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Re: Speeding up dpkg, a proposal

On Thu, Mar 03, 2011 at 01:51:35AM +0800, Chow Loong Jin wrote:
> Hi,
> On Thursday 03,March,2011 12:02 AM, Marius Vollmer wrote:
> > [...]
> > - Instead, we move all packages that are to be unpacked into
> >   half-installed / reinstreq before touching the first one, and put a
> >   big sync() right before carefully writing /var/lib/dpkg/status.
> Could we somehow avoid using sync()? sync() syncs all mounted filesystems,
> which isn't exactly very friendly when you have a few slow-syncing
> filesystems like btrfs (or even NFS) mounted. I recall my schroots that ran
> on tmpfs unpacking exceptionally slowly due to this issue until I stuck
> libeatmydata (or a variant of it) onto the schroots' dpkgs.

Btrfs is quite simply awful in chroots at present, and it seems
--force-unsafe-io doesn't really seem to help massively either.
It's dog slow--it's quicker to untar a chroot onto ext3 than to
bother with Btrfs.

This is a shame, because Btrfs snapshots are the most fast and
reliable out there at the moment (LVM snapshots are fast, but not
/that/ fast, and LVM appears to have locking issues which need
addressing to make it robust enough to handle simultaneous
creation and removal of many snapshots.

It would be great if there was a solution to this problem; is anyone
running Btrfs as a root filesystem who has any suggestions?


  .''`.  Roger Leigh
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