Paolo Valente (4): block, bfq: split sync bfq_queues on a per-actuator basis block, bfq: forbid stable merging of queues associated with different actuators block, bfq: turn scalar fields into arrays in bfq_io_cq block, bfq: turn BFQ_NUM_ACTUATORS into BFQ_MAX_ACTUATORS block/bfq-cgroup.c | 97 +++++---- block/bfq-iosched.c | 488 +++++++++++++++++++++++++++++--------------- block/bfq-iosched.h | 149 ++++++++++---- block/bfq-wf2q.c | 2 +- 4 files changed, 493 insertions(+), 243 deletions(-) -- 2.20.1
