[Libvir] New (last ?) virtual cpu functions proposal
Jim Fehlig
jfehlig at novell.com
Wed Aug 2 23:46:57 UTC 2006
Thanks for the proposal! Just a few questions inline, otherwise looks
good for my use cases.
Philippe Berthault wrote:
> Here the new virtual cpu functions proposal.
> What do you think about it ?
>
>
>
> /**
> * *virVcpuInfo*: structure for information about a virtual CPU in a
> domain.
> */
> typedef enum {
> VIR_VCPU_OFFLINE = 0, /* the virtual CPU is offline */
> VIR_VCPU_RUNNING = 1, /* the virtual CPU is running */
> VIR_VCPU_BLOCKED = 2, /* the virtual CPU is blocked on
> resource */
> *} virVcpuState*;
>
> typedef struct _virVcpuInfo virVcpuInfo;
> struct _virVcpuInfo {
> unsigned int number; /* virtual CPU number */
> int state; /* value from virVcpuState */
> unsigned long long cpuTime; /* CPU time used, in nanoseconds */
> int cpu; /* real CPU number, or -1 if offline */
> };
> typedef virVcpuInfo **virVcpuInfoPtr*;
>
>
> /**
> * *virDomainSetVcpus*:
> * @*domain*: pointer to domain object, or NULL for Domain0
> * @*nvcpus*: the new number of virtual CPUs for this domain
> *
> * Dynamically change the number of virtual CPUs used by the domain.
> * Note that this call may fail if the underlying virtualization
> hypervisor
> * does not support it or if growing the number is arbitrary limited.
> * This function requires priviledged access to the hypervisor.
> *
> * Returns 0 in case of success, -1 in case of failure.
> */
> int *virDomainSetVcpus* (virDomainPtr domain,
> unsigned int nvcpus);
>
>
> /**
> * *virDomainPinVcpu*:
> * @*domain*: pointer to domain object, or NULL for Domain0
> * @*vcpu*: virtual CPU number
> * @*cpumap*: pointer to a bit map of real CPUs (in 8-bit bytes).
> * Each bit set to 1 means that corresponding CPU is usable.
> * Bytes are stored in little-endian order: CPU0-7, 8-15...
> * In each byte, lowest CPU number is least significant bit.
> * @*maplen*: number of bytes in cpumap, from 1 up to size of CPU map in
> * underlying virtualization system (Xen...).
> * If maplen < size, missing bytes are set to zero.
> * If maplen > size, failure code is returned.
> *
> * Dynamically change the real CPUs which can be allocated to a
> virtual CPU.
> * This function requires priviledged access to the hypervisor.
> *
> * Returns 0 in case of success, -1 in case of failure.
> */
> int *virDomainPinVcpu* (virDomainPtr domain,
> unsigned int vcpu,
> unsigned char *cpumap,
> int maplen);
>
How do I get the "size of CPU map in underlying virtualization system"
described in maplen comments?
> /* Macros for bit manipulation in cpumap */
> #define *USE_CPU*(cpumap,cpu) (cpumap[(cpu)/8] |= (1<<((cpu)%8)))
> #define *UNUSE_CPU*(cpumap,cpu) (cpumap[(cpu)/8] &= ~(1<<((cpu)%8)))
>
>
> /**
> * *virDomainGetVcpus*:
> * @*domain*: pointer to domain object, or NULL for Domain0
> * @*info*: pointer to an array of virVcpuInfo structures
> * @*maxinfo*: number of structures in info array
> * @*cpumaps*: pointer to a bit map of real CPUs for all vcpus of this
> domain.
> * If cpumaps is NULL, then no cpumap information is returned by
> the API.
> * It's assumed there is <maxinfo> cpumap in cpumaps.
> * The memory allocated to cpumaps must be (maxinfo * maplen) bytes.
> * One cpumap inside cupmaps have the format described in
> virDomainPinVcpu API.
> * @*maplen*: number of bytes in one cpumap, from 1 up to size of CPU
> map in
> * underlying virtualization system (Xen...).
> *
> * Extract information about virtual CPUs of domain, store it in info
> array.
> *
> * Returns the number of info filled in case of success, -1 in case of
> failure.
> */
> int *virDomainGetVcpus* (virDomainPtr domain,
> virVcpuInfoPtr info,
> int maxinfo,
> unsigned char *cpumaps, /* may be NULL */
> int maplen);
If there is no physical cpu affinity (e.g. the default - vcpus can float
among any pcpu), does each cpumap in cpumaps have all bits set? Do we
indicate no affinity by having all possible pcpus marked as bound?
>
> /* Macros for bit testing in cpumaps */
> #define *CPU_USABLE*(cpumaps,maplen,vcpu,cpu) \
> (cpumaps[((vcpu)*(maplen))+((cpu)/8)] & (1<<((cpu)%8)))
>
> /*
> * Macro for copying the cpumap of a vcpu from cupmaps inside a
> standalone cpumap.
> * This macro is useful in case of using virDomainPinVcpu() after
> virDomainGetVcpus().
> * cpumap must be previously allocated.
> */
> #define *COPY_CPUMAP*(cpumaps,maplen,vcpu,cpumap) \
> memcpy(cpumap, &(cpumaps[(vcpu)*(maplen)]), (maplen))
>
> ------------------------------------------------------------------------
>
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