On Wed, Jul 23, 2008 at 07:09:20PM +0000, Pierre Habouzit wrote:
> On Wed, Jul 23, 2008 at 05:59:01PM +0000, Linus Torvalds wrote:
> > In fact, the two top entries in a profile look roughly like:
> >
> > 102161 70.2727 libz.so.1.2.3 libz.so.1.2.3 (no symbols)
> > 7685 5.2862 git git find_pack_entry_one
> > ...
> >
> > ie 70% of the time is just purely unpacking the data, and another 5% is
> > just finding it. We could perhaps improve on it, but not a whole lot.
>
> Well there is an easy way though, that could reduce that: using
> adaptative compression. I proposed a patch once upon a time, that set
> the compression strengh to 0 for "small" objects with a configurable
> cut-off. If you do that, most trees, commits messages and so on aren't
> compressed, and it will reduce (with IIRC a 5-liner) this time quite
> dramatically.
>
> I could maybe resurect it to see if for people that do the kind of
> things Ingo does it helps. By setting the cut-off at 1k, I had packs
> being less than 1% bigger IIRC. I'll try to find it again and run your
> tests with it to see how much it helps.
Unsurprisingly with a 1024o cutoff, the numbers are (first run is
forced cold-cache with /proc/.../drop_caches, second is the best run of 5):
default git:
3.10user 0.16system 0:08.10elapsed 40%CPU (0avgtext+0avgdata 0maxresident)k
116152inputs+0outputs (671major+35286minor)pagefaults 0swaps
2.01user 0.11system 0:02.12elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+35958minor)pagefaults 0swaps
With a 1024k cutoff:
1.16user 0.13system 0:08.29elapsed 15%CPU (0avgtext+0avgdata 0maxresident)k
154208inputs+0outputs (947major+39777minor)pagefaults 0swaps
0.76user 0.06system 0:00.82elapsed 100%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+40724minor)pagefaults 0swaps
According to [0], a 1k cutoff meant something like a 10% larger pack. 512o
meant an almost identical pack in size, but with reduced performance
improvements.
[0] http://thread.gmane.org/gmane.comp.version-control.git/70019/focus=70250
--
·O· Pierre Habouzit
··O madcoder@xxxxxxxxxx
OOO http://www.madism.org
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