On 05/29/2013 11:14 AM, Eric Blake wrote:
On 05/28/2013 08:53 PM, Guannan Ren wrote:
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There are little document about how to set values of sockets, cores, threads properly. After going through qemu code, I summarize the package/cores/threads/ algorithm which can be verified by 'cpuid' tool. The following only explains the case of all the four number are given in qemu commandline. smp = n (argument to -smp) nr_threads = smp / (cores * sockets) nr_cores = cores -smp 4, sockets=1,cores=4,threads=2 leads to: 1(physical cpu) *4(cores) *1(thread) One physical cpu contains four cores log processor which each contains one thread logical processor. 0 means only one physical cpu package pkg_id = cpu_index/nr_threads/nr_cores 0 = 0 / 1 / 4 0 = 1 / 1 / 4 0 = 2 / 1 / 4 0 = 3 / 1 / 4 3 means there are four multi-cores logical processor core_id = cpu_index/nr_threads % nr_cores 0 = 0 / 1 % 4 1 = 1 / 1 % 4 2 = 2 / 1 % 4 3 = 3 / 1 % 4 0 means only one thread logical processor smt_id = cpu_index % nr_threads 0 = 0 % 1 0 = 1 % 1 0 = 2 % 1 0 = 3 % 1 And the result could be verified by 'cpuid' tool running in fedora guest. 1st vcpu: (APIC synth): PKG_ID=0 CORE_ID=0 SMT_ID=0 2nd vcpu: (APIC synth): PKG_ID=0 CORE_ID=1 SMT_ID=0 3rd vcpu: (APIC synth): PKG_ID=0 CORE_ID=2 SMT_ID=0 4th vcpu: (APIC synth): PKG_ID=0 CORE_ID=3 SMT_ID=0 I tried it on several cpu topology: -smp 16, sockets=2,cores=2,threads=1 leads to 2 * 2 * 4 There are two physical cpu package. Each of them contains two cores logical processor and each of the cores contains four hyper-threading logical processor. The result could be verified by cpuid tool. If the calculation is true, I think my patch is self-acked. Guannan