What you’ve written is a best an oversimplification. It’s not correct to say that vpp lacks lockless data structures, and that all table-programming activities require coarse-grained locking and/or barrier synchronization.
Rather than starting a discussion from first principles, would it be possible to describe what you’re trying to do in detail? Thanks... Dave From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Satya Murthy Sent: Tuesday, August 13, 2019 10:51 AM To: vpp-dev@lists.fd.io Subject: [vpp-dev] lockless architecture Hi , Need some inputs on the lock less architecture with multi-threaded VPP system. From the experiences we had so far, taking a lock ( whatsoever small time the lock is taken for ) degrades the performance. Hence, trying to see if we have any feasibility of lockless architecture in VPP. We have gone through this in deep but seeing few issues on implementing this. 1) The vnet library and other core plugins like acls/classifiers does not seem to be thread-safe. The data structures in these does not seem be be thread specific, and hence applications from different threads may not able to modify them without acquiring a lock. This poses an issue. 2) I think, this is the reason, the control plane operations via vpp-api are handled by single main thread. However, this model will have an issue of main thread needing to take a write-lock when it is trying to modify any data via control plane. Worker threads during this time have to wait for this lock causing performance degradation. So, if both controlplane and data plane operations are performed by same thread (let's say by a specific worker), then we have an issue of underlying vnet layer not being thread-safe. If go with the approach of main thread and worker thread handling control and data plane activities respectively, then we need to take lock which may degrade performance. Any viable approach that can avoid both of these issues ? -- Thanks & Regards, Murthy
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