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:	Sun, 30 Sep 2012 10:24:51 +0200
From:	Avi Kivity <avi@...hat.com>
To:	habanero@...ux.vnet.ibm.com
CC:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, Rik van Riel <riel@...hat.com>,
	Srikar <srikar@...ux.vnet.ibm.com>,
	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>,
	KVM <kvm@...r.kernel.org>, Jiannan Ouyang <ouyang@...pitt.edu>,
	chegu vinod <chegu_vinod@...com>,
	LKML <linux-kernel@...r.kernel.org>,
	Srivatsa Vaddagiri <srivatsa.vaddagiri@...il.com>,
	Gleb Natapov <gleb@...hat.com>,
	Andrew Jones <drjones@...hat.com>
Subject: Re: [PATCH RFC 0/2] kvm: Improving undercommit,overcommit scenarios
 in PLE handler

On 09/28/2012 01:40 PM, Andrew Theurer wrote:
>> 
>> >>
>> >> IIRC, with defer preemption :
>> >> we will have hook in spinlock/unlock path to measure depth of lock held,
>> >> and shared with host scheduler (may be via MSRs now).
>> >> Host scheduler 'prefers' not to preempt lock holding vcpu. (or rather
>> >> give say one chance.
>> >
>> > A downside is that we have to do that even when undercommitted.
> 
> Hopefully vcpu preemption is very rare when undercommitted, so it should
> not happen much at all.

As soon as you're preempted, you're effectively overcommitted (even if
the system as a whole is undercommitted).  What I meant was that you
need to communicate your lock state to the host, and with fine-grained
locking this can happen a lot.  It may be as simple as an
increment/decrement instruction though.



-- 
error compiling committee.c: too many arguments to function
--
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