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
| ||
|
Date: Tue, 23 Apr 2013 07:12:55 +0530 From: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com> To: Peter Zijlstra <peterz@...radead.org> CC: Rik van Riel <riel@...hat.com>, Jiannan Ouyang <ouyang@...pitt.edu>, LKML <linux-kernel@...r.kernel.org>, Avi Kivity <avi.kivity@...il.com>, Gleb Natapov <gleb@...hat.com>, Ingo Molnar <mingo@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>, Srikar <srikar@...ux.vnet.ibm.com>, "H. Peter Anvin" <hpa@...or.com>, "Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>, KVM <kvm@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, Chegu Vinod <chegu_vinod@...com>, "Andrew M. Theurer" <habanero@...ux.vnet.ibm.com>, Srivatsa Vaddagiri <srivatsa.vaddagiri@...il.com>, Andrew Jones <drjones@...hat.com>, Karen Noel <knoel@...hat.com> Subject: Re: Preemptable Ticket Spinlock On 04/23/2013 01:19 AM, Peter Zijlstra wrote: > On Mon, 2013-04-22 at 08:52 -0400, Rik van Riel wrote: >> On 04/22/2013 07:51 AM, Peter Zijlstra wrote: >>> On Sun, 2013-04-21 at 17:12 -0400, Rik van Riel wrote: >>>> >>>> If we always incremented the ticket number by 2 (instead of 1), then >>>> we could use the lower bit of the ticket number as the spinlock. >>> >>> ISTR that paravirt ticket locks already do that and use the lsb to >>> indicate the unlock needs to perform wakeups. >>> >>> Also, since all of this is virt nonsense, shouldn't it live in the >>> paravirt ticket lock code and leave the native code as is? >> >> Sure, but that is still no reason not to have the virt >> implementation be as fast as possible, and share the same >> data type as the non-virt implementation. > > It has to share the same data-type.. > >> Also, is it guaranteed that the native spin_lock code has >> not been called yet before we switch over to the paravirt >> functions? >> >> If the native spin_lock code has been called already at >> that time, the native code would still need to be modified >> to increment the ticket number by 2, so we end up with a >> compatible value in each spin lock's .tickets field, and >> prevent a deadlock after we switch over to the paravirt >> variant. > > I thought the stuff already made it upstream, but apparently not; the > lastest posting I'm aware of is here: > > https://lkml.org/lkml/2012/5/2/105 > > That stuff changes the normal ticket increment as well.. > pv-ticket spinlock went on hold state, after Avi acked because of: though on non-PLE, we get a huge advantage, on PLE machine the benefit was not as impressive (~10% as you stated in email chain) compared to the complexity of the patches. So Avi suggested to try PLE improvements first, so they are going upstream. https://lkml.org/lkml/2012/7/18/247 https://lkml.org/lkml/2013/1/22/104 https://lkml.org/lkml/2013/2/6/345 (on the way in kvm tree) Current status of PV spinlock: I have the rebased patches of pv spinlocks and experimenting with latest kernel.I have Gleb's irq delivery incorporated into the patch series. But I am thinknig whether I can improve some guest side logic in unlock. I will probably setup a githup and post the link soon. -- 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