I hope I will find a way to post the patches prepared by Michel Ponceau before the end of the week. Jean-Paul <table width=100%> <tr valign=top> <td> <td>"Daniel P. Berrange" <berrange@redhat.com> Envoyé par : libvir-list-bounces@redhat.com 29/07/2006 09:35 Veuillez répondre à "Daniel P. Berrange" <td> Pour : Jim Fehlig <jfehlig@novell.com> cc : libvir-list@redhat.com Objet : Re: [Libvir] Re: Proposal : add 3 functions to Libvirt API, for virtual CPUs</table> On Fri, Jul 28, 2006 at 03:18:17PM -0600, Jim Fehlig wrote: > Has any progress been made on this proposal? I don't see anything in > current CVS. This functionality would be useful for Xen-CIM project. IIRC Michel Ponceau might have started on some prototype code, but he didn't post it to the list yet & is apparently on vacation for another couple of weeks (according to his email auto-responder). If no one else has started work on it in the meantime, I'm planning to get working on it when I return from vacation Aug 4th since I also need it for the virt-manager application. Regards, Dan. > michel.ponceau@bull.net wrote: > > > >Corrections on proposal: > >1) PinVcpus > >Replace: > > * @cpumap: pointer to a bit map of real CPUs (format in virVcpuInfo) > >* @maplen: length of cpumap, in 8-bit bytes > >by: > > * @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. > > > >2) GetVcpu > >Add 4rth argument: > > * @maplen: number of bytes in cpumap field of virVcpuInfo > >virDomainGetVcpus(virDomainPtr domain, virVcpuInfoPtr info, int > >maxinfo, int maplen) > > > >3) Structure VcpuInfo > >Suppress: #define VIR_MAX_CPUS 256 > >Replace: > > unsigned char cpumap[VIR_MAX_CPUS/8]; /* Bit map of usable real CPUs. > >by: > > unsigned char cpumap[]; /* Bit map of usable real CPUs. > > Variable length: it may be less or greater than size of CPU > >map in > > underlying virtualization system (Xen...). > > > >4) Accessor macros: to be defined later. > > > >Veuillez répondre à veillard@redhat.com > > > >Pour : michel.ponceau@bull.net > >cc : libvir-list@redhat.com > >Objet : Re: Proposal : add 3 functions to Libvirt API, for > >virtual CPUs > > > >On Fri, Jun 30, 2006 at 04:00:45PM +0200, michel.ponceau@bull.net wrote: > >> For our administration, we need the following actions, while concerned > >> domain is running: > >> 1) Change the number of virtual CPUs. > >> 2) Change the pinning (affinity) of a virtual CPU on real CPUs. > >> 3) Get detailed information for each virtual CPU. > >> Currently there is no Libvirt function provided for that. We suggest to > >> add the following 3 functions (in libvirt.c): > >> /** > >> * 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) > > > > okay > > > >> /** > >> * virDomainPinVcpu: > >> * @domain: pointer to domain object, or NULL for Domain0 > >> * @vcpu: virtual CPU number > >> * @cpumap: pointer to a bit map of real CPUs (format in virVcpuInfo) > >> * @maplen: length of cpumap, in 8-bit bytes > >> * > >> * 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) > > > > Can you explain more clearly what is the format of cpumap ? An example > >would be welcome, and that would be needed for the doc and maybe testing. > >What would happen if maplen is < or > than the number of CPU divided > >by 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 > >> * > >> * Extract information about virtual CPUs of a 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) > > > > Hum ... now the problem with that API entry point is that we 'burn' the > >maximum 256 processors in the ABI, i.e. if we ever need to go past 256 > >client and servers need to be recompiled. Maybe this is not a real problem > >in practice but that's annoying. Is there existing APIs doing this kind > >of things (in POSIX for example), and what hard limit did they use ? > > Maybe > > int virDomainGetVcpusNr(virDomainPtr domain, int nr, virVcpuInfoPtr info, > > int maxCPU); > >Where the maxCPU is defined by the client as the number of real CPU > >it defined in its virVcpuInfoPtr and then an iteration over the virtual > >CPU defined in the domain is possible too. > >Of course if the domain uses many virtual CPUs this would become expensive > >but somehow I don't see that being the common use, I would rather guess > >the domains created use a few CPUs even if instantiated on a very > >large machine. > >This > > > > > >> with the following structure (in libvirt.h): > >> /** > >> * virVcpuInfo: structure for information about a virtual CPU in a > >domain. > >> */ > >> #define VIR_MAX_CPUS 256 > > > > Hum, there is already NUMA machines with more than 256 processors, > >it's annoying to define an API limit when you know it is already > >breakable. > > > >> 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 */ > >> unsigned char cpumap[VIR_MAX_CPUS/8]; /* Bit map of usable real > >CPUs. > >> 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 > >> */ > >> }; > >> typedef virVcpuInfo *virVcpuInfoPtr; > > > > Hum, maybe some accessors should be provided in the API, letting the > >client > >code handle access and having to take care of indianness issues > >doesn't feel > >very nice. Something like the FD_CLR/FD_ISSET/FD_SET/FD_ZERO equivalents > >when using the select() POSIx call. > > > >> I have successfully tried those functions via Xen hypervisor, except > >for > >> the first (SetVcpus) where hypervisor operation DOM0_MAX_VCPUS fails > >> (maybe it is not possible on a running domain ?). That function was > >> successful via Xen daemon. > > > >Maybe that operation requires more than one hypervisor call to > >actually enable > >the processors. The simpler would be to look at the code in xend about > >what's > >needed there, maybe the kernel need to be made aware of that and I > >would expect > >this to be a xenstore operation. > >At least we know we can fallback to xend if the hypervisor call > >doesn't work > >directly. > >I don't know if virDomainGetVcpus should really be mutated into > >virDomainGetVcpusNr, I would certainly like to be able to keep that API > >extensible for more than 256 CPUs. Maybe I'm just too cautious there, > > > > I would really like feedback from others on this issue ! > >In the meantime sending the current set of patches you developped could > >allow to look closely at the 2 calls that I feel okay with. > > > > thanks and sorry it took so long ! > > > >Daniel > > > >-- > >Daniel Veillard | Red Hat http://redhat.com/ > >veillard@redhat.com | libxml GNOME XML XSLT toolkit http://xmlsoft.org/ > >http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/ > > > >------------------------------------------------------------------------ > > > >-- > >Libvir-list mailing list > >Libvir-list@redhat.com > >https://www.redhat.com/mailman/listinfo/libvir-list > > > > -- > Libvir-list mailing list > Libvir-list@redhat.com > https://www.redhat.com/mailman/listinfo/libvir-list -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=| -- Libvir-list mailing list Libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list