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  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Mon, 7 Jul 2008 15:46:51 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Christoph Lameter <clameter@....com>,
	Petr Tesarik <ptesarik@...e.cz>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, Nick Piggin <nickpiggin@...oo.com.au>
Subject: Re: Spinlocks: Factor our GENERIC_LOCKBREAK in order to avoid spin
 with irqs disable

On Wed, 25 Jun 2008 19:51:12 -0700
Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Thomas Friebel presented results at the Xen Summit this week showing 
> that ticket locks are an absolute disaster for scalability in a virtual 
> environment, for a similar reason.  It's a bit irritating if the lock 
> holder vcpu gets preempted by the hypervisor, but its much worse when 
> they release the lock: unless the vcpu scheduler gives a cpu to the vcpu 
> with the next ticket, it can waste up to N timeslices spinning.
> 
> I'm experimenting with adding pvops hook to allow you to put in new 
> spinlock implementations on the fly.

Alternatively, the guest could tell the host which vcpus
are next in line for a ticket spinlock, or a vcpu that gets
scheduled but is not supposed to grab the lock yet can give
some CPU time to the vcpu that should get the lock next.

I believe the IBM PPC64 people have done some work to implement
just that.

-- 
All Rights Reversed
--
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/

Powered by blists - more mailing lists