Hi, at last, here is my first patch series meant for merging. It adds BFQ to blk-mq. Don't worry, in this message I won't bore you again with the wonderful properties of BFQ :) A quick update on the status of the code: thanks to Murphy's laws, in the last handful of days, 1) A kind of rare failure, reported only once by a user, several months ago, has been reported again. Fortunately, the bug reporter provided an oops this time. 2) An unexpected bandwidth unbalance between greedy reads and writes has been noted. I have chosen however to submit these patches before attacking these new problems. Let me also recall the limitations of the current version of BFQ. On average CPUs, it can handle, without loss of throughput or fairness guarantees, devices performing at most ~30K IOPS; at most ~50 KIOPS on faster CPUs. Just to put this into context, these are about the same limits as CFQ in blk. A second intrinsic problem is the current need for device idling when differentiated bandwidth distribution must be guaranteed. Over the last months, I have seen that, fortunately, there is room for significant improvements with both these limitations. I plan to work on these improvements after we are done (and if everything goes well) with merging BFQ. Finally, a few details on the patchset. The first two patches introduce BFQ-v0, which is more or less the first version of BFQ submitted a few years ago [1]. The remaining patches turn progressively BFQ-v0 into BFQ-v8r8, the current version of BFQ. Some patch generates WARNINGS with checkpatch.pl, but these WARNINGS seem to be either unavoidable for the involved pieces of code (which the patch just extends), or false positives. Thanks, Paolo [1] https://lkml.org/lkml/2008/4/1/234 Arianna Avanzini (4): block, bfq: add full hierarchical scheduling and cgroups support block, bfq: add Early Queue Merge (EQM) block, bfq: reduce idling only in symmetric scenarios block, bfq: handle bursts of queue activations Paolo Valente (10): block, bfq: introduce the BFQ-v0 I/O scheduler as an extra scheduler block, bfq: improve throughput boosting block, bfq: modify the peak-rate estimator block, bfq: add more fairness with writes and slow processes block, bfq: improve responsiveness block, bfq: reduce I/O latency for soft real-time applications block, bfq: preserve a low latency also with NCQ-capable drives block, bfq: reduce latency during request-pool saturation block, bfq: boost the throughput on NCQ-capable flash-based devices block, bfq: boost the throughput with random I/O on NCQ-capable HDDs Documentation/block/00-INDEX | 2 + Documentation/block/bfq-iosched.txt | 530 +++ block/Kconfig.iosched | 21 + block/Makefile | 1 + block/bfq-iosched.c | 8751 +++++++++++++++++++++++++++++++++++ block/elevator.c | 16 +- include/linux/blkdev.h | 2 +- 7 files changed, 9317 insertions(+), 6 deletions(-) create mode 100644 Documentation/block/bfq-iosched.txt create mode 100644 block/bfq-iosched.c -- 2.10.0
