Messages in this thread | | | From | Mathieu Desnoyers <> | Subject | [RFC PATCH 0/4] Extend rseq with sched_state field | Date | Wed, 17 May 2023 11:26:50 -0400 |
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This prototype extends struct rseq with a new sched_state field, which contains a "on-cpu" flag kept up-to-date by the scheduler.
It is meant to be used by userspace adaptative mutexes to decide between busy-wait and futex wait system call (releasing the CPU) behaviors based on the current state of the mutex owner.
The goal is to improve use-cases where the duration of the critical sections for a given lock follows a multi-modal distribution, preventing statistical guesses from doing a good job at choosing between busy-wait and futex wait behavior.
This is in response to the LWN coverage of 2023 Open Source Summit North America (https://lwn.net/Articles/931789/) unscheduled slot "Adaptive spinning in user space" presented by André Almeida.
Feedback is welcome!
Mathieu
Mathieu Desnoyers (4): rseq: Add sched_state field to struct rseq selftests/rseq: Add sched_state rseq field and getter selftests/rseq: Implement sched state test program selftests/rseq: Implement rseq_mutex test program
include/linux/sched.h | 12 ++ include/uapi/linux/rseq.h | 17 +++ kernel/rseq.c | 14 ++ tools/testing/selftests/rseq/.gitignore | 2 + tools/testing/selftests/rseq/Makefile | 3 +- tools/testing/selftests/rseq/rseq-abi.h | 17 +++ tools/testing/selftests/rseq/rseq.h | 5 + tools/testing/selftests/rseq/rseq_mutex.c | 120 ++++++++++++++++++ .../testing/selftests/rseq/sched_state_test.c | 71 +++++++++++ 9 files changed, 260 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/rseq/rseq_mutex.c create mode 100644 tools/testing/selftests/rseq/sched_state_test.c
-- 2.25.1
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