On Thu, May 09, 2024 at 04:43:21PM -0400, John Meneghini wrote: > I'm re-issuing Hannes's latency patches in preparation for LSFMM Hello John, Just a small note. Please don't reply-to the previous version of the series (v2), when sending out a v3. It creates "an unmanageable forest of references in email clients". See: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#explicit-in-reply-to-headers Instead just add the url to the v2 on lore.kernel.org. See you at LSFMM! Kind regards, Niklas > > Changes since V2: > > I've done quite a bit of work cleaning up these patches. There were a > number of checkpatch.pl problems as well as some compile time errors > when config BLK_NODE_LATENCY was turned off. After the clean up I > rebased these patches onto Ewan's "nvme: queue-depth multipath iopolicy" > patches. This allowed me to test both iopolicy changes together. > > All of my test results, together with the scripts I used to generate these > graphs, are available at: > > https://github.com/johnmeneghini/iopolicy > > Please use the scripts in this repository to do your own testing. > > Changes since V1: > > Hi all, > > there had been several attempts to implement a latency-based I/O > scheduler for native nvme multipath, all of which had its issues. > > So time to start afresh, this time using the QoS framework > already present in the block layer. > It consists of two parts: > - a new 'blk-nlatency' QoS module, which is just a simple per-node > latency tracker > - a 'latency' nvme I/O policy > > Using the 'tiobench' fio script with 512 byte blocksize I'm getting > the following latencies (in usecs) as a baseline: > - seq write: avg 186 stddev 331 > - rand write: avg 4598 stddev 7903 > - seq read: avg 149 stddev 65 > - rand read: avg 150 stddev 68 > > Enabling the 'latency' iopolicy: > - seq write: avg 178 stddev 113 > - rand write: avg 3427 stddev 6703 > - seq read: avg 140 stddev 59 > - rand read: avg 141 stddev 58 > > Setting the 'decay' parameter to 10: > - seq write: avg 182 stddev 65 > - rand write: avg 2619 stddev 5894 > - seq read: avg 142 stddev 57 > - rand read: avg 140 stddev 57 > > That's on a 32G FC testbed running against a brd target, > fio running with 48 threads. So promises are met: latency > goes down, and we're even able to control the standard > deviation via the 'decay' parameter. > > As usual, comments and reviews are welcome. > > Changes to the original version: > - split the rqos debugfs entries > - Modify commit message to indicate latency > - rename to blk-nlatency > > Hannes Reinecke (2): > block: track per-node I/O latency > nvme: add 'latency' iopolicy > > John Meneghini (1): > nvme: multipath: pr_notice when iopolicy changes > > MAINTAINERS | 1 + > block/Kconfig | 9 + > block/Makefile | 1 + > block/blk-mq-debugfs.c | 2 + > block/blk-nlatency.c | 389 ++++++++++++++++++++++++++++++++++ > block/blk-rq-qos.h | 6 + > drivers/nvme/host/multipath.c | 73 ++++++- > drivers/nvme/host/nvme.h | 1 + > include/linux/blk-mq.h | 11 + > 9 files changed, 484 insertions(+), 9 deletions(-) > create mode 100644 block/blk-nlatency.c > > -- > 2.39.3 > >
