Bug 1940346
| Summary: | [OVN-SCALE] OVN: Optimize trivial logical flow to OF rule translation. | ||||||
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| Product: | Red Hat Enterprise Linux Fast Datapath | Reporter: | Dumitru Ceara <dceara> | ||||
| Component: | ovn2.13 | Assignee: | OVN Team <ovnteam> | ||||
| Status: | CLOSED WONTFIX | QA Contact: | Jianlin Shi <jishi> | ||||
| Severity: | medium | Docs Contact: | |||||
| Priority: | low | ||||||
| Version: | FDP 20.H | CC: | ctrautma, jishi, mmichels, ralongi | ||||
| Target Milestone: | --- | ||||||
| Target Release: | --- | ||||||
| Hardware: | Unspecified | ||||||
| OS: | Unspecified | ||||||
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| Fixed In Version: | Doc Type: | If docs needed, set a value | |||||
| Doc Text: | Story Points: | --- | |||||
| Clone Of: | Environment: | ||||||
| Last Closed: | 2024-02-14 21:12:31 UTC | Type: | Bug | ||||
| Regression: | --- | Mount Type: | --- | ||||
| Documentation: | --- | CRM: | |||||
| Verified Versions: | Category: | --- | |||||
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |||||
| Cloudforms Team: | --- | Target Upstream Version: | |||||
| Embargoed: | |||||||
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This issue is being closed as an automatic process due to the issue's age. If you wish to re-open this issue, please do so in Jira (https://issues.redhat.com) in the 'FDP' project. Please be sure to set the component to the latest OVN version where this issue is known to occur. If this is a feature request or improvement, please set the component to 'OVN'. |
Created attachment 1764301 [details] OVN NB sample database. Description of problem: In large scale deployments OVN topologies usually consist of a large number of logical switches/routers. The logical flow pipelines for logical datapaths have a number of common flows (trivial flows) that are identical across all datapaths and usually just advance to the next table in the pipeline. Currently, with logical_dp_groups enabled, all these flows are associated to a datapath group that consists of all logical switches/routers. However, ovn-controller, when generating OF rules, expands the trivial logical flow applied on a datapath group with N datapaths into N individual openflows, prepending the "metadata=<datapath-key>" match to each of the openflows. For example, with the attached OVN NB database (from a scale test run), ovn-controller generates ~400K openflows on a single hypervisor. Changing ovn-controller to not match on logical datapath key for trivial flows could reduce the number of openflows to ~200K. Potential implementation: - extend the Logical_DP_Group SB schema to add a column to allow specifying if the datapath group consists of all switches/routers in the topology. - in the first stage of the switch/router pipeline store in the "flags" logical register a bit to indicate that the packet is processed on a switch or router pipeline. - when processing logical flows applied to datapath groups, if the group includes all switches, instead of generating N OF rules, one for each datapath in the group, generate a single OF rule with an additional match on the "flags" register bit that indicates that the packet is processed on the switch pipeline. - similarly, OF rules can be optimized for trivial logical flows applied to logical routers. Initial scale tests show an improvement of ~8% in time it takes to bring up an OVN node with an OpenShift-like deployment. This is explained by the fact that ovn-controller spends constant time in generating trivial flows.