* Rusty Russell <[EMAIL PROTECTED]> wrote:
> > so how can both "Xen and lhype get native syscall speeds (within
> > measurement error)", if it cannot use SYSENTER (it has to use int
> > $0x80), while a HVM kernel can?
>
> Sorry, my mistake. I was measuring with a statically linked binary,
>
On Thu, 2007-01-11 at 03:51 +0100, Ingo Molnar wrote:
> * Rusty Russell <[EMAIL PROTECTED]> wrote:
>
> > > > Err no, this isn't true. See Documentation/lhype.txt or various blog
> > > > entries on the subject 8) Both Xen and lhype get native syscall speeds
> > > > (within measurement error).
>
* Rusty Russell <[EMAIL PROTECTED]> wrote:
> > > Err no, this isn't true. See Documentation/lhype.txt or various blog
> > > entries on the subject 8) Both Xen and lhype get native syscall speeds
> > > (within measurement error).
> >
> > i was talking about 64-bit. (we dont really design for 3
On Thu, 2007-01-11 at 01:49 +0100, Ingo Molnar wrote:
> * Rusty Russell <[EMAIL PROTECTED]> wrote:
>
> > > > - cr3 switches for CONFIG_PARAVIRT syscalls (which are necessary
> > > > on x86_64) will probably become very cheap with tagged tlbs
> > >
> > > but irq overhead is nothing in importance
* Rusty Russell <[EMAIL PROTECTED]> wrote:
> > > - cr3 switches for CONFIG_PARAVIRT syscalls (which are necessary
> > > on x86_64) will probably become very cheap with tagged tlbs
> >
> > but irq overhead is nothing in importance compared to basic syscall
> > overhead. KVM/HVM already runs gue
On Wed, 2007-01-10 at 11:52 +0100, Ingo Molnar wrote:
> * Avi Kivity <[EMAIL PROTECTED]> wrote:
>
> > If you have a CONFIG_PARAVIRT guest, I believe it will always be
> > faster to run it without hardware assisted virtualization:
> >
> > - you cannot eliminate vmexits due to host interrupts
> >
Ulrich Drepper wrote:
> Avi Kivity wrote:
>
>> [[Can't a paravirtualized kernel use a vdso to use int $0x80 instead of
>> syscall?]]
>>
>
> No. The ABI is to inline syscall instructions. That's possible since
> it's not as limited/broken as sysenter.
>
Then maybe kvm+npt+paravirt can
Avi Kivity wrote:
> [[Can't a paravirtualized kernel use a vdso to use int $0x80 instead of
> syscall?]]
No. The ABI is to inline syscall instructions. That's possible since
it's not as limited/broken as sysenter.
--
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖
sig
Ulrich Drepper wrote:
> Ingo Molnar wrote:
>
>> that alone is already ~100-200 cycles overhead, it essentially doubles
>> the null syscall overhead. It matters at millions of syscalls per second
>> workloads, 100 cycles overhead at 1 million syscalls a second means 5%
>> performance differenc
Ingo Molnar wrote:
> that alone is already ~100-200 cycles overhead, it essentially doubles
> the null syscall overhead. It matters at millions of syscalls per second
> workloads, 100 cycles overhead at 1 million syscalls a second means 5%
> performance difference at 2GHz.
Plus, x86-64 uses onl
Anthony Liguori wrote:
> Avi Kivity wrote:
>> Ingo Molnar wrote:
>>
>>> * Avi Kivity <[EMAIL PROTECTED]> wrote:
>>>
>>>
>>>
If you have a CONFIG_PARAVIRT guest, I believe it will always be
faster to run it without hardware assisted virtualization:
- you cannot eliminate vm
Avi Kivity wrote:
> Ingo Molnar wrote:
>
>> * Avi Kivity <[EMAIL PROTECTED]> wrote:
>>
>>
>>
>>> If you have a CONFIG_PARAVIRT guest, I believe it will always be
>>> faster to run it without hardware assisted virtualization:
>>>
>>> - you cannot eliminate vmexits due to host interrupts
>>>
Ingo Molnar wrote:
> * Avi Kivity <[EMAIL PROTECTED]> wrote:
>
>
>> For i386 Xen does not switch cr3 IIRC. [...]
>>
>
> correct.
>
>
>> [...] Perhaps even not for x86_64 if it can use the segment limits
>> which AMD re-added (I think it does?)
>>
>
> i'm not sure. Older ones defini
* Avi Kivity <[EMAIL PROTECTED]> wrote:
> For i386 Xen does not switch cr3 IIRC. [...]
correct.
> [...] Perhaps even not for x86_64 if it can use the segment limits
> which AMD re-added (I think it does?)
i'm not sure. Older ones definitely used cr3 switching and on Intel
there's no segment
Ingo Molnar wrote:
> * Avi Kivity <[EMAIL PROTECTED]> wrote:
>
>
>> If you have a CONFIG_PARAVIRT guest, I believe it will always be
>> faster to run it without hardware assisted virtualization:
>>
>> - you cannot eliminate vmexits due to host interrupts
>> - a hypercall will (probably) keep be
Hello all,
hard and software virtualisation has been with us since the mid 1960's, as
I am sure you are all aware of.
See http://en.wikipedia.org/wiki/VM/CMS
JC
On Wed, January 10, 2007 11:46, Rusty Russell wrote:
> On Wed, 2007-01-10 at 10:47 +0100, Ingo Molnar wrote:
>
>> * Rusty Russell <[
* Avi Kivity <[EMAIL PROTECTED]> wrote:
> If you have a CONFIG_PARAVIRT guest, I believe it will always be
> faster to run it without hardware assisted virtualization:
>
> - you cannot eliminate vmexits due to host interrupts
> - a hypercall will (probably) keep being more expensive than a sysc
On Wed, 2007-01-10 at 10:47 +0100, Ingo Molnar wrote:
> * Rusty Russell <[EMAIL PROTECTED]> wrote:
> regarding ABI: agreed that it's experimental right now and should stay
> so for some time, but i dont see a reason why the hypercall API that
> i've posted in the past few days couldnt be evolved
Ingo Molnar wrote:
> * Ulrich Drepper <[EMAIL PROTECTED]> wrote:
>
>
>> Ingo Molnar wrote:
>>
>>> i really really think KVM and lhype should merge, creating KVM/HVM
>>> (Hardware Virtual Machine) and KVM/LL (Linux on Linux).
>>>
>> This is only sufficient if either KVM with paravirt
* Ulrich Drepper <[EMAIL PROTECTED]> wrote:
> Ingo Molnar wrote:
> > i really really think KVM and lhype should merge, creating KVM/HVM
> > (Hardware Virtual Machine) and KVM/LL (Linux on Linux).
>
> This is only sufficient if either KVM with paravirt Linux kernels has
> no performance penalty
Ingo Molnar wrote:
> i really really think KVM and lhype should merge, creating KVM/HVM
> (Hardware Virtual Machine) and KVM/LL (Linux on Linux).
This is only sufficient if either KVM with paravirt Linux kernels has no
performance penalty or lhype becomes able to execute paravirt Linux kernels.
* Rusty Russell <[EMAIL PROTECTED]> wrote:
> > It's also something for the Linux community in general to decide: if
> > we want separate interfaces for paravirtualization and full
> > virtualization (lhype and kvm) or a merged interface. I can see
> > arguments in favor of both positions.
>
On Tue, 2007-01-09 at 16:27 +0200, Avi Kivity wrote:
> Hugo Mills wrote:
> >Does running paravirtual guests on KVM still require a
> > hardware-VM-capable processor, or will it eventually be possible to
> > run a paravirtualised Linux on an older machine (such as, say, a
> > first-generation At
Hugo Mills wrote:
>I'm a little unclear on the capabilities (current or planned) of
> the new paravirtualisation feature in KVM.
>
>Does running paravirtual guests on KVM still require a
> hardware-VM-capable processor, or will it eventually be possible to
> run a paravirtualised Linux on a
24 matches
Mail list logo
