Am 09.04.2013 05:50, schrieb Nilesh Govindrajan: > I have two Gentoo VMs at Hetzner and the CPU supports 64 bit (grep lm > /proc/cpuinfo = true). > > But something funny, gcc -march=native -mtune=native -v -E - 2>&1 > </dev/null returns this: > > Using built-in specs. > COLLECT_GCC=/usr/x86_64-pc-linux-gnu/gcc-bin/4.6.3/gcc > COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.6.3/lto-wrapper > Target: x86_64-pc-linux-gnu > Configured with: > /var/tmp/portage/sys-devel/gcc-4.6.3/work/gcc-4.6.3/configure > --prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.6.3 > --includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/include > --datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.3 > --mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.3/man > --infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.3/info > --with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/include/g++-v4 > --host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --disable-altivec > --disable-fixed-point --without-ppl --without-cloog --enable-lto > --enable-nls --without-included-gettext --with-system-zlib > --enable-obsolete --disable-werror --enable-secureplt --enable-multilib > --enable-libmudflap --disable-libssp --enable-libgomp > --with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.6.3/python > --enable-checking=release --disable-libgcj --enable-libstdcxx-time > --enable-languages=c,c++,fortran --enable-shared --enable-threads=posix > --enable-__cxa_atexit --enable-clocale=gnu --enable-targets=all > --with-bugurl=http://bugs.gentoo.org/ --with-pkgversion='Gentoo 4.6.3 > p1.11, pie-0.5.2' > Thread model: posix > gcc version 4.6.3 (Gentoo 4.6.3 p1.11, pie-0.5.2) > COLLECT_GCC_OPTIONS='-march=native' '-mtune=native' '-v' '-E' > /usr/libexec/gcc/x86_64-pc-linux-gnu/4.6.3/cc1 -E -quiet -v - > -march=pentium-m -mcx16 -msahf -mno-movbe -mno-aes -mno-pclmul -mpopcnt > -mno-abm -mno-lwp -mno-fma -mno-fma4 -mno-xop -mbmi -mno-tbm -mno-avx > -mno-sse4.2 -mno-sse4.1 --param l1-cache-size=32 --param > l1-cache-line-size=64 --param l2-cache-size=4096 -mtune=generic > ignoring nonexistent directory "/usr/local/include" > ignoring nonexistent directory > "/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/../../../../x86_64-pc-linux-gnu/include" > > #include "..." search starts here: > #include <...> search starts here: > /usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/include > /usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/include-fixed > /usr/include > End of search list. > # 1 "<stdin>" > <stdin>:1:0: error: CPU you selected does not support x86-64 instruction > set > > It is returning pentium-m as architecture, which indeed is 32bit. I'm > presently running the VM with -march=core2, but this is very weird. > > This is the /proc/cpuinfo: > > processor : 0 > vendor_id : GenuineIntel > cpu family : 6 > model : 2 > model name : QEMU Virtual CPU version 1.0 > stepping : 3 > microcode : 0x1 > cpu MHz : 3399.998 > cache size : 4096 KB > fpu : yes > fpu_exception : yes > cpuid level : 4 > wp : yes > flags : fpu de pse tsc msr pae mce cx8 apic sep mtrr pge mca > cmov pse36 clflush mmx fxsr sse sse2 syscall nx lm rep_good nopl pni vmx > cx16 popcnt hypervisor lahf_lm > bogomips : 6799.99 > clflush size : 64 > cache_alignment : 64 > address sizes : 40 bits physical, 48 bits virtual > power management: > > Any idea what should be the march/mtune value? >
I don't have any experience with Hetzner's VMs - I only use their dedicated machines :) But as a more generic tip, you should install gentoo in VMs only with generic optimization. You can not safely rely on what CPU your VM will get. Maybe in 6 months the host your vm is on crashes, and your vm will be migrated to a new system with totally different cpu (actual hardware cpu or the cpu configuration that qemu is going to emulate).
