SMP WG, February 21, 2023

--- title: "SMP WG, February 21, 2023" tags: unikraft, smp, synchronization datetime: 2023-02-21T14:30:00+02:00 location: Online, Discord (https://bit.ly/UnikraftDiscord), the `#monkey-business` voice channel teams: - smp participants: - Andra - Razvan V - Sairaj - Simon --- ## :dart: Agenda - Status update - Next steps ## :closed_book: Discussions AP: - Created doc for the SMP test plan: https://hackmd.io/@unikraft/BkQnu4bCs. - Did reviews for the [synchronization primitives](https://github.com/unikraft/unikraft/pull/476) and [virtio-net multiqueue support](https://github.com/unikraft/unikraft/pull/712) PRs. - Looking into how to adjust the scheduler to validate the synchronization primitives using a multi-core setup e.g. define [per-CPU variable(s) for the current thread](https://github.com/unikraft/unikraft/blob/staging/lib/uksched/sched.c#L46) (use CPU core ID as index in the array variable) and integrate it in the scheduler orchestration. RV: - Looked in the ukalloc buddy, trying to synchronize its implementation. - Started by using the spinlock. - Started to use malloc with different CPU cores. - Could I start with uktest? - Can start with ukalloc buddy main one. - When should check the state? After allocation and memory setup ... Simon K: - Could alloc, free, alloc, free, and check for failures. - Can increase, decrease memory size, free, can run on different CPUs. - Can also have unit tests eventually. - Could check each allocation is not overllaping. - Could check free memory, if also makes sense. - Could do massive allocs of different size, if free operations works. - Could develop 2 types of test suites: for the generic one ukalloc, and per each memory allocator, based also on the internals e.g. metadata. - Could check for overlapping regios when using multiple cores. - Check pair-wise the memory size on the same CPU and different ones. - The testing setup could crash (e.g. invalid metadata) or could fail. Sairaj K: - Created a [PR for SMP-safe virtio-net](https://github.com/unikraft/unikraft/pull/759). - Try to break the virtio-net for SMP. - Trying to send data on the same queue using different processors. - Run http-reply application, but not using SMP, so just checks it is not breaking with these changes. Simon K: - Do you use the uknetdev for SMP checks? - Should use this for testing. Sairaj K: - Yes, I use the gen packet app one. - Could use tap or bridge for this setup. (Discord reference for the previous discussion on this topic: https://discord.com/channels/762976922531528725/883603425076584448/1062596440507023390) - Can send traffic to a local application on my system. Simon K: - Can pick traffic on the other guest, setup 2 VMs. - Could read about macvtap mode, get network access without passthrough to guest. - Thinking how to test virtio multiqueue on the receive side. Sairaj K: - Can take a look at core libraries, to check for synchronization. - Marc suggested to take a look into TLS for SMP. - Could also look into the sched / thread part of uksched. Simon K: - Can use cooperative scheduler for a testing setup with one scheduler per CPU. - Can also schedule a thread for pinning to a certain CPU, migrate threads between schedulling instances. - Then can setup schedulers per multiple CPUs. - Can check ukboot for CPU scheduling, provide a function for the SMP API, use sched register. - Create a thread on CPU A and assign it to CPU B, need spinlock for the API. - Make the library ecosystem work with SMP e.g. vfscore. - Also can check the posix libraries, lwip for SMP-safe setup. ## :wrench: TODOs and Decisions - Add uklock library to the CI system configuration. This is needed for the [synchronization primitives PR](https://github.com/unikraft/unikraft/pull/476). Discord channel discussion: https://discord.com/channels/762976922531528725/857972234201858099/1073559322841329674. - AP: - Adjust the scheduler to validate the synchronization primitives using a multi-core setup e.g. define [per-CPU variable(s) for the current thread](https://github.com/unikraft/unikraft/blob/staging/lib/uksched/sched.c#L46) (use CPU core ID as index in the array variable) and integrate it in the scheduler orchestration - Complete the first round of review for the virtio-net multiqueue support PR. - Create a list of Unikraft components e.g. libraries, that need synchronization in a multi-core environment. Then we can discuss in the SMP community meeting about priorities and dependencies. - RV: - Identify test cases / failures and necessary synchronization for the ukalloc buddy. - Sairaj K: - Develop a testing setup for the virtio-net multiqueue support when using multiple cores. - Help with the synchronization primitives validation. - Can then take a look at Unikraft core libraries, to check for necessary synchronization.