Re: "Cannot fetch git.git" (worktrees at fault? or origin/HEAD) ?

From: Stefan Beller <sbeller@google.com>
Date: Nov 3, 2017, 19:11 UTC
Message-ID: <CAGZ79kY+R_Kd7BbmnRb0C1H94HvZ3TGRvWKFOX8XEStjBQMB-A@mail.gmail.com>
In-Reply-To: <0f1f8317-9d82-5e61-5332-f877ca886056@gmail.com>

On Fri, Nov 3, 2017 at 2:32 AM, Kaartic Sivaraam <kaartic.sivaraam@gmail.com> wrote:

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> On Monday 23 October 2017 11:07 PM, Stefan Beller wrote:
>>
>> Exactly. By memory I mean volatile RAM (as opposed to
>> memory on a spinning disk).
>>
>> Using GIT_TEST_OPTS has had some issues (I remember vaguely
>> there was an inconsistency between the output of `make test` and prove),
>> so I put my entire working tree on a tmpfs, I run roughly this script
>> after booting my computer:
>>
>>    sudo mount -t tmpfs -o size=16g tmpfs /u
>>    mkdir /u/git
>>    echo "gitdir:
>> /usr/local/google/home/sbeller/OSS/git/.git/worktrees/git"
>>>
>>> /u/git/.git
>>
>>    git -C /u/git checkout -f HEAD
>>
>>    cat <<EOF >/u/config.mak
>>    DEVELOPER=1
>>    DEVELOPERS=1
>>    CFLAGS += -g -O2
>>    CFLAGS += -DFLEX_ARRAY=2048
>>    #CFLAGS += -Wno-unused-value
>>    EOF
>
>
> Did I thank you for a good explanation? If not, thanks that was interesting
> and enlightening.
>
>> The test suite (excluding t9*) runs in less than 50 seconds on the ram
>> disk.
>>

Just tested again, I meant to say 70s instead of 50s.

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> BTW, this is what I call _way way_ faster. Unfortunately due to the limited
> configuration of my system, the test suite has following timing
>
>     real    3m14.482s
>     user    2m10.556s
>     sys     1m12.328s

This sounds to me as if it is running with just one thread (because sys+user = real); I usually run with

    cd t
    prove --jobs 25 t[0-8][0-9]*.sh

The multithreading can be seen in the timing as well
    real 1m9.913s
    user 1m50.796s
    sys 0m54.092s
as user > real already.

If you run tests via 'make test' or 'cd t && make', you can also give a --jobs <n> to make it faster. I have no good answer for how many, but I have the impression overloading the system is no big deal. (I only have a few cores in this machine, 4 or 6, but still run with --jobs 25; 'git grep sleep' returns a couple of lines, and such threads sleeping definitely don't need a CPU)

Thanks, Stefan