Hi, On Thursday, September 01, 2016 10:39:46 AM Linus Walleij wrote: > On Thu, Sep 1, 2016 at 12:09 AM, Mark Brown <broo...@kernel.org> wrote: > > > - Do some benchmarks on the current status of the various branches on > > relevant hardware (including trying to convert some of these slower > > devices to blk-mq and seeing what happens). Linus has been working > > on this already in the context of MMC. > > I'm trying to do a patch switching MMC to use blk-mq, so I can > benchmark performance before/after this. > > While we expect mq to perform worse on single-hardware-queue > devices like these, we don't know until we tried, so I'm trying.
I did this (switched MMC to blk-mq) some time ago. Patches are extremely ugly and hacky (basically the whole MMC block layer glue code needs to be re-done) so I'm rather reluctant to sharing them yet (to be honest I would like to rewrite them completely before posting). I only did linear read tests (using dd) so far and results that I got were mixed (BTW the hardware I'm doing this work on is Odroid-XU3). Pure block performance under maximum CPU frequency was slightly worse (5-12%) but the CPU consumption was reduced so when CPU was scaled down manually (or ondemand CPUfreq governor was used) blk-mq mode results were better then vanilla ones (up to 10% when CPU was scaled down to minimum frequency and even up to 50% when using ondemand governor - this finding is very interesting and needs to be investigated further). Best regards, -- Bartlomiej Zolnierkiewicz Samsung R&D Institute Poland Samsung Electronics
