Il giorno 17 ago 2018, alle ore 19:39, Ricardo Ribalda Delgado =

[off-list ref] ha scritto:

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Hello Paolo
On Fri, Aug 17, 2018 at 7:35 PM Paolo Valente =

[off-list ref] wrote:

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Il giorno 17 ago 2018, alle ore 19:31, Ricardo Ribalda Delgado =

[off-list ref] ha scritto:

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Hello
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Coming from: =

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=3D906328

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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.
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After some debugging, we have figured out that the reason for that
slowness is the Multi-Queue Block IO Queueing Mechanism.
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Debian maintainer has pointed out that in the near future the single
queue will be deprecated.
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My question is if we can get a similar perfomance for bmaptools with
blk-mq and how?
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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)?

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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.
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I could easily enable kyber:
cat /boot/config-4.17.0-1-amd64  | grep CONFIG_MQ_IOSCHED
CONFIG_MQ_IOSCHED_DEADLINE=3Dy
CONFIG_MQ_IOSCHED_KYBER=3Dm
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But I left the card reader on the office, so any test would have to
wait until monday sorry :(
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Try bfq too, as it is probably the one containing also the most old
way heuristics.  If bfq fails too, we will at least know that the issue
is out of the schedulers. Or in every scheduler! :)

Paolo

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Paolo
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Thanks!
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--
Ricardo Ribalda

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Ricardo Ribalda