From: Davidlohr Bueso <dave@stgolabs.net>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Peter Zijlstra" <peterz@infradead.org>,
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>,
"Andr� Almeida" <andrealmeid@igalia.com>,
libc-alpha@sourceware.org, "Steven Rostedt" <rostedt@goodmis.org>,
"Jonathan Corbet" <corbet@lwn.net>,
"Florian Weimer" <fweimer@redhat.com>
Subject: Re: [RFC PATCH 1/4] rseq: Add sched_state field to struct rseq
Date: Wed, 17 May 2023 09:03:10 -0700 [thread overview]
Message-ID: <43ssw4ghx52wpw2klzyi35ioc4fr5g2givcc7sdxcyndytghsd@z4j6vdwvmn4d> (raw)
In-Reply-To: <20230517152654.7193-2-mathieu.desnoyers@efficios.com>
On Wed, 17 May 2023, Mathieu Desnoyers wrote:
>Expose the "on-cpu" state for each thread through struct rseq to allow
>adaptative mutexes to decide more accurately between busy-waiting and
>calling sys_futex() to release the CPU, based on the on-cpu state of the
>mutex owner.
Oh yeah moving the spin stuff out of the kernel is much nicer.
>It is only provided as an optimization hint, because there is no
>guarantee that the page containing this field is in the page cache, and
>therefore the scheduler may very well fail to clear the on-cpu state on
>preemption. This is expected to be rare though, and is resolved as soon
>as the task returns to user-space.
>
>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.
>
>Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
>Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
>Cc: Jonathan Corbet <corbet@lwn.net>
>Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
>Cc: Carlos O'Donell <carlos@redhat.com>
>Cc: Florian Weimer <fweimer@redhat.com>
>Cc: libc-alpha@sourceware.org
>---
> include/linux/sched.h | 12 ++++++++++++
> include/uapi/linux/rseq.h | 17 +++++++++++++++++
> kernel/rseq.c | 14 ++++++++++++++
> 3 files changed, 43 insertions(+)
Ie: previous efforts
kernel/futex.c | 675 ++++++++++++++++++++++++++++++++++++++------
kernel/futex.c | 572 ++++++++++++++++++++++++++++++++++++-------------
Thanks,
Davidlohr
next prev parent reply other threads:[~2023-05-17 16:36 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-17 15:26 [RFC PATCH 0/4] Extend rseq with sched_state field Mathieu Desnoyers
2023-05-17 15:26 ` [RFC PATCH 1/4] rseq: Add sched_state field to struct rseq Mathieu Desnoyers
2023-05-17 16:03 ` Davidlohr Bueso [this message]
2023-05-18 21:49 ` Boqun Feng
2023-05-19 14:15 ` Mathieu Desnoyers
2023-05-19 17:18 ` Boqun Feng
2023-05-23 14:10 ` Mathieu Desnoyers
2023-05-19 20:51 ` Noah Goldstein
2023-05-23 12:49 ` Mathieu Desnoyers
2023-05-23 16:32 ` Noah Goldstein
2023-05-23 17:30 ` Mathieu Desnoyers
2023-05-23 20:10 ` Noah Goldstein
2023-05-17 15:26 ` [RFC PATCH 2/4] selftests/rseq: Add sched_state rseq field and getter Mathieu Desnoyers
2023-05-28 14:04 ` kernel test robot
2023-05-17 15:26 ` [RFC PATCH 3/4] selftests/rseq: Implement sched state test program Mathieu Desnoyers
2023-05-17 15:26 ` [RFC PATCH 4/4] selftests/rseq: Implement rseq_mutex " Mathieu Desnoyers
2023-05-17 16:07 ` [RFC PATCH 0/4] Extend rseq with sched_state field Davidlohr Bueso
2023-05-17 18:36 ` Steven Rostedt
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