linux-kernel - Re: [PATCH V3] perf & kvm: Enhance perf to collect KVM guest os statistics from host side

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <4BC596C5.7020507@redhat.com>
Date:	Wed, 14 Apr 2010 13:19:49 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Sheng Yang <sheng@...ux.intel.com>
CC:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	oerg Roedel <joro@...tes.org>,
	Jes Sorensen <Jes.Sorensen@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	Zachary Amsden <zamsden@...hat.com>, zhiteng.huang@...el.com,
	tim.c.chen@...el.com, Arnaldo Carvalho de Melo <acme@...radead.org>
Subject: Re: [PATCH V3] perf & kvm: Enhance perf to collect KVM guest os statistics
 from host side

On 04/14/2010 01:14 PM, Sheng Yang wrote:
>
>> I wouldn't like to depend on model specific behaviour.
>>
>> One option is to read all the information synchronously and store it in
>> a per-cpu area with atomic instructions, then queue the NMI.  Another
>> option is to have another callback which tells us that the NMI is done,
>> and have a busy loop wait until the NMI is delivered.
>>
>>      
> Callback seems too heavy, may affect the performance badly. Maybe a short
> queue would help, though this one is more complex.
>    

The patch we're replying to adds callbacks (to read rip, etc.), so it's 
no big deal.  For the queue solution, a queue of size one would probably 
be sufficient even if not guaranteed by the spec.  I don't see how the 
cpu can do another guest entry without delivering the NMI.

> But I am still curious if we extend the region, how much it would help. Would
> get a result soon...
>    

Yes, interesting to see what the latency is.  If it's reasonably short 
(and I expect it will be so), we can do the busy wait solution.

If we have an NMI counter somewhere, we can simply wait until it changes.

-- 
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/