Re: git status: small difference between stating whole repository and small subdirectory

On Tue, Feb 14, 2012 at 12:34 PM, Thomas Rast [off-list ref] wrote:

Piotr Krukowiecki [off-list ref] writes:

quoted

On Fri, Feb 10, 2012 at 10:42 AM, Piotr Krukowiecki
[off-list ref] wrote:

quoted

I compared stating whole tree vs one small subdirectory, and I
expected that for the subdirectory status will be very very fast.
After all, it has only few files to stat. But it's not fast. Why?


With cold cache (echo 3 | sudo tee /proc/sys/vm/drop_caches):

$ time git status    > /dev/null
real    0m41.670s
user    0m0.980s
sys     0m2.908s

$ time git status -- src/.../somedir   > /dev/null
real    0m17.380s
user    0m0.748s
sys     0m0.328s

[...]

quoted

I can't reproduce this behavior at the moment. 'status' on the
directory takes about 1.5s instead of 17s. status on whole repository
takes 27s.
This is my work repository, so it was changed today.

To me these timings smell like a combination of either a network
filesystem or a slow/busy disk, and non-packed repositories.  Next time
this happens look at 'git count-objects', run 'git gc' and redo the
timings.

If you are indeed on a network filesystem, also look at the
core.preloadIndex setting.

All is on local disk and system is idle.

Indeed, after gc the times went down:
10s -> 2.3s (subdirectory)
17s -> 9.5s (whole repo)

2 seconds is much better and I'd say acceptable for me. But my questions are:
- why is it so slow with not packed repo?
- can it be faster without repacking?
- even with packed repo, the time on small subdirectory is much higher
than I'd expect given time on whole repo and subdirectory size - why?


$ git count-objects -v
count: 5095
size: 37084
in-pack: 755364
packs: 21
size-pack: 2398468
prune-packable: 0
garbage: 0

$ git gc
Counting objects: 760212, done.
Compressing objects: 100% (158651/158651), done.
Writing objects: 100% (760212/760212), done.
Total 760212 (delta 535848), reused 736108 (delta 513257)
Checking connectivity: 760212, done.

$ time git status  -- .
real	0m2.503s
user	0m0.160s
sys	0m0.096s

$ time git status
real	0m9.663s
user	0m0.232s
sys	0m0.556s


-- 
Piotr Krukowiecki