threads / discuss / 29584

Silly Question About Timing

Subject: Silly Question About Timing

## tl;dr

4 messages between Feb 9, 2012 and Feb 9, 2012.

replies: 3people: 3as markdown or json

Hilco Wijbenga· Feb 9, 2012, 21:10 UTC · lore

Hi all,

This is a bit silly but I'm trying to time how long it takes to enter a Git controlled directory. I guess this is more of a GNU/Linux question then anything else.

I've noticed that entering a Git controlled project directory takes quite some time so I wanted to measure exactly how much (it's the prompt I'm using that's taking the time, I suspect). I first tried (a bit naive, I admit :-) )

time cd my-project

This doesn't work of course. Obviously, writing a script doesn't work either because then the prompt isn't calculated. Next I tried

date +%H:%M:%S.%N ; cd my-project-abc ; date +%H:%M:%S.%N

but, surprisingly (to me), that doesn't work either. It simply prints the two timestamps and *then* does the cd (or, at least, that's how it seems to behave).

So how would one do this? :-)

Cheers, Hilco

P.S. This slow cd is only the first time, afterwards things have been cached.

Seth Robertson· Feb 9, 2012, 21:16 UTC · re: Hilco Wijbenga · lore

Re: Silly Question About Timing

In message <CAE1pOi1+FQNoPZ_P-fmFx-YhnUYzMQT=6zh3s-OyT71vcDm=wQ@mail.gmail.com>, Hilco Wijbenga writes:

    I've noticed that entering a Git controlled project directory takes
    quite some time so I wanted to measure exactly how much (it's the
    prompt I'm using that's taking the time, I suspect). I first tried (a
    bit naive, I admit :-) )

    time cd my-project

Your confusion is because you are measuring the wrong thing. I'm assuming, here, that you have a shell prompt which is giving you all sorts of status about the git repository. The "cd" operation is instantaneous, it is the shell attempting to compute the new prompt which is slow.

Exactly how your shell does this is shell dependent, but you might want to look at your setting of $PROMPT_COMMAND. Then you can test it by running something like:

time sh -c "cd git-directory; $PROMPT_COMMAND"

					-Seth Robertson

Hilco Wijbenga· Feb 9, 2012, 21:48 UTC · re: Seth Robertson · lore

Re: Silly Question About Timing

On 9 February 2012 13:16, Seth Robertson <in-gitvger@baka.org> wrote:

Show 15 quoted lines

>
> In message <CAE1pOi1+FQNoPZ_P-fmFx-YhnUYzMQT=6zh3s-OyT71vcDm=wQ@mail.gmail.com>, Hilco Wijbenga writes:
>
>    I've noticed that entering a Git controlled project directory takes
>    quite some time so I wanted to measure exactly how much (it's the
>    prompt I'm using that's taking the time, I suspect). I first tried (a
>    bit naive, I admit :-) )
>
>    time cd my-project
>
> Your confusion is because you are measuring the wrong thing.  I'm
> assuming, here, that you have a shell prompt which is giving you all
> sorts of status about the git repository.  The "cd" operation is
> instantaneous, it is the shell attempting to compute the new prompt
> which is slow.

Yes, exactly.

Show 5 quoted lines

> Exactly how your shell does this is shell dependent, but you might
> want to look at your setting of $PROMPT_COMMAND.  Then you can test it
> by running something like:
>
> time sh -c "cd git-directory; $PROMPT_COMMAND"

I tried that and it's still instantaneous.

The culprit is

export PS1='\[\033[01;32m\]\u@\h\[\033[01;34m\] \w \W$(__git_ps1 " (%s)")\$\[\033[00m\] '

but I can't get that to run. Simply running

echo $PS1

doesn't work and I have been unable to get the __git_ps1 part to do anything.

Frans Klaver· Feb 9, 2012, 21:54 UTC · re: Hilco Wijbenga · lore

Re: Silly Question About Timing

On Thu, 09 Feb 2012 22:48:25 +0100, Hilco Wijbenga <hilco.wijbenga@gmail.com> wrote:

> ... and I have been unable to get the __git_ps1 part to do anything.

I get the following on msysgit:

/c/msysgit (devel) $ time __git_ps1 (devel) real 0m0.406s user 0m0.136s sys 0m0.107s

Would be odd if that doesn't work on Linux.