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cpu flags questions


What should i add to my make.conf?

When typing cat /proc/cpuinfo i get this:





processor    : 0
vendor_id    : AuthenticAMD
cpu family    : 21
model        : 2
model name    : AMD FX-8320 Eight-Core Processor
stepping    : 0
microcode    : 0x6000822
cpu MHz        : 1700.000
cache size    : 2048 KB
physical id    : 0
siblings    : 8
core id        : 0
cpu cores    : 4
apicid        : 16
initial apicid    : 0
fpu        : yes
fpu_exception    : yes
cpuid level    : 13
wp        : yes
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb arat cpb hw_pstate npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold vmmcall bmi1
bugs        : fxsave_leak
bogomips    : 7585.92
TLB size    : 1536 4K pages
clflush size    : 64
cache_alignment    : 64
address sizes    : 48 bits physical, 48 bits virtual
power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro

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Excuse me Cardinal .... I hope not to bored You for my "intromission" ......


There is the possibility of use "-march=native" instead -march=core_abcxyz ....


with this little script you can see if there are differences launching once with native and in another terminal wi -march=your_subarch 

echo 'int main(){return 0;}' > test.c && gcc -v -Q -march=native -O2 test.c -o test && rm test.c test

for example i've an haswell 4771; there are 2 or 3 new instructions respect for example an Haswell 4730 K



The 2nd thing:


I use for LDFLAGS 

LDFLAGS="${LDFLAGS} -Wl,--hash-style=gnu"



The last: if you use Gentoo-sources and you want to compile using specific instructions, you must at first abilitate the "experimental" USE; then:

# euse -E experimental -p sys-kernel/gentoo-sources && emerge gentoo-sources

(this will be "visible" in /etc/portage/package.use)


If You use "Stable with kernel 4.0.5 you'll be able to use also the BFQ scheduler





I whish that i have not bored You .......  (excuse me Cardinal)


good work !!!!!!!!! 



PS: Ah remember to use:

# emerge cpuinfo2cpuflags

and add the output to the make.conf.

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cpuinfo2cpuflags-x86 give me this:


CPU_FLAGS_X86: aes avx fma3 fma4 mmx mmxext popcnt sse sse2 sse3 sse4_1 sse4_2 sse4a ssse3 xop
so i added that to /etc/portage/make.conf

like this:

CPU_FLAGS_X86="aes avx fma3 fma4 mmx mmxext popcnt sse sse2 sse3 sse4_1 sse4_2 sse4a ssse3 xop"
Thanks a lot

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