On 2016-09-07 8:33 AM, Markus Lehtonen wrote:
On Wed, 2016-09-07 at 07:56 -0400, Bruce Ashfield wrote:On 2016-09-07 5:27 AM, Richard Purdie wrote:Hi Bruce,I deliberately spaced out the merges of various things so we could get performance measurements of the system as it happened. Unfortunately the 4.8 kernel appears to regress the kernel build time quite significantly: The raw data: ypperf02,master:9428b19a7dd1d265d9f3211004391abe33ea0224,uninative-1.3 -414 -g9428b19,1:01:32,4:21.16,1:00:32,2:10.86,0:16.19,0:11.21,0:01.20,5:34. 73,26701616,6445160,1477762,5446116 ypperf02,master:9428b19a7dd1d265d9f3211004391abe33ea0224,uninative-1.3 -414 -g9428b19,1:04:14,4:23.82,1:00:40,2:13.70,0:16.18,0:11.28,0:01.22,5:45. 48,26697516,6445724,1478048,5446490 ypperf02,master:b9d90ace005597ba35b59adcd8106a1c52e40c1a,uninative-1.3 -438 -gb9d90ac,1:03:16,7:22.13,1:02:46,2:16.60,0:16.32,0:11.04,0:01.21,5:42. 11,30852876,10550952,1707255,5912282 ypperf02,master:f7ca989ddc6d470429b547647d3fbaad83a982d9,uninative-1.3 -446 -gf7ca989,1:04:42,7:29.05,1:03:04,2:19.71,0:16.21,0:11.05,0:01.24,5:52. 83,30845748,10551316,1707615,5912122 which shows the time for "bitbake virtual/kernel -c cleansstate; time bitbake virtual/kernel" goes from 4:20 to 7:22. The disk footprint of the build went from 26GB to 30GB. The build with rm_work size went from 6.4GB to 10.5GB. The overall build time went up 2-3 minutes which looks like the increased kernel build time. The increased time may well be from the increased data being generated/processed.Is it the actual compile itself ? What's the trick to actually get individual task For the disk footprint, I can check the refs in the tree and purge anything that may be dangling. That being said, I can't do that to the repository on the git server, so we may need someone that can issue a git gc directly on the repository.We can't ship M3 with this much of a performance degradation and increased space usage :(. Any idea what changed?Nope. I can only focus on one thing at a time. I was worried about a functionally correct kernel (which I still am) and haven't looked at anything in the peripheral yet. If I can get individual task timings, I can look at it more. I'm seeing significantly faster meta data phases, etc, so I'm interested to know if this is purely in the build steps.In my own test setup I'm seeing similar increase in kernel build time. Comparing the buildstats of kernel builds from before and after the 4.8 I got the following numbers (these are cpu times consumed by the tasks TASK ABSDIFF RELDIFF CPUTIME1 CPUTIME2 do_package +17.5s +133.1% 13.1s -> 30.6s do_deploy +19.9s +1449.4% 1.4s -> 21.3s do_package_write_rpm +86.8s +714.7% 12.1s -> 98.9s do_compile_kernelmodules +139.4s +35.9% 388.2s -> 527.6s do_compile +201.1s +30.0% 670.3s -> 871.4s
ok. So as long as the significant increases aren't in do_kernel_metadata or do_patch (those two I've measured), we are dealing with something in the kernel build itself. I can deal with the footprint by inspecting the repo, but Kbuild is a tougher nut to crack. Out of curiosity, is the 4.4 kernel on master showing a significantly shorter build time ? I'm assuming the before is the 4.4 kernel .. but I just wanted to be sure, so we can rule out something else that might be pathologically reacting to the sheer amount of I/O in a kernel build. Bruce
I haven't tried to analyze what is causing this yet, though. Thanks, Markus
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