[OE-core] [PATCH] kernel: Use hardlinks for do_populate_sysroot for speed

[Richard Purdie]

On Sat, 2013-11-09 at 21:38 +0100, Andrea Adami wrote:
> On Fri, Nov 8, 2013 at 6:23 PM, Hart, Darren <darren.hart at intel.com> wrote:
> > On Fri, 2013-11-08 at 16:50 +0000, Richard Purdie wrote:
> >> On Fri, 2013-11-08 at 10:59 -0500, Bruce Ashfield wrote:
> >> > On 13-11-08 10:55 AM, Richard Purdie wrote:
> >> > > On Fri, 2013-11-08 at 10:41 -0500, Bruce Ashfield wrote:
> >> > >> On 13-11-08 10:18 AM, Richard Purdie wrote:
> >> > >>> The kernel tree is large and doesn't need to be copied. Override
> >> > >>> the default sysroot handling function to use a hardlink copying
> >> > >>> function in python.
> >> > >>>
> >> > >>> This commit also drops the copying of the /lib directory which
> >> > >>> just contains the kernel modules. We never use those in the sysroot
> >> > >>> so there is little point in carrying those around.
> >> > >>>
> >> > >>> For linux-yocto this takes the do_populate_sysroot time 24s -> 14s.
> >> > >>
> >> > >> Fantastic. One less thing for me to dig into later. I thought this
> >> > >> was already in place, so I'm pleasantly surprised that there was a
> >> > >> time savings to be found!
> >> > >
> >> > > I was somewhat surprised too.
> >> > >
> >> > > We still need to optimise what we install in do_install since that is
> >> > > where significant gains can still be made.
> >> >
> >> > Agreed. I started some changes in that area right after ELC-e, I'll
> >> > try and get them out sooner rather than later.
> >>
> >> I thought I'd share this for people's interest:
> >>
> >> http://dan.rpsys.net/kernelbuildissue.png
> >>
> >> Its the output from pybootchart of a bitbake core-image-sato from
> >> scratch. I've zoomed out to put some bars in particular into
> >> perspective.
> >>
> >> The pink colour is linux-yocto:do_install, the cyan is
> >> linux-yocto:do_package and the blue is linux-yocto:do_populate_sysroot.
> >> The uncoloured bar at the bottom is linux-yocto:do_package_write_rpm.
> >>
> >> So the final thing to build is the kernel by quite some margin, its
> >> holding the rest of the build up.
> >>
> >> Hopefully these patches start to improve that a bit!
> >>
> >
> > Yup, linux-yocto do_package is the biggest build-time hindrance for me
> > and something we've wanted to look into for a long time. Great to see
> > some progress.
> >
> > --
> > Darren Hart
> > Intel Open Source Technology Center
> > Yocto Project - Linux Kernel
> >
> > _______________________________________________
> > Openembedded-core mailing list
> > Openembedded-core at lists.openembedded.org
> > http://lists.openembedded.org/mailman/listinfo/openembedded-core
> 
> On my old quad core:
> 
> Before: 95.24 seconds
> After: 83.25 seconds

We have some "standard" tests we use for comparison purposes as detailed
on:

https://wiki.yoctoproject.org/wiki/Performance_Test

Some numbers from master and a test branch containing the recent
speedups:

fedora19,master:d6cc7c8ed76c8b1117cf03c7bd4b0742f98f79b3,poky-10.0.0.final-359-gd6cc7c8,1:22:37,12:05.50,1:17:53,4:02.68,0:31.71,0:15.70,0:01.61,26347744,5035816
fedora19,master:d6cc7c8ed76c8b1117cf03c7bd4b0742f98f79b3,poky-10.0.0.final-359-gd6cc7c8,1:22:59,12:09.26,1:17:29,4:06.75,0:31.82,0:15.69,0:01.70,26348556,5035876
fedora19,master:d6cc7c8ed76c8b1117cf03c7bd4b0742f98f79b3,poky-10.0.0.final-359-gd6cc7c8,1:22:21,12:07.23,1:18:21,4:07.44,0:31.79,0:15.63,0:01.62,26351088,5035908
fedora19,master:d6cc7c8ed76c8b1117cf03c7bd4b0742f98f79b3,poky-10.0.0.final-359-gd6cc7c8,1:23:16,12:15.33,1:18:00,4:02.50,0:31.87,0:15.74,0:01.63,26348132,5035848
fedora19,rpurdie/timing:9d8c0ef3349936b3bd0bbf485b50cf81f4feaf80,poky-10.0.0.final-373-g9d8c0ef,1:19:42,10:28.53,1:15:30,4:12.24,0:31.30,0:15.69,0:01.66,26137344,5055628
fedora19,rpurdie/timing2:eb2221d6247c12322ac38b9ac6f24c9de5877e53,poky-10.0.0.final-401-geb2221d,1:18:51,10:44.26,1:16:32,4:13.47,0:31.27,0:15.69,0:01.65,26137828,5055916

So we have 1:23m -> 1:19m for overall buildtime and 12.0m -> 10.5m for
"bitbake virtual/kernel" from cleansstate. Not too bad :)

Thanks to Stefan for running the tests!

Cheers,

Richard