Hi Jens On Fri, Aug 17, 2018 at 7:41 PM Jens Axboe <axboe@xxxxxxxxx> wrote: > > 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? https://github.com/intel/bmap-tools/blob/master/bmaptools/BmapCopy.py I am not an author, just a user. But from the code it looks like 1) sets the io scheduler to noop 2) Copy the file in chuncks of block_size (4096 by default) 3) fflush 4) restore io scheduler > > -- > Jens Axboe > -- Ricardo Ribalda
