From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>, Will Deacon <will.deacon@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, x86@kernel.org,
Davidlohr Bueso <dave@stgolabs.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
huang ying <huang.ying.caritas@gmail.com>
Subject: Re: [PATCH v4 07/16] locking/rwsem: Implement lock handoff to prevent lock starvation
Date: Tue, 16 Apr 2019 16:12:05 +0200 [thread overview]
Message-ID: <20190416141205.GK12232@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190413172259.2740-8-longman@redhat.com>
On Sat, Apr 13, 2019 at 01:22:50PM -0400, Waiman Long wrote:
> +/*
> + * The typical HZ value is either 250 or 1000. So set the minimum waiting
> + * time to 4ms in the wait queue before initiating the handoff protocol.
> + */
> +#define RWSEM_WAIT_TIMEOUT (HZ/250)
That seems equally unfortunate. For HZ=100 that results in 0ms, and for
HZ=300 that results in 3 1/3-rd ms.
(and this is not considering Alpha,ARM and MIPS, who all have various
other 'creative' HZ values)
In general aiming for sub 10ms timing using jiffies seems 'optimistic'.
next prev parent reply other threads:[~2019-04-16 14:12 UTC|newest]
Thread overview: 112+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-13 17:22 [PATCH v4 00/16] locking/rwsem: Rwsem rearchitecture part 2 Waiman Long
2019-04-13 17:22 ` [PATCH v4 01/16] locking/rwsem: Prevent unneeded warning during locking selftest Waiman Long
2019-04-18 8:04 ` [tip:locking/core] " tip-bot for Waiman Long
2019-04-13 17:22 ` [PATCH v4 02/16] locking/rwsem: Make owner available even if !CONFIG_RWSEM_SPIN_ON_OWNER Waiman Long
2019-04-13 17:22 ` [PATCH v4 03/16] locking/rwsem: Remove rwsem_wake() wakeup optimization Waiman Long
2019-04-13 17:22 ` [PATCH v4 04/16] locking/rwsem: Implement a new locking scheme Waiman Long
2019-04-16 13:22 ` Peter Zijlstra
2019-04-16 13:32 ` Waiman Long
2019-04-16 14:18 ` Peter Zijlstra
2019-04-16 14:42 ` Peter Zijlstra
2019-04-13 17:22 ` [PATCH v4 05/16] locking/rwsem: Merge rwsem.h and rwsem-xadd.c into rwsem.c Waiman Long
2019-04-13 17:22 ` [PATCH v4 06/16] locking/rwsem: Code cleanup after files merging Waiman Long
2019-04-16 16:01 ` Peter Zijlstra
2019-04-16 16:17 ` Peter Zijlstra
2019-04-16 19:45 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 07/16] locking/rwsem: Implement lock handoff to prevent lock starvation Waiman Long
2019-04-16 14:12 ` Peter Zijlstra [this message]
2019-04-16 20:26 ` Waiman Long
2019-04-16 21:07 ` Waiman Long
2019-04-17 7:13 ` Peter Zijlstra
2019-04-17 16:22 ` Waiman Long
2019-04-16 15:49 ` Peter Zijlstra
2019-04-16 16:15 ` Peter Zijlstra
2019-04-16 18:41 ` Waiman Long
2019-04-16 18:16 ` Waiman Long
2019-04-16 18:32 ` Peter Zijlstra
2019-04-17 7:35 ` Peter Zijlstra
2019-04-17 16:35 ` Waiman Long
2019-04-17 8:05 ` Peter Zijlstra
2019-04-17 16:39 ` Waiman Long
2019-04-18 8:22 ` Peter Zijlstra
2019-04-17 8:17 ` Peter Zijlstra
2019-04-13 17:22 ` [PATCH v4 08/16] locking/rwsem: Make rwsem_spin_on_owner() return owner state Waiman Long
2019-04-17 9:00 ` Peter Zijlstra
2019-04-17 16:42 ` Waiman Long
2019-04-17 10:19 ` Peter Zijlstra
2019-04-17 16:53 ` Waiman Long
2019-04-17 12:41 ` Peter Zijlstra
2019-04-17 12:47 ` Peter Zijlstra
2019-04-17 18:29 ` Waiman Long
2019-04-18 8:39 ` Peter Zijlstra
2019-04-17 13:00 ` Peter Zijlstra
2019-04-17 18:50 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 09/16] locking/rwsem: Ensure an RT task will not spin on reader Waiman Long
2019-04-17 13:18 ` Peter Zijlstra
2019-04-17 18:47 ` Waiman Long
2019-04-18 8:52 ` Peter Zijlstra
2019-04-18 13:27 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 10/16] locking/rwsem: Wake up almost all readers in wait queue Waiman Long
2019-04-16 16:50 ` Davidlohr Bueso
2019-04-16 17:37 ` Waiman Long
2019-04-17 13:39 ` Peter Zijlstra
2019-04-17 17:16 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 11/16] locking/rwsem: Enable readers spinning on writer Waiman Long
2019-04-17 13:56 ` Peter Zijlstra
2019-04-17 17:34 ` Waiman Long
2019-04-18 8:57 ` Peter Zijlstra
2019-04-18 14:35 ` Waiman Long
2019-04-17 13:58 ` Peter Zijlstra
2019-04-17 17:45 ` Waiman Long
2019-04-18 9:00 ` Peter Zijlstra
2019-04-18 13:40 ` Waiman Long
2019-04-17 14:05 ` Peter Zijlstra
2019-04-17 17:51 ` Waiman Long
2019-04-18 9:11 ` Peter Zijlstra
2019-04-18 14:37 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 12/16] locking/rwsem: Enable time-based spinning on reader-owned rwsem Waiman Long
2019-04-18 13:06 ` Peter Zijlstra
2019-04-18 15:15 ` Waiman Long
2019-04-19 7:56 ` Peter Zijlstra
2019-04-19 14:33 ` Waiman Long
2019-04-19 15:36 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 13/16] locking/rwsem: Add more rwsem owner access helpers Waiman Long
2019-04-13 17:22 ` [PATCH v4 14/16] locking/rwsem: Guard against making count negative Waiman Long
2019-04-18 13:51 ` Peter Zijlstra
2019-04-18 14:08 ` Waiman Long
2019-04-18 14:30 ` Peter Zijlstra
2019-04-18 14:40 ` Peter Zijlstra
2019-04-18 14:54 ` Waiman Long
2019-04-19 10:26 ` Peter Zijlstra
2019-04-19 12:02 ` Peter Zijlstra
2019-04-19 13:03 ` Peter Zijlstra
2019-04-19 13:15 ` Peter Zijlstra
2019-04-19 19:39 ` Waiman Long
2019-04-21 21:07 ` Waiman Long
2019-04-23 14:17 ` Peter Zijlstra
2019-04-23 14:31 ` Waiman Long
2019-04-23 16:27 ` Linus Torvalds
2019-04-23 19:12 ` Waiman Long
2019-04-23 19:34 ` Peter Zijlstra
2019-04-23 19:41 ` Waiman Long
2019-04-23 19:55 ` [PATCH] bpf: Fix preempt_enable_no_resched() abuse Peter Zijlstra
2019-04-23 20:03 ` [PATCH] trace: " Peter Zijlstra
2019-04-23 23:58 ` Steven Rostedt
2019-04-29 6:39 ` [tip:sched/core] " tip-bot for Peter Zijlstra
2019-04-29 13:31 ` Steven Rostedt
2019-04-29 14:08 ` Ingo Molnar
2019-04-23 20:27 ` [PATCH] bpf: " Linus Torvalds
2019-04-23 20:35 ` Peter Zijlstra
2019-04-23 20:45 ` Linus Torvalds
2019-04-24 13:19 ` Peter Zijlstra
2019-04-25 21:23 ` Alexei Starovoitov
2019-04-26 7:14 ` Peter Zijlstra
2019-04-24 7:09 ` [PATCH v4 14/16] locking/rwsem: Guard against making count negative Peter Zijlstra
2019-04-24 16:49 ` Waiman Long
2019-04-24 17:01 ` Peter Zijlstra
2019-04-24 17:10 ` Waiman Long
2019-04-24 17:56 ` Linus Torvalds
2019-04-13 17:22 ` [PATCH v4 15/16] locking/rwsem: Merge owner into count on x86-64 Waiman Long
2019-04-18 14:28 ` Peter Zijlstra
2019-04-18 14:40 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 16/16] locking/rwsem: Remove redundant computation of writer lock word Waiman Long
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