Message ID | 20230517152654.7193-1-mathieu.desnoyers@efficios.com |
---|---|
Headers | show |
Series | Extend rseq with sched_state field | expand |
+Cc Waiman. On Wed, 17 May 2023, Mathieu Desnoyers wrote: >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 >
On Wed, 17 May 2023 11:26:50 -0400 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote: > 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. Woot! I'm so glad I talked Jon into hanging around for André's spurious talk. He's the one that brought up rseq (as he mentioned in his article), and I guess you read that :-) Unfortunately, I'm in the process of a lot of trips and meetings/presentations over the next few weeks, and I will not be able to look into this. But I hope that André could test it out. Cheers! -- Steve