[darcs-users] no more checkpoints, but hashed repos for GHC in Darcs 2.4?

Simon Marlow simonmar at microsoft.com
Mon Sep 14 08:43:24 UTC 2009

> -----Original Message-----
> From: Eric Kow [mailto:eric.kow at gmail.com] On Behalf Of Eric Kow
> Sent: 13 September 2009 23:25
> To: darcs-users at darcs.net; Simon Marlow
> Subject: no more checkpoints, but hashed repos for GHC in Darcs 2.4?
> On Sun, Sep 13, 2009 at 11:15:27 +0100, Ian Lynagh wrote:
> > That's going to be an obstacle to us upgrading darcs on
> > darcs.haskell.org. Currently we rely on periodic checkpointing of repos
> > to keep down the amount of data that GHC buildbots download.
> If this is acceptable to you folks: let's see how this hashed-storage
> stuff goes.  My hope is that we can make hashed repositories acceptable
> for use by the GHC team and the rest of the darcs user community.  If
> so, the GHC buildbot could just use --lazy instead of downloading
> checkpoint patches.
> Would this be OK for the GHC team?

This is fine by me.  But we need to work with you folks to make sure that hashed repos are not a regression for us before we're forced to switch.  That means fixing at least

  - http://bugs.darcs.net/issue1582 (permission denied on Windows,
    perhaps already fixed in hashed-storage, I need to check)

  - http://bugs.darcs.net/issue1589 (7-second overhead for pulling
    or unpulling one patch)

  - timestamps getting out of sync by hard-linking the hashed pristine files.
    I presume this is fixed by darcs-hs anyway.

  - dividing the cache into subdirectories to avoid bad filesystem
    performance with large directories.

Right now I'm using darcs 2.2 with darcs-1 repos at work, and I'm pretty happy with it.  On my laptop I'm using darcs 2.3 with hashed repos, and while some things are blindingly fast (whatsnew), some other things are grotesquely slow :-(


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