[OE-core] Fetch/Unpack performance dependent on git version

[Michael Halstead]

On 04/19/2014 03:40 PM, Richard Purdie wrote:
> I thought it might be worth highlighting to people that the performance
> of the git fetcher *and* the unpack process is highly dependant on the
> version of git.
>
> Firstly, all versions of git 1.6+ appear to default to injecting an
> fsync() after fetching objects. fsync() usage significantly hurts our
> builds. It is also a bit pointless in our usecase, we can however
> disable it with a simple tweak to the fetcher:
>
> -        ud.basecmd = data.getVar("FETCHCMD_git", d, True) or "git"
> +        ud.basecmd = data.getVar("FETCHCMD_git", d, True) or "git -c core.fsyncobjectfiles=0"
>
> Secondly, for older versions of git, git clone is running repository
> coverage checks even for local cloning. E.g.:
>
> git version 1.8.3.2 on my system:
>
> $ bitbake linux-yocto -c fetch
> $ time bitbake linux-yocto -c unpack
> 51.33user 1.93system 1:09.27elapsed 76%CPU (0avgtext+0avgdata 779380maxresident)k
>
> after updating to git 1.9.2:
>
> $ bitbake linux-yocto -c fetch
> $ time bitbake linux-yocto -c unpack
> 4.28user 0.63system 0:04.36elapsed 112%CPU (0avgtext+0avgdata 260692maxresident)k
>
> so 16 times faster!
>
> The commit in question for anyone interested:
>
> https://github.com/git/git/commit/125a05fd0b45416558923b753f6418c24208d443
>
> Michael/Beth: Can we please upgrade the autobuilder to a daisy release
> buildtools tarball which has git 1.9.x in it? This should massively
> speed up certain parts of the autobuilder.
The new buildtools are installed at /opt/poky/1.6 and I've updated
~pokybuild/.bashrc to source them. Restarting all the buildslaves should
put them to use. I'll restart all of them that aren't building
currently. opensuse131-a.yp, on the current nightly, is the only one
occupied at the moment.

Michael Halstead
Yocto Project / System Administrator


>
> Stefan: Could you see which version of git is on the performance
> benchmark machine? A run with the daisy build tools tarball would be
> extremely interesting if its before 1.9.
>
> Cheers,
>
> Richard
>
>
>


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