From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org,
"Thomas Gleixner" <tglx@linutronix.de>,
"Paul E . McKenney" <paulmck@kernel.org>,
"Boqun Feng" <boqun.feng@gmail.com>,
"H . Peter Anvin" <hpa@zytor.com>, "Paul Turner" <pjt@google.com>,
linux-api@vger.kernel.org,
"Christian Brauner" <brauner@kernel.org>,
"Florian Weimer" <fw@deneb.enyo.de>,
David.Laight@ACULAB.COM, carlos@redhat.com,
"Peter Oskolkov" <posk@posk.io>,
"Alexander Mikhalitsyn" <alexander@mihalicyn.com>,
"Chris Kennelly" <ckennelly@google.com>,
"Ingo Molnar" <mingo@redhat.com>,
"Darren Hart" <dvhart@infradead.org>,
"Davidlohr Bueso" <dave@stgolabs.net>,
"André Almeida" <andrealmeid@igalia.com>,
libc-alpha@sourceware.org, "Steven Rostedt" <rostedt@goodmis.org>,
"Jonathan Corbet" <corbet@lwn.net>,
"Noah Goldstein" <goldstein.w.n@gmail.com>,
"Daniel Colascione" <dancol@google.com>,
longman@redhat.com,
"Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>
Subject: [RFC PATCH v2 0/4] Extend rseq with sched_state_ptr field
Date: Mon, 29 May 2023 15:14:12 -0400 [thread overview]
Message-ID: <20230529191416.53955-1-mathieu.desnoyers@efficios.com> (raw)
This prototype extends struct rseq with a new sched_state_ptr field,
which points to a structure containing 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.
New in this v2:
- Introduce a "struct rseq_sched_state", which contains the on-cpu
scheduler flag and a thread ID field. This eliminates false sharing
on the struct rseq cache lines caused by busy-waiting.
I have favored adding a "thread ID" field to struct rseq_sched_state
rather than adding stores of owner pointer in addition to a
compare-and-swap and store on a uint32_t for lock state to minimize the
number of stores to perform on the fast-path.
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 | 16 +++
include/uapi/linux/rseq.h | 41 ++++++
kernel/rseq.c | 43 +++++++
tools/testing/selftests/rseq/.gitignore | 2 +
tools/testing/selftests/rseq/Makefile | 3 +-
tools/testing/selftests/rseq/rseq-abi.h | 42 ++++++
tools/testing/selftests/rseq/rseq.c | 13 ++
tools/testing/selftests/rseq/rseq.h | 5 +
tools/testing/selftests/rseq/rseq_mutex.c | 120 ++++++++++++++++++
.../testing/selftests/rseq/sched_state_test.c | 72 +++++++++++
10 files changed, 356 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
next reply other threads:[~2023-05-29 19:14 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-29 19:14 Mathieu Desnoyers [this message]
2023-05-29 19:14 ` [RFC PATCH v2 1/4] rseq: Add sched_state field to struct rseq Mathieu Desnoyers
2023-05-29 19:35 ` Florian Weimer
2023-05-29 19:48 ` Mathieu Desnoyers
2023-05-30 8:20 ` Florian Weimer
2023-05-30 14:25 ` Mathieu Desnoyers
2023-05-30 15:13 ` Mathieu Desnoyers
2023-09-26 20:52 ` Dmitry Vyukov
2023-09-26 23:49 ` Dmitry Vyukov
2023-09-26 23:54 ` Dmitry Vyukov
2023-09-27 4:51 ` Florian Weimer
2023-09-27 15:58 ` Dmitry Vyukov
2023-09-28 8:52 ` Florian Weimer
2023-09-28 14:44 ` Dmitry Vyukov
2023-09-28 14:47 ` Dmitry Vyukov
2023-09-28 10:39 ` Peter Zijlstra
2023-09-28 11:22 ` David Laight
2023-09-28 13:20 ` Mathieu Desnoyers
2023-09-28 14:26 ` Peter Zijlstra
2023-09-28 14:33 ` David Laight
2023-09-28 15:05 ` André Almeida
2023-09-28 14:43 ` Steven Rostedt
2023-09-28 15:51 ` David Laight
2023-10-02 16:51 ` Steven Rostedt
2023-10-02 17:22 ` David Laight
2023-10-02 17:56 ` Steven Rostedt
2023-09-28 20:21 ` Thomas Gleixner
2023-09-28 20:43 ` Mathieu Desnoyers
2023-09-28 20:54 ` Thomas Gleixner
2023-09-28 22:11 ` Mathieu Desnoyers
2023-05-29 19:14 ` [RFC PATCH v2 2/4] selftests/rseq: Add sched_state rseq field and getter Mathieu Desnoyers
2023-05-29 19:14 ` [RFC PATCH v2 3/4] selftests/rseq: Implement sched state test program Mathieu Desnoyers
2023-05-29 19:14 ` [RFC PATCH v2 4/4] selftests/rseq: Implement rseq_mutex " Mathieu Desnoyers
2023-09-28 19:55 ` Thomas Gleixner
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