Re: Git Scaling: What factors most affect Git performance for a large repo?

[Junio C Hamano <gitster@pobox.com>]

Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:

> On Fri, Feb 20, 2015 at 10:04 PM, Junio C Hamano <gitster@pobox.com> wrote:
>> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
>>
>>> I actually ran this a few times while testing it, so this is a before
>>> and after on a hot cache of linux.git with 406 tags v.s. ~140k. I ran
>>> the gc + repack + bitmaps for both repos noted in an earlier reply of
>>> mine, and took the fastest run out of 3:
>>>
>>>     $ time (git log master -100 >/dev/null)
>>>     Before: real    0m0.021s
>>>     After: real    0m2.929s
>>
>> Do you force --decorate with some config?  Or do you see similar
>> performance difference with "git rev-parse master", too?
>
> Yes, I had log.decorate=short set in my config. With --no-decorate:
>
>     $ time (git log --no-decorate -100 >/dev/null)
>     # Before: real    0m0.010s
>     # After: real    0m0.065s

There you have the answer to your earlier question, then, which was:

>> tl;dr: After some more testing it turns out the performance issues we
>> have are almost entirely due to the number of refs. Some of these I
>> knew about and were obvious (e..g. git pull), but some aren't so
>> obvious (why does "git log" without "--all" slow down as a function of
>> the overall number of refs?).