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List:       fedora-devel-list
Subject:    Re: Has something changed with RPMS?
From:       "Richard W.M. Jones" <rjones () redhat ! com>
Date:       2020-06-02 17:26:57
Message-ID: 20200602172657.GK15536 () redhat ! com
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On Tue, Jun 02, 2020 at 12:44:17PM +0200, Florian Weimer wrote:
> * Panu Matilainen:
> 
> > Lets start with the basics:
> > - is sqlite even involved - it will only be used on rawhide builds if
> > mock bootstrap is used
> > - does it make a difference if you override _db_backend to bdb/sqlite
> > from mock config / cli define
> > - a reproducer please (eg, what package is considerably slower to
> > build than before, and by how much)
> 
> And: Does the difference reproduce when building on tmpfs?

Good time to say that you can use an NBD loopback to mock-build either
on a userspace ramdisk or backed by a disk but discarding flush
requests.  The performance is indistinguishable from tmpfs (and much
more flexible in other ways).  I did some benchmarking a couple of
weeks ago:

  https://www.redhat.com/archives/libguestfs/2020-May/msg00053.html
  https://www.redhat.com/archives/libguestfs/2020-May/msg00074.html

Easy set up is:

  # rm -f /tmp/sock
  # nbdkit -U /tmp/sock memory 100G
  # nbd-client -b 512 -unix /tmp/sock /dev/nbd0 -connections 4
  # mkfs.xfs /dev/nbd0
  # mount /dev/nbd0 /var/lib/mock

or using http://libguestfs.org/nbdkit-tmpdisk-plugin.1.html:

  # rm -f /tmp/sock
  # nbdkit -U /tmp/sock tmpdisk size=100G
  # nbd-client -b 512 -unix /tmp/sock /dev/nbd0 -connections 1
  # mount /dev/nbd0 /var/lib/mock

or (requires bleeding edge nbdkit):

  # rm -f /tmp/sock
  # lvcreate -L 100G -n tmp /dev/fedora
  # nbdkit -U /tmp/socket --filter=fua fuamode=discard file /dev/fedora/tmp
  # nbd-client -b 512 -unix /tmp/sock /dev/nbd0 -connections 4
  # mkfs.xfs /dev/nbd0
  # mount /dev/nbd0 /var/lib/mock

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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