From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: David Laight <David.Laight@ACULAB.COM>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"netfilter-devel@vger.kernel.org"
<netfilter-devel@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"oleg@redhat.com" <oleg@redhat.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"mingo@redhat.com" <mingo@redhat.com>,
"dave@stgolabs.net" <dave@stgolabs.net>,
"manfred@colorfullife.com" <manfred@colorfullife.com>,
"tj@kernel.org" <tj@kernel.org>, "arnd@arndb.de" <arnd@arndb.de>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"will.deacon@arm.com" <will.deacon@arm.com>,
"stern@rowland.harvard.edu" <stern@rowland.harvard.edu>,
"parri.andrea@gmail.com" <parri.andrea@gmail.com>,
"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>
Subject: Re: [PATCH v2 0/9] Remove spin_unlock_wait()
Date: Thu, 6 Jul 2017 18:41:34 +0200 [thread overview]
Message-ID: <20170706164134.6a54adwcdvjx6ouc@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20170706162412.GE2393@linux.vnet.ibm.com>
On Thu, Jul 06, 2017 at 09:24:12AM -0700, Paul E. McKenney wrote:
> On Thu, Jul 06, 2017 at 06:10:47PM +0200, Peter Zijlstra wrote:
> > On Thu, Jul 06, 2017 at 08:21:10AM -0700, Paul E. McKenney wrote:
> > > And yes, there are architecture-specific optimizations for an
> > > empty spin_lock()/spin_unlock() critical section, and the current
> > > arch_spin_unlock_wait() implementations show some of these optimizations.
> > > But I expect that performance benefits would need to be demonstrated at
> > > the system level.
> >
> > I do in fact contended there are any optimizations for the exact
> > lock+unlock semantics.
>
> You lost me on this one.
For the exact semantics you'd have to fully participate in the fairness
protocol. You have to in fact acquire the lock in order to have the
other contending CPUs wait (otherwise my earlier case 3 will fail).
At that point I'm not sure there is much actual code you can leave out.
What actual optimization is there left at that point?
next prev parent reply other threads:[~2017-07-06 16:42 UTC|newest]
Thread overview: 122+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-29 23:59 [PATCH RFC 0/26] Remove spin_unlock_wait() Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 01/26] netfilter: Replace spin_unlock_wait() with lock/unlock pair Paul E. McKenney
[not found] ` <a6642feb-2f3a-980f-5ed6-2deb79563e6b@colorfullife.com>
2017-07-02 2:00 ` Paul E. McKenney
2017-07-03 14:39 ` Alan Stern
2017-07-03 17:14 ` Paul E. McKenney
2017-07-03 19:01 ` Manfred Spraul
2017-07-03 19:57 ` Alan Stern
2017-07-06 18:43 ` Manfred Spraul
2017-07-03 20:04 ` Alan Stern
2017-07-03 20:53 ` Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 02/26] task_work: " Paul E. McKenney
2017-06-30 11:04 ` Oleg Nesterov
2017-06-30 12:50 ` Paul E. McKenney
2017-06-30 15:20 ` Oleg Nesterov
2017-06-30 16:16 ` Paul E. McKenney
2017-06-30 17:21 ` Paul E. McKenney
2017-06-30 19:21 ` Oleg Nesterov
2017-06-30 19:50 ` Alan Stern
2017-06-30 20:04 ` Paul E. McKenney
2017-06-30 20:02 ` Paul E. McKenney
2017-06-30 20:19 ` Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 03/26] sched: " Paul E. McKenney
2017-06-30 10:31 ` Arnd Bergmann
2017-06-30 12:35 ` Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 04/26] completion: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 05/26] exit: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 07/26] drivers/ata: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 08/26] locking: Remove spin_unlock_wait() generic definitions Paul E. McKenney
2017-06-30 9:19 ` Will Deacon
2017-06-30 12:38 ` Paul E. McKenney
2017-06-30 13:13 ` Will Deacon
2017-06-30 22:18 ` Paul E. McKenney
2017-07-03 13:15 ` Will Deacon
2017-07-03 16:18 ` Paul E. McKenney
2017-07-03 16:40 ` Linus Torvalds
2017-07-03 17:13 ` Will Deacon
2017-07-03 22:30 ` Paul E. McKenney
2017-07-03 22:49 ` Linus Torvalds
2017-07-04 0:39 ` Paul E. McKenney
2017-07-04 0:54 ` Paul E. McKenney
2017-07-03 21:10 ` Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 09/26] alpha: Remove spin_unlock_wait() arch-specific definitions Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 10/26] arc: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 11/26] arm: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 12/26] arm64: " Paul E. McKenney
2017-06-30 9:20 ` Will Deacon
2017-06-30 17:29 ` Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 13/26] blackfin: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 14/26] hexagon: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 15/26] ia64: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 16/26] m32r: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 18/26] mips: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 19/26] mn10300: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 20/26] parisc: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 21/26] powerpc: " Paul E. McKenney
2017-07-02 3:58 ` Boqun Feng
2017-07-05 23:57 ` Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 22/26] s390: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 23/26] sh: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 24/26] sparc: " Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 25/26] tile: " Paul E. McKenney
2017-06-30 0:06 ` Linus Torvalds
2017-06-30 0:09 ` Paul E. McKenney
2017-06-30 0:14 ` Paul E. McKenney
2017-06-30 0:10 ` Linus Torvalds
2017-06-30 0:24 ` Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 26/26] xtensa: " Paul E. McKenney
[not found] ` <1498780894-8253-6-git-send-email-paulmck@linux.vnet.ibm.com>
2017-07-01 19:23 ` [PATCH RFC 06/26] ipc: Replace spin_unlock_wait() with lock/unlock pair Manfred Spraul
2017-07-02 3:16 ` Paul E. McKenney
2017-07-05 23:29 ` [PATCH v2 0/9] Remove spin_unlock_wait() Paul E. McKenney
2017-07-05 23:31 ` [PATCH v2 1/9] net/netfilter/nf_conntrack_core: Fix net_conntrack_lock() Paul E. McKenney
2017-07-06 18:45 ` Manfred Spraul
2017-07-06 20:26 ` Paul E. McKenney
2017-07-05 23:31 ` [PATCH v2 2/9] task_work: Replace spin_unlock_wait() with lock/unlock pair Paul E. McKenney
2017-07-05 23:31 ` [PATCH v2 3/9] sched: " Paul E. McKenney
2017-07-05 23:31 ` [PATCH v2 4/9] completion: " Paul E. McKenney
2017-07-05 23:31 ` [PATCH v2 5/9] exit: " Paul E. McKenney
2017-07-05 23:31 ` [PATCH v2 6/9] ipc: " Paul E. McKenney
2017-07-05 23:31 ` [PATCH v2 7/9] drivers/ata: " Paul E. McKenney
2017-07-05 23:31 ` [PATCH v2 8/9] locking: Remove spin_unlock_wait() generic definitions Paul E. McKenney
2017-07-05 23:31 ` [PATCH v2 9/9] arch: Remove spin_unlock_wait() arch-specific definitions Paul E. McKenney
2017-07-06 14:12 ` [PATCH v2 0/9] Remove spin_unlock_wait() David Laight
2017-07-06 15:21 ` Paul E. McKenney
2017-07-06 16:10 ` Peter Zijlstra
2017-07-06 16:24 ` Paul E. McKenney
2017-07-06 16:41 ` Peter Zijlstra [this message]
2017-07-06 17:03 ` Paul E. McKenney
2017-07-06 16:49 ` Alan Stern
2017-07-06 16:54 ` Peter Zijlstra
2017-07-06 19:37 ` Alan Stern
2017-07-06 16:05 ` Peter Zijlstra
2017-07-06 16:20 ` Paul E. McKenney
2017-07-06 16:50 ` Peter Zijlstra
2017-07-06 17:08 ` Will Deacon
2017-07-06 17:29 ` Paul E. McKenney
2017-07-06 17:18 ` Paul E. McKenney
2017-07-07 8:31 ` Ingo Molnar
2017-07-07 8:44 ` Peter Zijlstra
2017-07-07 10:33 ` Ingo Molnar
2017-07-07 11:23 ` Peter Zijlstra
2017-07-07 14:41 ` Paul E. McKenney
2017-07-08 8:43 ` Ingo Molnar
2017-07-08 11:41 ` Paul E. McKenney
2017-07-07 17:47 ` Manfred Spraul
2017-07-08 8:35 ` Ingo Molnar
2017-07-08 11:39 ` Paul E. McKenney
2017-07-08 12:30 ` Ingo Molnar
2017-07-08 14:45 ` Paul E. McKenney
2017-07-08 16:21 ` Alan Stern
2017-07-10 17:22 ` Manfred Spraul
2017-07-07 8:06 ` Ingo Molnar
2017-07-07 9:32 ` Ingo Molnar
2017-07-07 19:27 ` [PATCH v3 " Paul E. McKenney
2017-07-07 19:28 ` [PATCH v3 1/9] net/netfilter/nf_conntrack_core: Fix net_conntrack_lock() Paul E. McKenney
2017-07-07 19:28 ` [PATCH v3 2/9] task_work: Replace spin_unlock_wait() with lock/unlock pair Paul E. McKenney
2017-07-07 19:28 ` [PATCH v3 3/9] sched: " Paul E. McKenney
2017-07-07 19:28 ` [PATCH v3 4/9] completion: " Paul E. McKenney
2017-07-07 19:28 ` [PATCH v3 5/9] exit: " Paul E. McKenney
2017-07-07 19:28 ` [PATCH v3 6/9] ipc: " Paul E. McKenney
2017-07-07 19:28 ` [PATCH v3 7/9] drivers/ata: " Paul E. McKenney
2017-07-07 19:28 ` [PATCH v3 8/9] locking: Remove spin_unlock_wait() generic definitions Paul E. McKenney
2017-07-07 19:28 ` [PATCH v3 9/9] arch: Remove spin_unlock_wait() arch-specific definitions Paul E. McKenney
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