Re: Index files autocompletion too slow in big repositories (w / suggestion for improvement)
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Apr 17, 2017, 04:05 UTC
- Message-ID
- <xmqqefwrk7ao.fsf@gitster.mtv.corp.google.com>
- In-Reply-To
- <7a07a2a8-07a6-4342-80d0-7684e6242326@kdbg.org>
Johannes Sixt <j6t@kdbg.org> writes:
Show 37 quoted lines
> Cc Gábor.
>
> Am 15.04.2017 um 00:33 schrieb Ævar Arnfjörð Bjarmason:
>> On Sat, Apr 15, 2017 at 12:08 AM, Carlos Pita <carlosjosepita@gmail.com> wrote:
>>> This is much faster (below 0.1s):
>>>
>>> __git_index_files ()
>>> {
>>> local dir="$(__gitdir)" root="${2-.}" file;
>>> if [ -d "$dir" ]; then
>>> __git_ls_files_helper "$root" "$1" | \
>>> sed -r 's@/.*@@' | uniq | sort | uniq
>>> fi
>>> }
>>>
>>> time __git_index_files
>>>
>>> real 0m0.075s
>>> user 0m0.083s
>>> sys 0m0.010s
>>>
>>> Most of the improvement is due to the simpler, non-grouping, regex.
>>> Since I expect most of the common prefixes to arrive consecutively,
>>> running uniq before sort also improves things a bit. I'm not removing
>>> leading double quotes anymore (this isn't being done by the current
>>> version, anyway) but this doesn't seem to hurt.
>>>
>>> Despite the dependence on sed this is ten times faster than the
>>> original, maybe an option to enable fast index completion or something
>>> like that might be desirable.
>>
>> It's fine to depend on sed, these shell-scripts are POSIX compatible,
>> and so is sed, we use sed in a lot of the built-in shellscripts.
>
> This is about command line completion. We go a long way to avoid
> forking processes there. What is 10x faster on Linux despite of
> forking a process may not be so on Windows.Doesn't this depend on how many paths there are? If there are only a few paths, the loop in shell would beat a pipe into sed even on Linux, I suspect, and if there are tons of paths, at some number, loop in shell would become slower than a single spawning of sed on platforms with slower fork, no?