On 04.06.2015 14:45, Nikolay Shirokovskiy wrote: > Statistics provided through PCS SDK. As we have only async interface in SDK we > need to be subscribed to statistics in order to get it. Trivial solution on > every stat request to subscribe, wait event and then unsubscribe will lead to > significant delays in case of a number of successive requests, as the event > will be delivered on next PCS server notify cycle. On the other hand we don't > want to keep unnesessary subscribtion. So we take an hibrid solution to > subcsribe on first request and then keep a subscription while requests are > active. We populate cache of statistics on subscribtion events and use this > cache to serve libvirts requests. > > * Cache details. > Cache is just handle to last arrived event, we call this cache > as if this handle is valid it is used to serve synchronous > statistics requests. We use number of successive events count > to detect that user lost interest to statistics. We reset this > count to 0 on every request. If more than PARALLELS_STATISTICS_DROP_COUNT > successive events arrive we unsubscribe. Special value of -1 > of this counter is used to differentiate between subscribed/unsubscribed state > to protect from delayed events. > > Values of RALLELS_STATISTICS_DROP_COUNT and PARALLELS_STATISTICS_TIMEOUT are > just drop-ins, choosen without special consideration. > > * Thread safety issues > Use parallelsDomObjFromDomainRef in parallelsDomainBlockStats as > we could wait on domain lock down on stack in prlsdkGetStatsParam > and if we won't keep reference we could get dangling pointer > on return from wait. > > Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@xxxxxxxxxxxxx> > --- > src/parallels/parallels_driver.c | 106 ++++++++++++++++++++++ > src/parallels/parallels_sdk.c | 183 ++++++++++++++++++++++++++++++++++++++ > src/parallels/parallels_sdk.h | 2 + > src/parallels/parallels_utils.c | 28 ++++++ > src/parallels/parallels_utils.h | 18 ++++ > 5 files changed, 337 insertions(+), 0 deletions(-) > Need more checks in case of unsuccessful unsubscribe, will resend. -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list