From: tip-bot for Will Deacon <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: torvalds@linux-foundation.org, peterz@infradead.org,
longman@redhat.com, linux-kernel@vger.kernel.org,
will.deacon@arm.com, mingo@kernel.org, tglx@linutronix.de,
hpa@zytor.com
Subject: [tip:locking/core] locking/qspinlock/x86: Increase _Q_PENDING_LOOPS upper bound
Date: Fri, 27 Apr 2018 02:38:35 -0700 [thread overview]
Message-ID: <tip-b247be3fe89b6aba928bf80f4453d1c4ba8d2063@git.kernel.org> (raw)
In-Reply-To: <1524738868-31318-5-git-send-email-will.deacon@arm.com>
Commit-ID: b247be3fe89b6aba928bf80f4453d1c4ba8d2063
Gitweb: https://git.kernel.org/tip/b247be3fe89b6aba928bf80f4453d1c4ba8d2063
Author: Will Deacon <will.deacon@arm.com>
AuthorDate: Thu, 26 Apr 2018 11:34:18 +0100
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 27 Apr 2018 09:48:47 +0200
locking/qspinlock/x86: Increase _Q_PENDING_LOOPS upper bound
On x86, atomic_cond_read_relaxed will busy-wait with a cpu_relax() loop,
so it is desirable to increase the number of times we spin on the qspinlock
lockword when it is found to be transitioning from pending to locked.
According to Waiman Long:
| Ideally, the spinning times should be at least a few times the typical
| cacheline load time from memory which I think can be down to 100ns or
| so for each cacheline load with the newest systems or up to several
| hundreds ns for older systems.
which in his benchmarking corresponded to 512 iterations.
Suggested-by: Waiman Long <longman@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: boqun.feng@gmail.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/1524738868-31318-5-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/qspinlock.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h
index 90b0b0ed8161..da1370ad206d 100644
--- a/arch/x86/include/asm/qspinlock.h
+++ b/arch/x86/include/asm/qspinlock.h
@@ -7,6 +7,8 @@
#include <asm-generic/qspinlock_types.h>
#include <asm/paravirt.h>
+#define _Q_PENDING_LOOPS (1 << 9)
+
#define queued_spin_unlock queued_spin_unlock
/**
* queued_spin_unlock - release a queued spinlock
next prev parent reply other threads:[~2018-04-27 9:38 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-26 10:34 [PATCH v3 00/14] kernel/locking: qspinlock improvements Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-26 10:34 ` [PATCH v3 01/14] barriers: Introduce smp_cond_load_relaxed and atomic_cond_read_relaxed Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-27 9:36 ` [tip:locking/core] locking/barriers: Introduce smp_cond_load_relaxed() and atomic_cond_read_relaxed() tip-bot for Will Deacon
2018-04-26 10:34 ` [PATCH v3 02/14] locking/qspinlock: Merge struct __qspinlock into struct qspinlock Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-27 9:37 ` [tip:locking/core] locking/qspinlock: Merge 'struct __qspinlock' into 'struct qspinlock' tip-bot for Will Deacon
2018-04-26 10:34 ` [PATCH v3 03/14] locking/qspinlock: Bound spinning on pending->locked transition in slowpath Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-27 9:37 ` [tip:locking/core] " tip-bot for Will Deacon
2018-04-26 10:34 ` [PATCH v3 04/14] locking/qspinlock/x86: Increase _Q_PENDING_LOOPS upper bound Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-27 9:38 ` tip-bot for Will Deacon [this message]
2018-04-26 10:34 ` [PATCH v3 05/14] locking/qspinlock: Remove unbounded cmpxchg loop from locking slowpath Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-26 15:53 ` Peter Zijlstra
2018-04-26 15:53 ` Peter Zijlstra
2018-04-26 16:55 ` Will Deacon
2018-04-26 16:55 ` Will Deacon
2018-04-28 12:45 ` Peter Zijlstra
2018-04-28 12:45 ` Peter Zijlstra
2018-04-30 8:53 ` Will Deacon
2018-04-30 8:53 ` Will Deacon
2018-04-26 20:16 ` Waiman Long
2018-04-26 20:16 ` Waiman Long
2018-04-27 10:16 ` Will Deacon
2018-04-27 10:16 ` Will Deacon
2018-04-27 11:01 ` [tip:locking/core] locking/qspinlock: Remove duplicate clear_pending() function from PV code tip-bot for Will Deacon
2018-04-27 13:09 ` [PATCH v3 05/14] locking/qspinlock: Remove unbounded cmpxchg loop from locking slowpath Waiman Long
2018-04-27 13:09 ` Waiman Long
2018-04-27 9:39 ` [tip:locking/core] locking/qspinlock: Remove unbounded cmpxchg() " tip-bot for Will Deacon
2018-04-26 10:34 ` [PATCH v3 06/14] locking/qspinlock: Kill cmpxchg loop when claiming lock from head of queue Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-27 9:39 ` [tip:locking/core] locking/qspinlock: Kill cmpxchg() " tip-bot for Will Deacon
2018-04-26 10:34 ` [PATCH v3 07/14] locking/qspinlock: Use atomic_cond_read_acquire Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-27 9:40 ` [tip:locking/core] locking/qspinlock: Use atomic_cond_read_acquire() tip-bot for Will Deacon
2018-04-26 10:34 ` [PATCH v3 08/14] locking/mcs: Use smp_cond_load_acquire() in mcs spin loop Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-27 9:40 ` [tip:locking/core] locking/mcs: Use smp_cond_load_acquire() in MCS " tip-bot for Jason Low
2018-04-26 10:34 ` [PATCH v3 09/14] locking/qspinlock: Use smp_cond_load_relaxed to wait for next node Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-27 9:41 ` [tip:locking/core] locking/qspinlock: Use smp_cond_load_relaxed() " tip-bot for Will Deacon
2018-04-26 10:34 ` [PATCH v3 10/14] locking/qspinlock: Make queued_spin_unlock use smp_store_release Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-27 9:42 ` [tip:locking/core] locking/qspinlock: Use smp_store_release() in queued_spin_unlock() tip-bot for Will Deacon
2018-04-26 10:34 ` [PATCH v3 11/14] locking/qspinlock: Elide back-to-back RELEASE operations with smp_wmb() Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-27 9:42 ` [tip:locking/core] " tip-bot for Will Deacon
2018-04-26 10:34 ` [PATCH v3 12/14] locking/qspinlock: Use try_cmpxchg instead of cmpxchg when locking Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-27 9:43 ` [tip:locking/core] locking/qspinlock: Use try_cmpxchg() instead of cmpxchg() " tip-bot for Will Deacon
2018-04-26 10:34 ` [PATCH v3 13/14] locking/qspinlock: Add stat tracking for pending vs slowpath Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-27 9:43 ` [tip:locking/core] locking/qspinlock: Add stat tracking for pending vs. slowpath tip-bot for Waiman Long
2018-04-26 10:34 ` [PATCH v3 14/14] MAINTAINERS: Add myself as a co-maintainer for LOCKING PRIMITIVES Will Deacon
2018-04-26 10:34 ` Will Deacon
2018-04-26 15:55 ` Peter Zijlstra
2018-04-26 15:55 ` Peter Zijlstra
2018-04-27 9:44 ` [tip:locking/core] MAINTAINERS: Add myself as a co-maintainer for the locking subsystem tip-bot for Will Deacon
2018-04-26 15:54 ` [PATCH v3 00/14] kernel/locking: qspinlock improvements Peter Zijlstra
2018-04-26 15:54 ` Peter Zijlstra
2018-04-27 9:33 ` Ingo Molnar
2018-04-27 9:33 ` Ingo Molnar
2018-04-26 20:18 ` Waiman Long
2018-04-26 20:18 ` Waiman Long
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