From: Paolo Valente <paolo.valente@xxxxxxxxxx> [Re-posting, previous attempt seems to have partially failed] Hi, this patchset introduces the last version of BFQ, a proportional-share storage-I/O scheduler. BFQ also supports hierarchical scheduling with a cgroups interface. The first version of BFQ was submitted a few years ago [1]. It is denoted as v0 in the patches, to distinguish it from the version I am submitting now, v7r4. In particular, the first four patches introduce BFQ-v0, whereas the remaining patches turn it progressively into BFQ-v7r4. Here are some nice features of this last version. Low latency for interactive applications According to our results, regardless of the actual background workload, for interactive tasks the storage device is virtually as responsive as if it was idle. For example, even if one or more of the following background workloads are being executed: - one or more large files are being read or written, - a tree of source files is being compiled, - one or more virtual machines are performing I/O, - a software update is in progress, - indexing daemons are scanning filesystems and updating their databases, starting an application or loading a file from within an application takes about the same time as if the storage device was idle. As a comparison, with CFQ, NOOP or DEADLINE, and in the same conditions, applications experience high latencies, or even become unresponsive until the background workload terminates (also on SSDs). Low latency for soft real-time applications Also soft real-time applications, such as audio and video players/streamers, enjoy low latency and drop rate, regardless of the storage-device background workload. As a consequence, these applications do not suffer from almost any glitch due to the background workload. High throughput On hard disks, BFQ achieves up to 30% higher throughput than CFQ, and up to 150% higher throughput than DEADLINE and NOOP, with half of the parallel workloads considered in our tests. With the rest of the workloads, and with all the workloads on flash-based devices, BFQ achieves instead about the same throughput as the other schedulers. Strong fairness guarantees (already provided by BFQ-v0) As for long-term guarantees, BFQ distributes the device throughput (and not just the device time) as desired to I/O-bound applications, with any workload and regardless of the device parameters. What allows BFQ to provide the above features is its accurate scheduling engine (patches 1-4), combined with a set of simple heuristics and improvements (patches 5-14). A 15-minute demo of the performance of BFQ is available here [2]. I made this demo with an older version of BFQ (v3r4) and under Linux 3.4.0. We have further improved BFQ since then. The performance of the last version of BFQ is shown, e.g., through some graphs here [3], under 3.14.0, compared against CFQ, DEADLINE and NOOP, and on: a fast and a slow hard disk, a RAID1, an SSD, a microSDHC Card and an eMMC. As an example, our results on the SSD are reported also in a table at the end of this email. Finally, details on how BFQ and its components work are provided in the descriptions of the patches. An organic description of the main BFQ algorithm and of most of its features can instead be found in this paper [4]. Finally, as for testing in everyday use, BFQ is the default I/O scheduler in, e.g., Manjaro, Sabayon, OpenMandriva and Arch Linux ARM in some NAS boxes, plus several kernel forks for PCs and smartphones. BFQ is instead optionally available in, e.g., Arch, PCLinuxOS and Gentoo. In addition, we record a few tens of downloads per day from people using other distributions. The feedback received so far basically confirms the expected latency drop and throughput boost. Paolo Results on a Plextor PX-256M5S SSD The first two rows of the next table report the aggregate throughput achieved by BFQ, CFQ, DEADLINE and NOOP, while ten parallel processes read, either sequentially or randomly, a separate portion of the memory blocks each. These processes read directly from the device, and no process performs writes, to avoid writing large files repeatedly and wearing out the SSD during the many tests done. As can be seen, all schedulers achieve about the same throughput with sequential readers, whereas, with random readers, the throughput slightly grows as the complexity, and hence the execution time, of the schedulers decreases. In fact, with random readers, the number of IOPS is extremely higher, and all CPUs spend all the time either executing instructions or waiting for I/O (the total idle percentage is 0). Therefore, the processing time of I/O requests influences the maximum throughput achievable. The remaining rows report the cold-cache start-up time experienced by various applications while one of the above two workloads is being executed in parallel. In particular, "Start-up time 10 seq/rand" stands for "Start-up time of the application at hand while 10 sequential/random readers are running". A timeout fires, and the test is aborted, if the application does not start within 60 seconds; so, in the table, '>60' means that the application did not start before the timeout fired. With sequential readers, the performance gap between BFQ and the other schedulers is remarkable. Background workloads are intentionally very heavy, to show the performance of the schedulers in somewhat extreme conditions. Differences are however still significant also with lighter workloads, as shown, e.g., here [3] for slower devices. ----------------------------------------------------------------------------- | SCHEDULER | Test | ----------------------------------------------------------------------------- | BFQ | CFQ | DEADLINE | NOOP | | ----------------------------------------------------------------------------- | | | | | Aggregate Throughput | | | | | | [MB/s] | | 399 | 400 | 400 | 400 | 10 raw seq. readers | | 191 | 193 | 202 | 203 | 10 raw random readers | ----------------------------------------------------------------------------- | | | | | Start-up time 10 seq | | | | | | [sec] | | 0.21 | >60 | 1.91 | 1.88 | xterm | | 0.93 | >60 | 10.2 | 10.8 | oowriter | | 0.89 | >60 | 29.7 | 30.0 | konsole | ----------------------------------------------------------------------------- | | | | | Start-up time 10 rand | | | | | | [sec] | | 0.20 | 0.30 | 0.21 | 0.21 | xterm | | 0.81 | 3.28 | 0.80 | 0.81 | oowriter | | 0.88 | 2.90 | 1.02 | 1.00 | konsole | ----------------------------------------------------------------------------- [1] https://lkml.org/lkml/2008/4/1/234 https://lkml.org/lkml/2008/11/11/148 [2] http://youtu.be/J-e7LnJblm8 [3] http://www.algogroup.unimo.it/people/paolo/disk_sched/results.php [4] P. Valente and M. Andreolini, "Improving Application Responsiveness with the BFQ Disk I/O Scheduler", Proceedings of the 5th Annual International Systems and Storage Conference (SYSTOR '12), June 2012. Slightly extended version: http://www.algogroup.unimo.it/people/paolo/disk_sched/bf1-v1-suite-results.pdf Arianna Avanzini (1): block, bfq: add Early Queue Merge (EQM) Fabio Checconi (4): block: kconfig update and build bits for BFQ block: introduce the BFQ-v0 I/O scheduler block: add hierarchical-support option to kconfig block, bfq: add full hierarchical scheduling and cgroups support Paolo Valente (9): block, bfq: improve throughput boosting block, bfq: modify the peak-rate estimator block, bfq: add more fairness to boost throughput and reduce latency 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 block/Kconfig.iosched | 32 + block/Makefile | 1 + block/bfq-cgroup.c | 909 ++++++++++ block/bfq-ioc.c | 36 + block/bfq-iosched.c | 3802 +++++++++++++++++++++++++++++++++++++++++ block/bfq-sched.c | 1104 ++++++++++++ block/bfq.h | 729 ++++++++ include/linux/cgroup_subsys.h | 4 + 8 files changed, 6617 insertions(+) create mode 100644 block/bfq-cgroup.c create mode 100644 block/bfq-ioc.c create mode 100644 block/bfq-iosched.c create mode 100644 block/bfq-sched.c create mode 100644 block/bfq.h -- 1.9.2 _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers