Tags give the ability to mark specific points in history as being important
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wq-for-6.5-rc5-fixes
aa6fde93 · ·workqueue: Fixes for v6.5-rc5 Two commits: * The recently added cpu_intensive auto detection and warning mechanism was spuriously triggered on slow CPUs. While not causing serious issues, it's still a nuisance and can cause unintended concurrency management behaviors. Relax the threshold on machines with lower BogoMIPS. While BogoMIPS is not an accurate measure of performance by most measures, we don't have to be accurate and it has rough but strong enough correlation. * A correction in Kconfig help text.
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xfs-async-dio.6-2023-08-01
8c052fb3 · ·Improve iomap/xfs async dio write performance iomap always punts async dio write completions to a workqueue, which has a cost in terms of efficiency (now you need an unrelated worker to process it) and latency (now you're bouncing a completion through an async worker, which is a classic slowdown scenario). io_uring handles IRQ completions via task_work, and for writes that don't need to do extra IO at completion time, we can safely complete them inline from that. This patchset adds IOCB_DIO_CALLER_COMP, which an IO issuer can set to inform the completion side that any extra work that needs doing for that completion can be punted to a safe task context. The iomap dio completion will happen in hard/soft irq context, and we need a saner context to process these completions. IOCB_DIO_CALLER_COMP is added, which can be set in a struct kiocb->ki_flags by the issuer. If the completion side of the iocb handling understands this flag, it can choose to set a kiocb->dio_complete() handler and just call ki_complete from IRQ context. The issuer must then ensure that this callback is processed from a task. io_uring punts IRQ completions to task_work already, so it's trivial wire it up to run more of the completion before posting a CQE. This is good for up to a 37% improvement in throughput/latency for low queue depth IO, patch 5 has the details. If we need to do real work at completion time, iomap will clear the IOMAP_DIO_CALLER_COMP flag. This work came about when Andres tested low queue depth dio writes for postgres and compared it to doing sync dio writes, showing that the async processing slows us down a lot.