Re: Git benchmarks at OpenOffice.org wiki

[Robin Rosenberg <robin.rosenberg.lists@dewire.com>]

torsdag 03 maj 2007 skrev Johannes Schindelin:
> Hi,
> 
> On Thu, 3 May 2007, Florian Weimer wrote:
> 
> > * Jakub Narebski:
> > 
> > > What I'm really concerned about is branch switch and merging branches, 
> > > when one of the branches is an old one (e.g. unxsplash branch), which 
> > > takes 3min (!) according to the benchmark. 13-25sec for commit is also 
> > > bit long, but BRANCH SWITCHING which takes 3 MINUTES!?
> > 
> > IIRC, GIT accesses every file in the tree, not just the ones that need
> > updating.  How many files were actually updated when you changed
> > branches in your experiment?
> 
> No. Git does not access every file, but rather all stats. That is a huge 
> difference. And it should not take _that_ long for ~64000 files. Granted, 
> it will cause a substantial delay, but not in the range of minutes.

It's worse... On my laptop the switch took ~ten minutes, not three. 
A diff --stat takes over six minutes!! For reference, dd:in the pack 
file with my disk takes ~50 seconds.

The reason is simple. I have a lousy one gigabyte RAM only, while 
git wants 1.7GB virtual to do the diff-stat.  and 800 MB resident. The swap is having a party,

$ vmstat 1
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 1  2 1861632  14108    428 126816   70  347   605   647  594 1041 11  2 74 13
 0  2 1861204  12096    420 125724 3096    8  3096    24  625 1171  5  1  0 94
 0  2 1860896  18972    404 115836 3524  292  3524   292  671 1474  7  4  0 89
 0  2 1860820  18668    364 113736 3556  784  3556   784  669 1384  7  5  0 88
 0  3 1860420  19692    300 109904 3008  180  3156   180  684 1325  8  5  0 87
 0  3 1860184  18560    300 108596 3316  232  3396   232  643 1246  8  4  0 88
 0  2 1859856  21808    292 103744 2108   32  2356    32  637 1319  9  1  0 90

-- robin