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Re: [PATCH 4/4] gc --aggressive: three phase repacking

From
Jeff King <peff@peff.net>
Date
Mar 18, 2014, 05:13 UTC
Message-ID
<20140318051342.GA17200@sigill.intra.peff.net>
In-Reply-To
<CACsJy8CU3JyL74OuurjDr5-FHmBOCRahtXukukCqGx1cTdjvMQ@mail.gmail.com>
On Tue, Mar 18, 2014 at 12:00:48PM +0700, Duy Nguyen wrote:
Show 19 quoted lines
> On Tue, Mar 18, 2014 at 11:50 AM, Jeff King <peff@peff.net> wrote:
> > On Sun, Mar 16, 2014 at 08:35:04PM +0700, Nguyễn Thái Ngọc Duy wrote:
> >
> >> As explained in the previous commit, current aggressive settings
> >> --depth=250 --window=250 could slow down repository access
> >> significantly. Notice that people usually work on recent history only,
> >> we could keep recent history more loosely packed, so that repo access
> >> is fast most of the time while the pack file remains small.
> >
> > One thing I have not seen is real-world timings showing the slowdown
> > based on --depth. Did I miss them, or are we just making assumptions
> > based on one old case from 2009 (that, AFAIK does not have real numbers,
> > just speculation)? Has anyone measured the effect of bumping the delta
> > cache size (and its hash implementation)?
> 
> David tested it with git-blame [1]. I should probably run some tests
> too (I don't remember if I tested some operations last time).
> 
> http://thread.gmane.org/gmane.comp.version-control.git/242277/focus=242435
Ah, thanks. I do remember that thread now.

It looks like David's last word is that he gets a significant performance from bumping the delta base cache size (and number of buckets). And that matches the timings I just did. I suspect there are still pathological cases that could behave worse, but it really sounds like we should be looking into improving that cache as a first step.

-Peff
Previous: Duy NguyenNext: David Kastrup
Message 12 of 21 in “Better "gc --aggressive"”
  1. 0/4 Better "gc --aggressive"Nguyễn Thái Ngọc Duy, Mar 16, 2014
  2. 1/4 environment.c: fix constness for odb_pack_keep()Nguyễn Thái Ngọc Duy, Mar 16, 2014
  3. index-pack: do not segfault when keep_name is NULLNguyễn Thái Ngọc Duy, Mar 16, 2014
  4. 2/4 pack-objects: support --keepNguyễn Thái Ngọc Duy, Mar 16, 2014
  5. 3/4 gc --aggressive: make --depth configurableNguyễn Thái Ngọc Duy, Mar 16, 2014
  6. 4/4 gc --aggressive: three phase repackingNguyễn Thái Ngọc Duy, Mar 16, 2014
  7. Junio C HamanoMar 17, 2014
  8. Duy NguyenMar 17, 2014
  9. Junio C HamanoMar 17, 2014
  10. Jeff KingMar 18, 2014
  11. Duy NguyenMar 18, 2014
  12. Jeff KingMar 18, 2014
  13. David KastrupMar 18, 2014
  14. Duy NguyenMar 19, 2014
  15. Jeff KingMar 18, 2014
  16. Duy NguyenMar 18, 2014
  17. Duy NguyenMar 18, 2014
  18. David KastrupMar 18, 2014
  19. David KastrupMar 18, 2014
  20. Duy NguyenMar 16, 2014
  21. Duy NguyenMar 20, 2014

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