Bug 12603

Summary:	Performance regression with new kernel upgrade
Product:	[Build System, Metadata & Runtime] OE-Core	Reporter:	Ross Burton <ross.burton>
Component:	kernel	Assignee:	Bruce Ashfield <bruce.ashfield>
Status:	RESOLVED FIXED	QA Contact:
Severity:	normal
Priority:	Undecided	CC:	tom.zanussi
Version:	2.5
Target Milestone:	---
Hardware:	x86
OS:	Multiple
Whiteboard:
OS type for building Yocto:	---	Type of Regression:	---
Verified:		Documentation change:	No (bug/feature does not impact docs)

Description Ross Burton 2018-03-14 03:48:46 UTC

Since the last kernel upgrade in oe-core 62acf087dca83ff094b1c0300b5752978807ca17 the speed of building the kernel changed massively.

buildstats-diff output of the that commit and before the kernel bumps:

  PKG            TASK                      ABSDIFF   RELDIFF  CPUTIME1 -> CPUTIME2
  linux-yocto    do_package                  22.3s   +194.7%     11.5s -> 33.8s
  linux-yocto    do_deploy                   30.1s  +1557.3%      1.9s -> 32.0s
  linux-yocto    do_package_write_ipk       135.0s   +348.8%     38.7s -> 173.7s
  linux-yocto    do_compile_kernelmodules   142.0s    +17.8%    799.7s -> 941.8s
  linux-yocto    do_package_write_rpm       158.9s   +574.1%     27.7s -> 186.6s
  linux-yocto    do_compile                 174.7s    +18.7%    933.3s -> 1108.0s

Longer to compile, a lot longer to deploy and package.

Comment 1 Ross Burton 2018-03-14 05:42:49 UTC

The problem is the 'linux-yocto: aufs and systemtap' commit which enables CONFIG_KERNEL_DEBUG.

packages/qemux86-poky-linux/linux-yocto/kernel-vmlinux: PKGSIZE changed from 19587044 to 300944172 (+1436%)

Yes, that's 19M to 300M.

Comment 2 Bruce Ashfield 2018-03-14 05:54:33 UTC

I'll revert the patch that enabled debug, and send it along shortly.

Comment 3 Ross Burton 2018-03-15 07:54:27 UTC

Fixed in oe-core ad8f68e9831c57fde62f7b1942bfa9e1307f113d