Another question

Another question

[Christoffer Dall]

Hi guys,

I have an x86 question that I really hope you can help with:

Running the kvm-unit-tests on x86, I see a quite large difference
between I/O from the kernel, and I/O user (around 6,000 cycles) on two
separate platforms.

This is probably expected, but what is the explanation? If I correlate
with system call overhead from lmbench, it's nowhere near that (in the
hundreds of cycles), so I'm sure I'm missing something obvious.

Thanks!
-Christoffer

Re: Another question

[Gleb Natapov]

On Tue, Mar 26, 2013 at 09:57:00AM -0700, Christoffer Dall wrote:
> Hi guys,
> 
> I have an x86 question that I really hope you can help with:
> 
> Running the kvm-unit-tests on x86, I see a quite large difference
> between I/O from the kernel, and I/O user (around 6,000 cycles) on two
> separate platforms.
> 
> This is probably expected, but what is the explanation? If I correlate
> with system call overhead from lmbench, it's nowhere near that (in the
> hundreds of cycles), so I'm sure I'm missing something obvious.
> 
KVM does not restore full CPU host state on each vmexit since not all
the state is used by the kernel while KVM is running on the CPU. Some
state is restored only when vcpu thread is scheduled out from a host CPU
and some state is restored only when CPU moves to userspace. To exit to
userspace full host CPU state need to be restored.

--
			Gleb.

Another Question

[Richard Mayo]

I should have posted this question along with my previous posting, but
these things happen. . .

While running in enforcing mode, is it possible to allow certain actions,
but still to audit their occurences?
(perhaps with some command working the opposite of "neveraudit")


I appreciate any assistance,
Rich Mayo



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Re: Another Question

[Russell Coker]

On Mon, 9 Dec 2002 18:53, Richard Mayo wrote:
> While running in enforcing mode, is it possible to allow certain actions,
> but still to audit their occurences?

auditallow.

> (perhaps with some command working the opposite of "neveraudit")

dontaudit.


These are used in the sample policy.  dontaudit is a newer addition so it's 
not in the earlier documents, but it should be in the latest doco, auditallow 
is well documented.

-- 
http://www.coker.com.au/selinux/   My NSA Security Enhanced Linux packages
http://www.coker.com.au/bonnie++/  Bonnie++ hard drive benchmark
http://www.coker.com.au/postal/    Postal SMTP/POP benchmark
http://www.coker.com.au/~russell/  My home page


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another question.....

[Neil Horman]

hey again all!
	I also had a question regarding the swapper_pg_dir variable.  I understand that
it is used as a sort of private cache for kernel tasks (kswapd, klogd, etc).  I
was wondering, is that area used only for kernel threads, or for all threads
executing in kernel space? (I.E. user processes in a system call, etc)?  Many
thanks!
Neil

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Re: another question.....

[Dan Malek]

Neil Horman wrote:

> 	I also had a question regarding the swapper_pg_dir variable.

It's used to represent the kernel mapping.  The combination of the
kernel mapping and that of the current application memory context will
determine how memory is accessed.


	-- Dan


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