ngx_cpuinfo / kvm & qemu / ngx_cacheline_size

[Bertrand Paquet]

Hi,

I have virtual machine running on qemu / kvm.

cat /proc/cpuinfo give :
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 2
model name : QEMU Virtual CPU version 1.1.2
stepping : 3
microcode : 0x1
cpu MHz : 1999.999
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 up rep_good nopl pni cx16 popcnt
hypervisor lahf_lm
bogomips : 3999.99
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:

the code in ngx_cpuinfo use the model value (2), and set
the ngx_cacheline_size to 32, instead of 64 given by cache_alignment in
/proc/cpuinfo.

On same host using vmware virtualization, /proc/cpuinfo give a model of 45,
ngx_cacheline_size is set to 64.

I think I can have low performances problems due to the ngx_cacheline_size
of 32 under qemu virtualization. Do you confirm ?

Do you think we have to change ngx_cpuinfo code to give ngx_cacheline_size
64 on qemu env ?

Regards,

Bertrand
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