linux-kernel - Re: [RFC PATCH 2/3] x86,smp: proportional backoff for ticket spinlocks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20121223225507.GB4186@x61.redhat.com>
Date:	Sun, 23 Dec 2012 20:55:08 -0200
From:	Rafael Aquini <aquini@...hat.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	linux-kernel@...r.kernel.org, walken@...gle.com,
	lwoodman@...hat.com, jeremy@...p.org,
	Jan Beulich <JBeulich@...ell.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH 2/3] x86,smp: proportional backoff for ticket
 spinlocks

On Fri, Dec 21, 2012 at 06:51:15PM -0500, Rik van Riel wrote:
> Subject: x86,smp: proportional backoff for ticket spinlocks
> 
> Simple fixed value proportional backoff for ticket spinlocks.
> By pounding on the cacheline with the spin lock less often,
> bus traffic is reduced. In cases of a data structure with
> embedded spinlock, the lock holder has a better chance of
> making progress.
> 
> Signed-off-by: Rik van Riel <riel@...hat.com>
> ---

Reviewed-by: Rafael Aquini <aquini@...hat.com>

>  arch/x86/kernel/smp.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
> index 20da354..4e44840 100644
> --- a/arch/x86/kernel/smp.c
> +++ b/arch/x86/kernel/smp.c
> @@ -118,9 +118,11 @@ static bool smp_no_nmi_ipi = false;
>  void ticket_spin_lock_wait(arch_spinlock_t *lock, struct __raw_tickets inc)
>  {
>  	for (;;) {
> -		cpu_relax();
> -		inc.head = ACCESS_ONCE(lock->tickets.head);
> +		int loops = 50 * (__ticket_t)(inc.tail - inc.head);
> +		while (loops--)
> +			cpu_relax();
>  
> +		inc.head = ACCESS_ONCE(lock->tickets.head);
>  		if (inc.head == inc.tail)
>  			break;
>  	}
> 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/