Dne 2.10.2014 v 10:40 Ralf Corsepius napsal(a):
On 10/02/2014 09:47 AM, Zdenek Kabelac wrote:
Dne 2.10.2014 v 08:33 Lennart Poettering napsal(a):
On the other hand - usage of dash significantly speeds up compilation of
autoconf projects - it's pretty interesting to see the compilation with
dash
is then maybe even 50% faster in non optimized builds (depends on how
many shells are forked during autoconf builds)
I don't know what you tested, but I don't see a substantial speed up on
running autoconf-generated configure scripts:
# time SHELL=/bin/bash CONFIG_SHELL=/bin/bash /bin/bash ../configure ...
...
real 0m5.775s
user 0m0.528s
sys 0m0.217s
# time SHELL=/bin/dash CONFIG_SHELL=/bin/dash /bin/dash ../configure ...
...
real 0m5.495s
user 0m0.340s
sys 0m0.194s
Another, more extensive test case:
* bash;
real 1m43.115s
user 0m34.708s
sys 0m16.322s
* dash:
real 1m33.283s
user 0m30.834s
sys 0m13.932s
In other words, I am observing a 5-10% speed up on running autoconf configure
scripts.
Unsure how does your 'bash' environment setup looks like - but on pretty
simple lvm configure case - but my rawhide (on C2D 2.1GHz, SSD)
dash:
real 0m2.819s
user 0m0.770s
sys 0m2.098s
bash:
real 0m3.600s
user 0m1.211s
sys 0m2.695s
xf86-video-intel (intel drm driver)
dash:
real 0m8.691s
user 0m4.639s
sys 0m4.153s
bash:
real 0m9.852s
user 0m5.241s
sys 0m4.982s
It used to give significant boost for automake & libtool based software -
however at some point libtool started to use bashisms and so you cannot just
replace /bin/sh -> dash - as build will fail.
(zsh doesn't seem to boost the speed)
Also I said - upto 50% - which depends on complexity of configure files.
But even your personally measured 10% speed is in my eyes pretty significant
if you do builds all day and surely outweighs some RAM (and IMHO even RAM will
be actually still positive anyway on dash side if you do parallel builds)
Zdenek
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