The Next Linux Kernel Will Bring More Drivers Converted To Use BLK-MQ I/O
Written by Michael Larabel in Linux Storage on 16 October 2018 at 03:07 PM EDT. 10 Comments
More Linux storage drivers have been converted to the "blk-mq" interfaces for the multi-queue block I/O queuing mechanism for the 4.20~5.0 kernel cycle.

Blk-mq is capable of delivering much better performance with modern storage devices -- namely NVMe PCI Express SSDs but also SCSI drives. This code that's been part of the Linux kernel the past few years allows mapping I/O to multiple queues and distributing the tasks across multiple CPU threads, thus scaling better with today's multi-core servers, while also supporting multiple hardware queues of capable devices.

The key device drivers like NVMe, VirtIO, scsi_mq, and others have already supported the multi-queue block I/O code for quite some time (going back to late Linux 3.x releases) while for the Linux 4.20~5.0 release a number of the smaller drivers are being ported over.

Jens Axboe and Omar Sandoval -- both working for Facebook -- have been converting many of the remaining drivers to using blk-mq. Those latest drivers being ported include sx8, z2ram, gdrom, floppy, ataflop, amiflop, swim3, swim, mtd_blkdevs, xsysace, paride, ps3disk, um, and aoe drivers.

Yes, that's even the original floppy disk driver dating back to Linus Torvalds' code in 1991 now supports the blk-mq interfaces. Within that floppy driver code is a funny original comment from Torvalds still during the kernel's early days: "This file is certainly a mess. I've tried my best to get it working, but I don't like programming floppies, and I have only one anyway."

Converting these mostly older drivers to use blk-mq is generally dozens of lines of code for each driver. The latest activity can be found in linux-block's for-next ahead of the Linux 4.20~5.0 kernel cycle.

With blk-mq being quite fit these days and the remaining drivers getting converted to blk-mq, it will be interesting to see if the legacy I/O interfaces get removed from an upcoming Linux kernel release. This next kernel release is also (re)enabling run-time power management under blk-mq.
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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter or contacted via

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