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antonellocaroli
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Joined: 11 Aug 2016
Posts: 196

PostPosted: Sun Jul 08, 2018 6:55 am    Post subject: Chiarimento cpu_flags_x86 Reply with quote

Mi chiedevo se per alcuni programmi tipo ffmpeg
conviene avere attive tutte le cpu_flags_x86 disponibili per la propia cpu...o sceglierne solo alcune...cambiano le performance?
tipo nel mio caso

Code:
- - cpu_flags_x86_3dnow    : Use the 3DNow! instruction set
 - - cpu_flags_x86_3dnowext : Use the Enhanced 3DNow! instruction set
 - - cpu_flags_x86_aes      : Enable support for Intel's AES instruction set (AES-NI)
 - - cpu_flags_x86_avx      : Adds support for Advanced Vector Extensions instructions
 - - cpu_flags_x86_avx2     : Adds support for Advanced Vector Extensions 2 instructions
 - - cpu_flags_x86_fma3     : Use the Fused Multiply Add 3 instruction set ([fma] in cpuinfo)
 - - cpu_flags_x86_fma4     : Use the Fused Multiply Add 4 instruction set
 + + cpu_flags_x86_mmx      : Use the MMX instruction set
 + + cpu_flags_x86_mmxext   : Use the Extended MMX instruction set (a subset of SSE) ([mmxext] or [sse] in cpuinfo)
 + + cpu_flags_x86_sse      : Use the SSE instruction set
 + + cpu_flags_x86_sse2     : Use the SSE2 instruction set
 + - cpu_flags_x86_sse3     : Use the SSE3 instruction set ([pni] in cpuinfo, NOT ssse3)
 + - cpu_flags_x86_sse4_1   : Enable SSE4.1 instruction support
 + - cpu_flags_x86_sse4_2   : Enable SSE4.2 instruction support
 + - cpu_flags_x86_ssse3    : Use the SSSE3 instruction set (NOT sse3/pni)
 - - cpu_flags_x86_xop      : Enable the XOP instruction set
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sabayonino
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Joined: 03 Jan 2012
Posts: 594

PostPosted: Sun Jul 08, 2018 7:53 am    Post subject: Reply with quote

se esegui

Code:
cpuid2cpuflags
CPU_FLAGS_X86: aes avx avx2 f16c fma3 mmx mmxext pclmul popcnt sse sse2 sse3 sse4_1 sse4_2 ssse3


Quello che otterrai sono le flags supportate dal tuo processore (ovviamente cambieranno da processore a processore)

Se abilitate sicuramente l'applicazione che ne avrà il supporto ne gioverà in termini di performance in quanto sfrutterà tutto il potenziale disponibile.

nel make.conf andrai ad inserire la seguente USE flag (definita espansa) con l'elenco delle flags indicate dal comando

Esempio
Code:
[...]
CPU_FLAGS_X86="aes avx avx2 f16c fma3 mmx mmxext pclmul popcnt sse sse2 sse3 sse4_1 sse4_2 ssse3"
[...]


ed eventualmente un bel
Code:
# emerge -DNa @world

per abilitare il supporto delle flags ai pacchetti che ancora non l'hanno ricevuto
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fedeliallalinea
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Joined: 08 Mar 2003
Posts: 19441
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PostPosted: Sun Jul 08, 2018 3:21 pm    Post subject: Reply with quote

sabayonino wrote:
se esegui

Code:
cpuid2cpuflags
CPU_FLAGS_X86: aes avx avx2 f16c fma3 mmx mmxext pclmul popcnt sse sse2 sse3 sse4_1 sse4_2 ssse3

Ovviamente devi installare il pacchetto app-portage/cpuid2cpuflags. Comunque come datto da sabayonino usa questo programma e abilita quello che ti propone
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oscarandrea
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Joined: 27 Nov 2015
Posts: 161
Location: Italy/Cosenza

PostPosted: Tue Jul 10, 2018 8:13 am    Post subject: Re: Chiarimento cpu_flags_x86 Reply with quote

antonellocaroli wrote:
Mi chiedevo se per alcuni programmi tipo ffmpeg
conviene avere attive tutte le cpu_flags_x86 disponibili per la propia cpu...o sceglierne solo alcune...cambiano le performance?
tipo nel mio caso

Code:
- - cpu_flags_x86_3dnow    : Use the 3DNow! instruction set
 - - cpu_flags_x86_3dnowext : Use the Enhanced 3DNow! instruction set
 - - cpu_flags_x86_aes      : Enable support for Intel's AES instruction set (AES-NI)
 - - cpu_flags_x86_avx      : Adds support for Advanced Vector Extensions instructions
 - - cpu_flags_x86_avx2     : Adds support for Advanced Vector Extensions 2 instructions
 - - cpu_flags_x86_fma3     : Use the Fused Multiply Add 3 instruction set ([fma] in cpuinfo)
 - - cpu_flags_x86_fma4     : Use the Fused Multiply Add 4 instruction set
 + + cpu_flags_x86_mmx      : Use the MMX instruction set
 + + cpu_flags_x86_mmxext   : Use the Extended MMX instruction set (a subset of SSE) ([mmxext] or [sse] in cpuinfo)
 + + cpu_flags_x86_sse      : Use the SSE instruction set
 + + cpu_flags_x86_sse2     : Use the SSE2 instruction set
 + - cpu_flags_x86_sse3     : Use the SSE3 instruction set ([pni] in cpuinfo, NOT ssse3)
 + - cpu_flags_x86_sse4_1   : Enable SSE4.1 instruction support
 + - cpu_flags_x86_sse4_2   : Enable SSE4.2 instruction support
 + - cpu_flags_x86_ssse3    : Use the SSSE3 instruction set (NOT sse3/pni)
 - - cpu_flags_x86_xop      : Enable the XOP instruction set

certamente conviene aver abilitate tutte quelle disponibili dal processore, non fanno altro che sfruttare delle istruzione specifiche del processore per migliorare quello che sono le perfomance del software in esecuzione
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