Better Multicore support

LeSnake · April 22, 2020, 11:45am

I saw, that , espessialy while installing, only one core is used. the taskmanager plugin looks often like that:

While researching i saw, that his could be there because the new kernel.
Do someone know if this true and is there an prgram to fix this?

joekamprad · April 22, 2020, 2:51pm

MAKEFLAGS="-j$(nproc)"
inside makepkg.conf can enable multicore support for bulding packages… (AUR)

https://wiki.archlinux.org/index.php/Makepkg#Improving_compile_times

famewolf · April 23, 2020, 3:37am

By default it seems to be hardcoded to use 2 cores even on my single core system.

It’s worth switching to -march=native and losing the generic mtune too if you want “peak performance”.

LeSnake · April 23, 2020, 7:37am

what is -march=native exactly and how to setup this tweak?

joekamprad · April 23, 2020, 9:23am

that’s rare today

joekamprad · April 23, 2020, 9:24am

#########################################################################
# ARCHITECTURE, COMPILE FLAGS
#########################################################################
#
CARCH="x86_64"
CHOST="x86_64-pc-linux-gnu"

#-- Compiler and Linker Flags
CPPFLAGS="-D_FORTIFY_SOURCE=2"
CFLAGS="-march=x86-64 -mtune=generic -O2 -pipe -fno-plt"
CXXFLAGS="-march=x86-64 -mtune=generic -O2 -pipe -fno-plt"
LDFLAGS="-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now"
#-- Make Flags: change this for DistCC/SMP systems
#MAKEFLAGS="-j2"
MAKEFLAGS="-j$(nproc)"
#-- Debugging flags
DEBUG_CFLAGS="-g -fvar-tracking-assignments"
DEBUG_CXXFLAGS="-g -fvar-tracking-assignments"

LeSnake · April 23, 2020, 9:44am

helped, dont needed to add -march=native

Is there also an way to enable multicore for pacman?

Halcek · April 23, 2020, 9:44am

Just edit the ARCHITECTURE section in sudo nano /etc/makepkg.conf file.

LeSnake · April 23, 2020, 9:45am

do you also know a way to enable multicore for pacman?

LeSnake · April 23, 2020, 9:55am

https://bbs.archlinux.org/viewtopic.php?id=168156

found this by reaerch but i think this shouldnt be the problem because my xz is on version 5.2.5 and in the post they speak from xz 5.0.5

famewolf · April 23, 2020, 3:47pm

True…I’ve got a dual core on order for it but it’s coming from china…

famewolf · April 23, 2020, 3:49pm

Since GCC 4,2 or so it’s been able to determine what works best for the particular system it’s running on rather than you guessing. Specifying native tells it to do so. Works especially well with kernel compiles (choice 42 in the PKGBUILD).

CFLAGS="-march=native -O2 -pipe -fno-plt"
CXXFLAGS="-march=native -O2 -pipe -fno-plt"