[systemd-devel] [PATCH] use dolt.m4 to speedup compilation

[Randy Witt]

On 03/05/2015 05:33 PM, Lucas De Marchi wrote:
> On Thu, Mar 5, 2015 at 9:58 PM,  <josh at joshtriplett.org> wrote:
>> On Fri, Mar 06, 2015 at 12:55:38AM +0100, Michael Biebl wrote:
>>> 2015-03-05 11:58 GMT+01:00  <harald at redhat.com>:
>>>> From: Harald Hoyer <harald at redhat.com>
>>>>
>>>> The speedup is significant
>>>>
>>>> Original libtool
>>>> $ ccache -C && make clean && time make -j4
>>>> […]
>>>> real    6m4.104s
>>>> user    13m49.234s
>>>> sys    7m37.864s
>>>>
>>>> Original libtool + dolt
>>>> $ ccache -C && make clean && time make -j4
>>>> […]
>>>> real    2m24.869s
>>>> user    7m30.198s
>>>> sys    1m17.813s
>>>
>>> Hm, the speedup is nowhere near as significant here:
>>> without dolt (make):
>>> real 4m2.749s
>>> user 3m9.304s
>>> sys 0m19.032s
>>>
>>> with dolt (make):
>>> real 3m33.756s
>>> user 2m59.476s
>>> sys 0m17.632s
>>>
>>> without dolt (make -j6):
>>> real 1m42.001s
>>> user 5m3.680s
>>> sys 0m26.608s
>>>
>>> with dolt (make -j6)
>>> real 1m35.267s
>>> user 4m50.956s
>>> sys 0m24.724s
>>>
>>>
>>> libtool version is 2.4.2.
>>
>> That's more what I'd expect with current versions of libtool, which has
>> supposedly fixed many of the issues that motivated the creation of dolt
>> in the first place.
>
> Maybe it was a regression in libtool from 2.4.2 <-> 2.4.5?  I have 2.4.5 here:

We saw noticeable slowdowns in Yocto after upgrading as well.

http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=1f53edeaf9ea59dd55459a6d5a93829fb4983839

There were a number of patches submitted and evidently 2.6 is back to previous 
speeds.

> make -j6, libtool
> real    4m53.924s
> user    11m4.323s
> sys     0m54.880s
>
> make -j6, dolt
> real    1m58.653s
> user    6m20.523s
> sys     0m28.920s
>
>