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Bug 1680956

Summary: backport rx/tx epic from OSP 14
Product: Red Hat OpenStack Reporter: mgeary <mgeary>
Component: documentationAssignee: mgeary <mgeary>
Status: CLOSED WONTFIX QA Contact: RHOS Documentation Team <rhos-docs>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 12.0 (Pike)CC: dcadzow
Target Milestone: ---Keywords: Triaged
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Hardware: Unspecified   
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Last Closed: 2019-02-28 14:03:11 UTC Type: Bug
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 1512941, 1674553    
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Description mgeary 2019-02-25 15:02:39 UTC 
Virtual CPUs (vCPUs) can be preempted by the hypervisor kernel thread even with strong partitioning in place (isolcpus, tuned). Preemptions are not frequent, a few per second, but with 256 descriptors per virtio queue, just one preemption of the vCPU can lead to packet drop, because the 256 slots are filled during the preemption. This is the case for network functions virtualization (NFV) VMs in which the per queue packet rate is above 1 Mpps (1 million packets per second).

This release supports two new tunable options: 'rx_queue_size' and 'tx_queue_size'. Use these options to configure the RX queue size and TX queue size of virtio NICs, respectively, to reduce packet drop.