[PATCH] [DOCS] How to Add a Builder

[Mikael Lyngvig]

Perhaps I've misunderstood something.  I thought the builders restarted
from scratch each and every time so as to ensure that the complete product
builds reliably.  This to ensure that the project doesn't gradually rot.

If the builders simply update and remake, then there's absolutely no point
in using ccache, I agree wholeheartedly to that.

Is anybody with knowledge of the buildbot system listening in?  Do the
builders start from scratch each time or do they simply resume and continue
after having performed an "svn update"?  The build times strongly suggest
that they start over from scratch, at least some of them.


-- Mikael




2013/11/14 Reid Kleckner <rnk at google.com>

> Starting from scratch seems undesirable.  ccache is basically just undoing
> that for you.
>
>
> On Wed, Nov 13, 2013 at 9:46 PM, Mikael Lyngvig <mikael at lyngvig.org>wrote:
>
>> The problem is specific to the buildbot slaves that always start from
>> scratch.  Otherwise, I agree with your views.
>>
>>
>> -- Mikael
>>
>>
>> 2013/11/14 Reid Kleckner <rnk at google.com>
>>
>>> IMO ccache is unnecessary if you use cmake+ninja.  They actually track
>>> header dependencies well, so as long as you don't clean your build
>>> directory, you'll have fast, correct incremental builds.  ccache won't save
>>> much in that situation because the preprocessed source will actually be
>>> different.
>>>
>>>
>>> On Wed, Nov 13, 2013 at 9:12 PM, Mikael Lyngvig <mikael at lyngvig.org>wrote:
>>>
>>>> Hi,
>>>>
>>>> The patch basically tells that ccache is very usable for low-end Linux
>>>> systems and briefly how to get going using ccache (one special option is
>>>> needed, thanks to Dimitri Gribenko, for sharing this).
>>>>
>>>> On my ARMv7 a repeat clean build takes less than 1/3rd the time of the
>>>> initial clean build.  So it is definitely something that the slow builders
>>>> can benefit from.  A build time of 36 minutes was reduced to approximately
>>>> 11.5 minutes.
>>>>
>>>> I suspect it might better be put in the GettingStarted document, but I
>>>> need feedback on this.
>>>>
>>>> If anybody dislikes the idea of putting this patch in the LLVM
>>>> documentation, then please think of the fact that LLVM benefits greatly
>>>> from the builders doing their job as fast as at all possible.
>>>>
>>>>
>>>> -- Mikael
>>>>
>>>>
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>>>>
>>>>
>>>
>>
>
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