From: Peter Zijlstra <peterz@infradead.org>
To: Daniel Colascione <dancol@google.com>
Cc: mathieu.desnoyers@efficios.com, paulmck@linux.vnet.ibm.com,
boqun.feng@gmail.com, luto@amacapital.net, davejwatson@fb.com,
linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
pjt@google.com, Andrew Morton <akpm@linux-foundation.org>,
linux@arm.linux.org.uk, tglx@linutronix.de, mingo@redhat.com,
hpa@zytor.com, Andrew Hunter <ahh@google.com>,
andi@firstfloor.org, cl@linux.com, bmaurer@fb.com,
rostedt@goodmis.org, josh@joshtriplett.org,
torvalds@linux-foundation.org, catalin.marinas@arm.com,
will.deacon@arm.com, mtk.manpages@gmail.com,
Joel Fernandes <joelaf@google.com>
Subject: Re: [RFC PATCH for 4.18 00/14] Restartable Sequences
Date: Wed, 2 May 2018 19:22:18 +0200 [thread overview]
Message-ID: <20180502172218.GL12180@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAKOZuesa338sc_=w6-wvro25idrSN_zx_zrHFyo-bDiORs7FZw@mail.gmail.com>
On Wed, May 02, 2018 at 03:53:47AM +0000, Daniel Colascione wrote:
> Suppose we make a userspace mutex implemented with a lock word having three
> bits: acquired, sleep_mode, and wait_pending, with the rest of the word not
> being relevant at the moment.
So ideally we'd kill FUTEX_WAIT/FUTEX_WAKE for mutexes entirely, and go
with FUTEX_LOCK/FUTEX_UNLOCK that have the same semantics as the
existing FUTEX_LOCK_PI/FUTEX_UNLOCK_PI, namely, the word contains the
owner TID.
As brought up in the last time we talked about spin loops, why do we
care if the spin loop is in userspace or not? Aside from the whole PTI
thing, the syscall cost was around 150 cycle or so, while a LOCK CMPXCHG
is around 20 cycles. So ~7 spins gets you the cost of entry.
next prev parent reply other threads:[~2018-05-02 17:22 UTC|newest]
Thread overview: 105+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-30 22:44 [RFC PATCH for 4.18 00/14] Restartable Sequences Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 01/14] uapi headers: Provide types_32_64.h (v2) Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 02/14] rseq: Introduce restartable sequences system call (v13) Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-05-16 16:24 ` Peter Zijlstra
2018-05-16 16:24 ` Peter Zijlstra
2018-05-16 20:18 ` Mathieu Desnoyers
2018-05-16 20:18 ` Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 03/14] arm: Add restartable sequences support Mathieu Desnoyers
2018-05-16 16:18 ` Peter Zijlstra
2018-05-16 16:18 ` Peter Zijlstra
2018-05-16 20:13 ` Mathieu Desnoyers
2018-05-16 20:13 ` Mathieu Desnoyers
2018-05-17 13:32 ` Will Deacon
2018-05-17 13:32 ` Will Deacon
2018-05-17 15:30 ` Mathieu Desnoyers
2018-05-17 15:30 ` Mathieu Desnoyers
2018-05-22 18:19 ` Mathieu Desnoyers
2018-05-22 18:19 ` Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 04/14] arm: Wire up restartable sequences system call Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 05/14] x86: Add support for restartable sequences (v2) Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 06/14] x86: Wire up restartable sequence system call Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 07/14] powerpc: Add support for restartable sequences Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-05-16 16:18 ` Peter Zijlstra
2018-05-16 16:18 ` Peter Zijlstra
2018-05-16 20:13 ` Mathieu Desnoyers
2018-05-16 20:13 ` Mathieu Desnoyers
2018-05-17 1:19 ` Boqun Feng
2018-05-17 1:19 ` Boqun Feng
2018-05-17 1:19 ` Boqun Feng
2018-05-17 7:43 ` Peter Zijlstra
2018-05-17 7:43 ` Peter Zijlstra
2018-05-17 15:28 ` Mathieu Desnoyers
2018-05-17 15:28 ` Mathieu Desnoyers
2018-05-17 23:50 ` Boqun Feng
2018-05-17 23:50 ` Boqun Feng
2018-05-18 18:17 ` Mathieu Desnoyers
2018-05-18 18:17 ` Mathieu Desnoyers
2018-05-20 14:08 ` Boqun Feng
2018-05-20 14:08 ` Boqun Feng
2018-05-20 14:08 ` Boqun Feng
2018-05-23 20:14 ` Mathieu Desnoyers
2018-05-23 20:14 ` Mathieu Desnoyers
2018-05-23 20:46 ` Paul E. McKenney
2018-05-23 20:46 ` Paul E. McKenney
2018-05-23 21:29 ` Mathieu Desnoyers
2018-05-23 21:29 ` Mathieu Desnoyers
2018-05-24 1:03 ` Michael Ellerman
2018-05-24 1:03 ` Michael Ellerman
2018-05-28 7:00 ` Mathieu Desnoyers
2018-05-28 7:00 ` Mathieu Desnoyers
2018-05-18 12:38 ` Michael Ellerman
2018-05-18 12:38 ` Michael Ellerman
2018-04-30 22:44 ` [PATCH 08/14] powerpc: Wire up restartable sequences system call Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 09/14] selftests: lib.mk: Introduce OVERRIDE_TARGETS Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-04-30 22:44 ` mathieu.desnoyers
2018-04-30 22:44 ` [PATCH 10/14] rseq: selftests: Provide rseq library (v5) Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-04-30 22:44 ` mathieu.desnoyers
2018-04-30 22:44 ` [PATCH 11/14] rseq: selftests: Provide basic test Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-04-30 22:44 ` mathieu.desnoyers
2018-04-30 22:44 ` [PATCH 12/14] rseq: selftests: Provide basic percpu ops test (v2) Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-04-30 22:44 ` mathieu.desnoyers
2018-04-30 22:44 ` [PATCH 13/14] rseq: selftests: Provide parametrized tests (v2) Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-04-30 22:44 ` mathieu.desnoyers
2018-04-30 22:44 ` [PATCH 14/14] rseq: selftests: Provide Makefile, scripts, gitignore (v2) Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-04-30 22:44 ` Mathieu Desnoyers
2018-04-30 22:44 ` mathieu.desnoyers
2018-05-02 3:53 ` [RFC PATCH for 4.18 00/14] Restartable Sequences Daniel Colascione
2018-05-02 8:43 ` Peter Zijlstra
2018-05-02 16:03 ` Mathieu Desnoyers
2018-05-02 16:03 ` Mathieu Desnoyers
2018-05-02 16:07 ` Daniel Colascione
2018-05-02 16:42 ` Steven Rostedt
2018-05-02 16:55 ` Daniel Colascione
2018-05-03 16:12 ` Mathieu Desnoyers
2018-05-03 16:12 ` Mathieu Desnoyers
2018-05-03 16:22 ` Daniel Colascione
2018-05-03 18:04 ` Mathieu Desnoyers
2018-05-03 18:04 ` Mathieu Desnoyers
2018-05-03 16:48 ` Joel Fernandes
2018-05-03 17:18 ` Daniel Colascione
2018-05-03 17:46 ` Joel Fernandes
2018-05-03 17:46 ` Joel Fernandes
2018-05-04 22:17 ` Ben Maurer
2018-05-04 22:17 ` Ben Maurer
2018-05-02 17:22 ` Peter Zijlstra [this message]
2018-05-02 18:27 ` Daniel Colascione
2018-05-02 20:22 ` Peter Zijlstra
2018-05-02 20:37 ` Daniel Colascione
2018-05-03 1:15 ` Steven Rostedt
2018-05-03 8:49 ` Peter Zijlstra
2018-05-06 10:03 ` Thomas Gleixner
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