On Thu, Mar 19, 2015 at 01:08:22PM -0400, John Ferlan wrote:
Add virDomainIOThreadsSet to allow setting the number of IOThreads for a domain.
The API supports updating both the --live domain and the --config data.
Signed-off-by: John Ferlan <jferlan@redhat.com> --- include/libvirt/libvirt-domain.h | 3 ++ src/driver-hypervisor.h | 6 ++++ src/libvirt-domain.c | 60 ++++++++++++++++++++++++++++++++++++++++ src/libvirt_public.syms | 1 + 4 files changed, 70 insertions(+)
This one has been siting there for a while, I'll think out loud just to get a discussion going.
--- a/src/libvirt-domain.c +++ b/src/libvirt-domain.c @@ -8042,6 +8042,66 @@ virDomainPinIOThread(virDomainPtr domain,
/** + * virDomainSetIOThreads: + * @domain: pointer to domain object + * @niothreads: the new number of IOThreads for this domain + * @flags: bitwise-OR of virDomainModificationImpact + * + * Dynamically change the number of IOThreads used by the domain. + * Note that this call faiy fail if the underlying virtualization hypervisor + * does not support it or if growing the number is arbitrarily limited. + * This function may require privileged access to the hypervisor. + * + * @flags may include VIR_DOMAIN_AFFECT_LIVE to affect a running + * domain (which may fail if domain is not active), or + * VIR_DOMAIN_AFFECT_CONFIG to affect the next boot via the XML + * description of the domain. Both flags may be set. + * 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. + * + * Returns 0 in case of success, -1 in case of failure. + */ +int +virDomainSetIOThreads(virDomainPtr domain, + unsigned int niothreads, + unsigned int flags) +{
This seems ok for the use case where we just give a domain a few iothreads and all the disks will share them. But if you go for one iothread per disk, creating holes in iothread indexes could make sense - we allow unplugging disks from the middle. I can't think of a case where hotplugging a thread with id=6 would be useful if there are only 3 threads. Maybe there should be separate APIs for adding and deleting threads? Jan