[libvirt] [PATCH v4 5/9] Implement public API for getting/setting specific IOThread pinning

[Daniel P. Berrange]

On Thu, Mar 05, 2015 at 09:03:02PM -0500, John Ferlan wrote:
> Add virDomainGetIOThreadPin to fetch the pinned CPU affinity map
> for one IOThread.
> 
> Add virDomainPinIOThread to allow setting the CPU affinity for a
> specific IOThread.
> 
> Signed-off-by: John Ferlan <jferlan at redhat.com>
> ---
>  include/libvirt/libvirt-domain.h |  10 +++
>  src/driver-hypervisor.h          |  16 +++++
>  src/libvirt-domain.c             | 152 +++++++++++++++++++++++++++++++++++++++
>  src/libvirt_public.syms          |   2 +
>  4 files changed, 180 insertions(+)
> 
> diff --git a/include/libvirt/libvirt-domain.h b/include/libvirt/libvirt-domain.h
> index 9487b80..fc35cd2 100644
> --- a/include/libvirt/libvirt-domain.h
> +++ b/include/libvirt/libvirt-domain.h
> @@ -1609,6 +1609,16 @@ void                 virDomainIOThreadsInfoFree(virDomainIOThreadInfoPtr info);
>  int                  virDomainGetIOThreadsInfo(virDomainPtr domain,
>                                                 virDomainIOThreadInfoPtr **info,
>                                                 unsigned int flags);
> +int                  virDomainGetIOThreadPin (virDomainPtr domain,
> +                                              unsigned int iothread_id,
> +                                              unsigned char *cpumap,
> +                                              int maplen,
> +                                              unsigned int flags);

Isn't the GetIOThreadsInfo method & struct already reporting the pinning
info for all current IO threads ? I'm not sure what the difference is
between what  GetIOThreadsInfo and GetIOThreadPin is ?

  +struct _virDomainIOThreadInfo {
  +    unsigned int iothread_id;          /* IOThread ID */
  +    unsigned char *cpumap;             /* CPU map for thread. A pointer to an */
  +                                       /* array of real CPUs (in 8-bit bytes) */
  +    int cpumaplen;                     /* cpumap size */
  +};

These fields match all the parameters in GetIOThreadPin, so it seems adding a
GetIOThreadPin is redundant,


> +int                  virDomainPinIOThread(virDomainPtr domain,
> +                                          unsigned int iothread_id,
> +                                          unsigned char *cpumap,
> +                                          int maplen,
> +                                          unsigned int flags);

This is fine though


> +/**
> + * virDomainPinIOThread:
> + * @domain: a domain object
> + * @iothread_id: either the thread_id to modify or a count of IOThreads
> + *      to be added or removed from the domain depending on the @flags setting

This can be updated now.

> + * @cpumap: pointer to a bit map of real CPUs (in 8-bit bytes) (IN)
> + *      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.
> + * @flags: bitwise-OR of virDomainModificationImpact
> + *
> + * Dynamically change the real CPUs which can be allocated to an IOThread.
> + * This function may require privileged access to the hypervisor.
> + *
> + * @flags may include VIR_DOMAIN_AFFECT_LIVE or VIR_DOMAIN_AFFECT_CONFIG.
> + * Both flags may be set.
> + * If VIR_DOMAIN_AFFECT_LIVE is set, the change affects a running domain
> + * and may fail if domain is not alive.
> + * If VIR_DOMAIN_AFFECT_CONFIG is set, the change affects persistent state,
> + * and will fail for transient domains. If neither flag is specified (that is,
> + * @flags is VIR_DOMAIN_AFFECT_CURRENT), then an inactive domain modifies
> + * persistent setup, while an active domain is hypervisor-dependent on whether
> + * just live or both live and persistent state is changed.
> + * Not all hypervisors can support all flag combinations.
> + *
> + * See also virDomainGetIOThreadsInfo for querying this information.
> + *
> + * Returns 0 in case of success, -1 in case of failure.
> + */
> +int
> +virDomainPinIOThread(virDomainPtr domain,
> +                     unsigned int iothread_id,
> +                     unsigned char *cpumap,
> +                     int maplen,
> +                     unsigned int flags)
> +{
> +    virConnectPtr conn;
> +
> +    VIR_DOMAIN_DEBUG(domain, "iothread_id=%u, cpumap=%p, maplen=%d",
> +                     iothread_id, cpumap, maplen);
> +
> +    virResetLastError();
> +
> +    virCheckDomainReturn(domain, -1);
> +    conn = domain->conn;
> +
> +    virCheckReadOnlyGoto(conn->flags, error);
> +    if ((unsigned short) iothread_id != iothread_id) {
> +        virReportError(VIR_ERR_OVERFLOW, _("input too large: %u"),
> +                       iothread_id);
> +        goto error;
> +    }
> +    virCheckPositiveArgGoto(iothread_id, error);
> +    virCheckNonNullArgGoto(cpumap, error);
> +    virCheckPositiveArgGoto(maplen, error);
> +
> +    if (conn->driver->domainPinIOThread) {
> +        int ret;
> +        ret = conn->driver->domainPinIOThread(domain, iothread_id,
> +                                              cpumap, maplen, flags);
> +        if (ret < 0)
> +            goto error;
> +        return ret;
> +    }
> +
> +    virReportUnsupportedError();
> +
> + error:
> +    virDispatchError(domain->conn);
> +    return -1;
> +}

Regards,
Daniel
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