[CMake] FYI - From Ninja-build mailing list - Fwd: Proposal: restat rules

[Peter Kümmel]

On 30.09.2011 19:16, Eric Noulard wrote:
> 2011/9/30 Alexander Neundorf<a.neundorf-work at gmx.net>:
>>> Summary:
>>>
>>>           build    dry    rebuild
>>> ninja   1m15.8   0m0.1    0m07.3
>>> make    1m19.4   0m1.4    0m07.9
>>> auto    3m19.9   0m2.1    0m13.0
>>>
>>> So only the dry run shows a huge speedup (10-20 times faster)
>>
>> Not to question your numbers, but shouldn't the difference of the dryrun
>> (1.3s) also be present in the rebuild ?

'rebuild' is the time after a 'touch':

    touch ../trunk/src/LyX.cpp
    time ninja

means compiling one file plus the time for linking.
Yes, makes not much sense to measure this time here because
compiling and linking is independent of the ninja/make.


>> I mean, this should be the time ninja is faster in checking whether any file
>> changed, and in the rebuild case it has to do that too, and additionally build
>> one file ?
>>
>> How often did you measure this, just once or multiple times ?
>

Cache was warm and the time was a typical one of multiple runs.

> I was about to comment about this too.
> If you do test ninja first on a pristine source tree and then
> make then make will certainly take advantage of the VFS caching almost
> all source file access.
>
> May be it would necessary to untar the source (in different temp dir )
> before each test sets.
> but may you already did this.
>

I did the opposite, measured with a 'warm' cache.

Peter

> Or may be I should just try myself :-]
>
>