On 8/17/18 11:39 AM, Ricardo Ribalda Delgado wrote: > Hello Paolo > On Fri, Aug 17, 2018 at 7:35 PM Paolo Valente <paolo.valente@xxxxxxxxxx> wrote: >> >> >> >>> Il giorno 17 ago 2018, alle ore 19:31, Ricardo Ribalda Delgado <ricardo.ribalda@xxxxxxxxx> ha scritto: >>> >>> Hello >>> >>> Coming from: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=906328 >>> >>> bmaptools is kind of a "smart dd" tool, that lets you write images >>> very fast and securely. Since the last Debian Kernel update it has >>> become 5-8 times slower. >>> >>> After some debugging, we have figured out that the reason for that >>> slowness is the Multi-Queue Block IO Queueing Mechanism. >>> >>> Debian maintainer has pointed out that in the near future the single >>> queue will be deprecated. >>> >>> My question is if we can get a similar perfomance for bmaptools with >>> blk-mq and how? >>> >> >> Have you also checked what happens after switching to a different I/O >> scheduler for the involved drive (among none, mq-deadline, bfq and >> kyber)? > > I have only tried mq-deadline and none (because they are enabled by > default on Debian). Both produce results in the same range: 5-8 times > slower. > > I could easily enable kyber: > cat /boot/config-4.17.0-1-amd64 | grep CONFIG_MQ_IOSCHED > CONFIG_MQ_IOSCHED_DEADLINE=y > CONFIG_MQ_IOSCHED_KYBER=m > > But I left the card reader on the office, so any test would have to > wait until monday sorry :( Can someone describe what bmaptools does? IOW, how is it different than dd? Does it use multiple threads for both reads and writes? -- Jens Axboe
