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Re: RFC: adding xdelta compression to git

From
Linus Torvalds <torvalds@osdl.org>
Date
May 3, 2005, 17:35 UTC
Message-ID
<Pine.LNX.4.58.0505031031240.3594@ppc970.osdl.org>
In-Reply-To
<Pine.LNX.4.61.0505031151380.32767@cag.csail.mit.edu>
On Tue, 3 May 2005, C. Scott Ananian wrote:
> 
> Linus knows this.  His point is just to be sure you actually *code* that 
> walk in fsck, and (hopefully) do so w/o complicating the fsck too much.
Indeed. It's also a performance issue.

If you do xdelta objects, and don't tell fsck about it, then fsck will just check every object as a blob. Why is that bad?

Think about it: let's say that you have a series of xdelta objects, and a fsck that is xdelta-unaware. It will unpack each object independently, which means that it will keep on doing the same early xdelta work over and over and over again. Instead of just applying them in order, and checking the sha1 of the result at each point.

Now, You probably want to limit the length of the chains to some firly small number anyway, so maybe that's not a big deal. Who knows. And I'm actually still so anal that I don't think I'd use this for _my_ tree, just because I'm a worry-wart (and I still think disk is incredibly cheap ;)

		Linus
Previous: C. Scott AnanianNext: Davide Libenzi
Message 6 of 32 in “RFC: adding xdelta compression to git”
  1. Alon ZivMay 3, 2005
  2. Nicolas PitreMay 3, 2005
  3. Linus TorvaldsMay 3, 2005
  4. Davide LibenziMay 3, 2005
  5. C. Scott AnanianMay 3, 2005
  6. Linus TorvaldsMay 3, 2005
  7. Davide LibenziMay 3, 2005
  8. add the ability to create and retrieve delta objectsNicolas Pitre, May 3, 2005
  9. Chris MasonMay 3, 2005
  10. Nicolas PitreMay 3, 2005
  11. Linus TorvaldsMay 3, 2005
  12. Chris MasonMay 3, 2005
  13. C. Scott AnanianMay 3, 2005
  14. Chris MasonMay 3, 2005
  15. Chris MasonMay 3, 2005
  16. Nicolas PitreMay 3, 2005
  17. Chris MasonMay 3, 2005
  18. Nicolas PitreMay 3, 2005
  19. Chris MasonMay 3, 2005
  20. Linus TorvaldsMay 3, 2005
  21. add the ability to create and retrieve delta objectsNicolas Pitre, May 3, 2005
  22. Chris MasonMay 4, 2005
  23. C. Scott AnanianMay 4, 2005
  24. Chris MasonMay 4, 2005
  25. Linus TorvaldsMay 4, 2005
  26. Chris MasonMay 4, 2005
  27. Nicolas PitreMay 5, 2005
  28. Geert BoschMay 4, 2005
  29. Chris MasonMay 4, 2005
  30. Nicolas PitreMay 5, 2005
  31. Dan HolmsandMay 3, 2005
  32. C. Scott AnanianMay 3, 2005

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