[OE-core] linux-yocto task performance numbers

[Richard Purdie]

As people know, I've been looking at performance a little, one of the
benchmarks is how long the kernel takes to build. I dumped out the task
performance data from buildstats for a linux-yocto build (nothing else
running): 

do_fetch:                 Elapsed time: 0.04 seconds 
do_unpack:                Elapsed time: 1.61 seconds 
do_kernel_checkout:       Elapsed time: 4.39 seconds 
do_validate_branches:     Elapsed time: 0.47 seconds 
do_patch:                 Elapsed time: 57.77 seconds 
do_kernel_configme:       Elapsed time: 44.92 seconds 
do_kernel_configcheck:    Elapsed time: 8.94 seconds 
do_configure:             Elapsed time: 0.60 seconds 
do_compile:               Elapsed time: 72.95 seconds 
do_compile_kernelmodules: Elapsed time: 34.84 seconds 
do_populate_lic:          Elapsed time: 0.14 seconds 
do_strip:                 Elapsed time: 0.03 seconds 
do_uboot_mkimage:         Elapsed time: 0.03 seconds 
do_install:               Elapsed time: 1.87 seconds 
do_populate_sysroot:      Elapsed time: 0.16 seconds 
do_shared_workdir:        Elapsed time: 0.05 seconds 
do_sizecheck:             Elapsed time: 0.03 seconds 
do_bundle_initramfs:      Elapsed time: 0.03 seconds 
do_kernel_link_vmlinux:   Elapsed time: 0.03 seconds 
do_deploy:                Elapsed time: 13.17 seconds 
do_package:               Elapsed time: 31.54 seconds 
do_packagedata:           Elapsed time: 0.59 seconds 
do_package_qa:            Elapsed time: 5.30 seconds 
do_package_write_ipk:     Elapsed time: 83.24 seconds 
do_package_write_rpm:     Elapsed time: 44.58 seconds 

The "core" was getting blamed for a lot of the build time. As can be
seen, the "core" isn't taking that much time now, apart from the fact
that ipk packaging seems to be taking twice the time of rpm which needs
looking into.

Some tasks like the compile tasks are understandable and likely
minimised by upstream work already.

The other tasks which as consuming a disproportionate amount of time are
kernel_configme and patch, I believe we need to look into those a little
further too. To put it into context, should the kernel compile be at the
same order of magnitude as the patch and configure?

Cheers,

Richard