From: Eric Dumazet <eric.dumazet@gmail.com>
To: Rik van Riel <riel@redhat.com>
Cc: linux-kernel@vger.kernel.org, aquini@redhat.com,
walken@google.com, lwoodman@redhat.com, jeremy@goop.org,
Jan Beulich <JBeulich@novell.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [RFC PATCH 3/3 -v2] x86,smp: auto tune spinlock backoff delay factor
Date: Fri, 21 Dec 2012 16:48:52 -0800 [thread overview]
Message-ID: <1356137332.21834.8155.camel@edumazet-glaptop> (raw)
In-Reply-To: <20121221185613.1f4c9523@annuminas.surriel.com>
On Fri, 2012-12-21 at 18:56 -0500, Rik van Riel wrote:
> Argh, the first one had a typo in it that did not influence
> performance with fewer threads running, but that made things
> worse with more than a dozen threads...
>
> Please let me know if you can break these patches.
> ---8<---
> Subject: x86,smp: auto tune spinlock backoff delay factor
> +#define MIN_SPINLOCK_DELAY 1
> +#define MAX_SPINLOCK_DELAY 1000
> +DEFINE_PER_CPU(int, spinlock_delay) = { MIN_SPINLOCK_DELAY };
Using a single spinlock_delay per cpu assumes there is a single
contended spinlock on the machine, or that contended
spinlocks protect the same critical section.
Given that we probably know where the contended spinlocks are, couldnt
we use a real scalable implementation for them ?
A known contended one is the Qdisc lock in network layer. We added a
second lock (busylock) to lower a bit the pressure on a separate cache
line, but a scalable lock would be much better...
I guess there are patent issues...
next prev parent reply other threads:[~2012-12-22 0:48 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-21 23:49 [RFC PATCH 0/3] x86,smp: make ticket spinlock proportional backoff w/ auto tuning Rik van Riel
2012-12-21 23:50 ` [RFC PATCH 1/3] x86,smp: move waiting on contended lock out of line Rik van Riel
2012-12-22 3:05 ` Steven Rostedt
2012-12-22 4:40 ` Michel Lespinasse
2012-12-22 4:48 ` Rik van Riel
2012-12-23 22:52 ` Rafael Aquini
2012-12-21 23:51 ` [RFC PATCH 2/3] x86,smp: proportional backoff for ticket spinlocks Rik van Riel
2012-12-22 3:07 ` Steven Rostedt
2012-12-22 3:14 ` Steven Rostedt
2012-12-22 3:47 ` Rik van Riel
2012-12-22 4:44 ` Michel Lespinasse
2012-12-23 22:55 ` Rafael Aquini
2012-12-21 23:51 ` [RFC PATCH 3/3] x86,smp: auto tune spinlock backoff delay factor Rik van Riel
2012-12-21 23:56 ` [RFC PATCH 3/3 -v2] " Rik van Riel
2012-12-22 0:18 ` Eric Dumazet
2012-12-22 2:43 ` Rik van Riel
2012-12-22 0:48 ` Eric Dumazet [this message]
2012-12-22 2:57 ` Rik van Riel
2012-12-22 3:29 ` Eric Dumazet
2012-12-22 3:44 ` Rik van Riel
2012-12-22 3:33 ` Steven Rostedt
2012-12-22 3:50 ` Rik van Riel
2012-12-26 19:10 ` Eric Dumazet
2012-12-26 19:27 ` Eric Dumazet
2012-12-26 19:51 ` Rik van Riel
2012-12-27 6:07 ` Michel Lespinasse
2012-12-27 14:27 ` Eric Dumazet
2012-12-27 14:35 ` Rik van Riel
2012-12-27 18:41 ` Jan Beulich
2012-12-27 19:09 ` Rik van Riel
2013-01-03 9:05 ` Jan Beulich
2013-01-03 13:24 ` Steven Rostedt
2013-01-03 13:35 ` Eric Dumazet
2013-01-03 15:32 ` Steven Rostedt
2013-01-03 16:10 ` Eric Dumazet
2013-01-03 16:45 ` Steven Rostedt
2013-01-03 17:54 ` Eric Dumazet
2012-12-27 18:49 ` Eric Dumazet
2012-12-27 19:31 ` Rik van Riel
2012-12-29 0:42 ` Eric Dumazet
2012-12-29 10:27 ` Michel Lespinasse
2013-01-03 18:17 ` Eric Dumazet
2012-12-22 0:47 ` [RFC PATCH 3/3] " David Daney
2012-12-22 2:51 ` Rik van Riel
2012-12-22 3:49 ` Steven Rostedt
2012-12-22 3:58 ` Rik van Riel
2012-12-23 23:08 ` Rafael Aquini
2012-12-22 5:42 ` Michel Lespinasse
2012-12-22 14:32 ` Rik van Riel
2013-01-02 0:06 ` ticket spinlock proportional backoff experiments Michel Lespinasse
2013-01-02 0:09 ` [PATCH 1/2] x86,smp: simplify __ticket_spin_lock Michel Lespinasse
2013-01-02 15:31 ` Rik van Riel
2013-01-02 0:10 ` [PATCH 2/2] x86,smp: proportional backoff for ticket spinlocks Michel Lespinasse
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