Re: [RFC] Performance Issue: Build time increases

[Robert Yang <liezhi.yang@windriver.com>]

On 08/15/2011 10:31 PM, Richard Purdie wrote:
> On Fri, 2011-08-12 at 19:06 +0800, Robert Yang wrote:
>> Hi folks,
>>
>> The build time of core-image-sato increases about 5 ~ 10 minutes than
>> the following commit:
>>
>> commit 5af197b55a4b779f1ec93186f0723026949ba2b5
>> Author: Liping Ke<liping.ke@intel.com>
>> Date:   Fri Jun 3 08:22:40 2011 +0800
>>
>>       cache: Implement multiple extra cache fields request support
>>
>> On my host,
>> 1) the build time of 5af197b55a4b779f1ec93186f0723026949ba2b5 is:
>>
>> real    208m26.133s
>> user    241m29.280s
>> sys     47m0.630s
>>
>> 2) and: 068839698fe192d8846c0ed4db65861448e8e524 is:
>>
>> real    217m39.687s
>> user    255m34.150s
>> sys     48m21.510s
>>
>>
>> I use the bisect build method to find out which patch causes the time
>> increases, but the build time is not stable on my host(Ubuntu 11.04 64bit),
>> e.g., the build time of 1) is 208m at the first build, then "git co
>> other_commit" and build it, after about 10 builds, then go back to build
>> 5af197b55a4b779f1ec, the build time will increases about 8 minutes, I have
>> stopped the X and cron, at. This may have relationship with the linux
>> distribution and disk.
>>
>> So I have to restart the build, reboot the machine by two days, and go on the
>> build. It would be better if anyone has other good method.
>>
>> I think that for the next release(e.g., yocto 1.2), we can find a clean and
>> stable machine(for the distribution, maybe RHEL is more stable than Ubuntu)
>> to check the build time weekly, so that we can notice the performance issue
>> early.
>
> I think we really need to get to the bottom of why the build times are
> so variable. Do we need to start doing these on a clean distro install?
> is a fresh boot good enough? is there a way we can clear out the VM

Hi Richard,

Thanks for you reply, yes, one build one restart(bitbake core-image-sato,
then restart the computer, and bitbake again) makes the build time stable.
I'm doing this now.

// Robert

> caches and get reproducible times? reformat the build partition?
>
> If that really is just because of the nature of a chaotic system, can we
> get some better representation of build time to use as a benchmark? We
> could really do with finding a faster test (which would hopefully still
> be representative)...
>
> Cheers,
>
> Richard
>
>
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