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

From: Piotr Krukowiecki <piotr.krukowiecki@gmail.com>
Date: Feb 15, 2012, 08:57 UTC
Message-ID: <CAA01Cso_8=159UDMFUHiYz1X=gYtpbqRO4h3TMw7N=4YMV8YNg@mail.gmail.com>
In-Reply-To: <8762f9k5sg.fsf@thomas.inf.ethz.ch>

On Tue, Feb 14, 2012 at 12:34 PM, Thomas Rast <trast@inf.ethz.ch> wrote:

Show 33 quoted lines

> Piotr Krukowiecki <piotr.krukowiecki@gmail.com> writes:
>
>> On Fri, Feb 10, 2012 at 10:42 AM, Piotr Krukowiecki
>> <piotr.krukowiecki@gmail.com> wrote:
>>> 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
> [...]
>> 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