From: Christoph Lameter <cl@linux.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Peter Zijlstra <peterz@infradead.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Andrew Morton <akpm@linux-foundation.org>,
Russell King <linux@arm.linux.org.uk>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
linux-api <linux-api@vger.kernel.org>,
Paul Turner <pjt@google.com>, Andrew Hunter <ahh@google.com>,
Andi Kleen <andi@firstfloor.org>,
Dave Watson <davejwatson@fb.com>, Ben Maurer <bmaurer@fb.com>,
rostedt <rostedt@goodmis.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Josh Triplett <josh@joshtriplett.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Michael Kerrisk <mtk.manpages@gmail.com>,
Boqun Feng <boqun.feng@gmail.com>
Subject: Re: [RFC PATCH v7 1/7] Restartable sequences system call
Date: Wed, 3 Aug 2016 13:31:30 -0500 (CDT) [thread overview]
Message-ID: <alpine.DEB.2.20.1608031330000.14875@east.gentwo.org> (raw)
In-Reply-To: <CALCETrWw0M9YLWTR7_ruxY8cW9_5XRONdw1QN+_pBp0Y63L8pA@mail.gmail.com>
On Wed, 3 Aug 2016, Andy Lutomirski wrote:
> > Well, a CMPXCHG without LOCK prefix isn't all that expensive on x86.
> >
> > It is however on PPC and possibly other architectures, so in name of
> > simplicity supporting only the one variant makes sense.
> >
>
> I wouldn't want to depend on CMPXCHG. But imagine we had primitives
> that were narrower than the full abort-on-preemption primitive.
> Specifically, suppose we had abort if (actual cpu != expected_cpu ||
> *aptr != aval). We could do things like:
>
The latency issues that are addressed by restartable sequences require
minimim instruction overhead. Lockless CMPXCHG is very important in that
area and I would not simply remove it from consideration.
next prev parent reply other threads:[~2016-08-03 18:31 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-21 21:14 [RFC PATCH v7 0/7] Restartable sequences system call Mathieu Desnoyers
2016-07-21 21:14 ` [RFC PATCH v7 1/7] " Mathieu Desnoyers
2016-07-25 23:02 ` Andy Lutomirski
2016-07-26 3:02 ` Mathieu Desnoyers
2016-08-03 12:27 ` Peter Zijlstra
2016-08-03 16:37 ` Andy Lutomirski
2016-08-03 18:31 ` Christoph Lameter [this message]
2016-08-04 5:01 ` Andy Lutomirski
2016-08-04 4:27 ` Boqun Feng
2016-08-04 5:03 ` Andy Lutomirski
2016-08-09 16:13 ` Boqun Feng
2016-08-10 8:01 ` Andy Lutomirski
2016-08-10 17:40 ` Mathieu Desnoyers
2016-08-10 17:33 ` Mathieu Desnoyers
2016-08-11 4:54 ` Boqun Feng
2016-08-10 8:13 ` Andy Lutomirski
2016-08-03 18:29 ` Christoph Lameter
2016-08-10 16:47 ` Mathieu Desnoyers
2016-08-10 16:59 ` Christoph Lameter
2016-07-27 15:03 ` Boqun Feng
2016-07-27 15:05 ` [RFC 1/4] rseq/param_test: Convert test_data_entry::count to intptr_t Boqun Feng
2016-07-27 15:05 ` [RFC 2/4] Restartable sequences: powerpc architecture support Boqun Feng
2016-07-28 3:13 ` Mathieu Desnoyers
2016-07-27 15:05 ` [RFC 3/4] Restartable sequences: Wire up powerpc system call Boqun Feng
2016-07-28 3:13 ` Mathieu Desnoyers
2016-07-27 15:05 ` [RFC 4/4] Restartable sequences: Add self-tests for PPC Boqun Feng
2016-07-28 2:59 ` Mathieu Desnoyers
2016-07-28 4:43 ` Boqun Feng
2016-07-28 7:37 ` [RFC v2] " Boqun Feng
2016-07-28 14:04 ` Mathieu Desnoyers
2016-07-28 13:42 ` [RFC 4/4] " Mathieu Desnoyers
2016-07-28 3:07 ` [RFC 1/4] rseq/param_test: Convert test_data_entry::count to intptr_t Mathieu Desnoyers
2016-07-28 3:10 ` [RFC PATCH v7 1/7] Restartable sequences system call Mathieu Desnoyers
2016-08-03 13:19 ` Peter Zijlstra
2016-08-03 14:53 ` Paul E. McKenney
2016-08-03 15:45 ` Boqun Feng
2016-08-07 15:36 ` Mathieu Desnoyers
2016-08-07 23:35 ` Boqun Feng
2016-08-09 13:22 ` Mathieu Desnoyers
2016-08-09 20:06 ` Mathieu Desnoyers
2016-08-09 21:33 ` Peter Zijlstra
2016-08-09 22:41 ` Mathieu Desnoyers
2016-08-10 7:50 ` Peter Zijlstra
2016-08-10 13:26 ` Mathieu Desnoyers
2016-08-10 13:33 ` Peter Zijlstra
2016-08-10 14:04 ` Mathieu Desnoyers
2016-08-10 8:10 ` Andy Lutomirski
2016-08-10 19:04 ` Mathieu Desnoyers
2016-08-10 19:16 ` Andy Lutomirski
2016-08-10 20:06 ` Mathieu Desnoyers
2016-08-10 20:09 ` Andy Lutomirski
2016-08-10 21:01 ` Mathieu Desnoyers
2016-08-11 7:23 ` Andy Lutomirski
2016-08-10 8:43 ` Peter Zijlstra
2016-08-10 13:57 ` Mathieu Desnoyers
2016-08-10 14:28 ` Peter Zijlstra
2016-08-10 14:44 ` Mathieu Desnoyers
2016-08-10 13:29 ` Peter Zijlstra
2016-07-21 21:14 ` [RFC PATCH v7 2/7] tracing: instrument restartable sequences Mathieu Desnoyers
2016-07-21 21:14 ` [RFC PATCH v7 3/7] Restartable sequences: ARM 32 architecture support Mathieu Desnoyers
2016-07-21 21:14 ` [RFC PATCH v7 4/7] Restartable sequences: wire up ARM 32 system call Mathieu Desnoyers
2016-07-21 21:14 ` [RFC PATCH v7 5/7] Restartable sequences: x86 32/64 architecture support Mathieu Desnoyers
2016-07-21 21:14 ` [RFC PATCH v7 6/7] Restartable sequences: wire up x86 32/64 system call Mathieu Desnoyers
2016-07-21 21:14 ` [RFC PATCH v7 7/7] Restartable sequences: self-tests Mathieu Desnoyers
[not found] ` <CO1PR15MB09822FC140F84DCEEF2004CDDD0B0@CO1PR15MB0982.namprd15.prod.outlook.com>
2016-07-24 3:09 ` Mathieu Desnoyers
2016-07-24 18:01 ` Dave Watson
2016-07-25 16:43 ` Mathieu Desnoyers
2016-08-11 23:26 ` Mathieu Desnoyers
2016-08-12 1:28 ` Boqun Feng
2016-08-12 3:10 ` Mathieu Desnoyers
2016-08-12 3:13 ` Mathieu Desnoyers
2016-08-12 5:30 ` Boqun Feng
2016-08-12 16:35 ` Boqun Feng
2016-08-12 18:11 ` Mathieu Desnoyers
2016-08-13 1:28 ` Boqun Feng
2016-08-14 15:02 ` Mathieu Desnoyers
2016-08-15 0:56 ` Boqun Feng
2016-08-15 18:06 ` Mathieu Desnoyers
2016-08-12 19:36 ` Mathieu Desnoyers
2016-08-12 20:05 ` Dave Watson
2016-08-14 17:09 ` Mathieu Desnoyers
2016-07-25 18:12 ` Mathieu Desnoyers
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