[Xen-devel] libvirt support for scheduler credit2

[Xen-devel] libvirt support for scheduler credit2

[Kevin Stange]

Hi,

I looked around a bit and wasn't able to find a good answer to this, so
George suggested I ask here.

Since Xen 4.12, credit2 is the default scheduler, but at least as of
libvirt 5.1.0 virsh doesn't appear to understand credit2 and produces
this sort of output:

# xl sched-credit2 -d yw6hk7mo6zy3k8
Name                                ID Weight  Cap
yw6hk7mo6zy3k8                       4     10    0
# virsh schedinfo yw6hk7mo6zy3k8
Scheduler      : credit2

Compared to a host running credit:

# xl sched-credit -d gvz2b16sq38dv9
Name                                ID Weight  Cap
gvz2b16sq38dv9                      14    800    0
# virsh schedinfo gvz2b16sq38dv9
Scheduler      : credit
weight         : 800
cap            : 0

Trying to change the weight does nothing, not even producing an error
message:

# virsh schedinfo syuxplsmdihcwc --weight 300
Scheduler      : credit2

# xl sched-credit2 -d syuxplsmdihcwc
Name                                ID Weight  Cap
syuxplsmdihcwc                      23    400    0

Is there a version of libvirt where I can expect this to work, or is it
not supported yet?  As a workaround for now I've added sched=credit to
my command line, but it would be nice to gain the benefits of improved
scheduling at some point.

-- 
Kevin Stange
Chief Technology Officer
Steadfast | Managed Infrastructure, Datacenter and Cloud Services
800 S Wells, Suite 190 | Chicago, IL 60607
312.602.2689 X203 | Fax: 312.602.2688
kevin@steadfast.net | www.steadfast.net

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Re: [Xen-devel] libvirt support for scheduler credit2

[Jürgen Groß]

On 21.01.20 17:56, Kevin Stange wrote:
> Hi,
> 
> I looked around a bit and wasn't able to find a good answer to this, so
> George suggested I ask here.

Cc-ing Jim.

> 
> Since Xen 4.12, credit2 is the default scheduler, but at least as of
> libvirt 5.1.0 virsh doesn't appear to understand credit2 and produces
> this sort of output:
> 
> # xl sched-credit2 -d yw6hk7mo6zy3k8
> Name                                ID Weight  Cap
> yw6hk7mo6zy3k8                       4     10    0
> # virsh schedinfo yw6hk7mo6zy3k8
> Scheduler      : credit2
> 
> Compared to a host running credit:
> 
> # xl sched-credit -d gvz2b16sq38dv9
> Name                                ID Weight  Cap
> gvz2b16sq38dv9                      14    800    0
> # virsh schedinfo gvz2b16sq38dv9
> Scheduler      : credit
> weight         : 800
> cap            : 0
> 
> Trying to change the weight does nothing, not even producing an error
> message:
> 
> # virsh schedinfo syuxplsmdihcwc --weight 300
> Scheduler      : credit2
> 
> # xl sched-credit2 -d syuxplsmdihcwc
> Name                                ID Weight  Cap
> syuxplsmdihcwc                      23    400    0
> 
> Is there a version of libvirt where I can expect this to work, or is it
> not supported yet?  As a workaround for now I've added sched=credit to
> my command line, but it would be nice to gain the benefits of improved
> scheduling at some point.
> 


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Re: [Xen-devel] libvirt support for scheduler credit2

[Jim Fehlig]

On 1/21/20 10:05 AM, Jürgen Groß wrote:
> On 21.01.20 17:56, Kevin Stange wrote:
>> Hi,
>>
>> I looked around a bit and wasn't able to find a good answer to this, so
>> George suggested I ask here.
> 
> Cc-ing Jim.
> 
>>
>> Since Xen 4.12, credit2 is the default scheduler, but at least as of
>> libvirt 5.1.0 virsh doesn't appear to understand credit2 and produces
>> this sort of output:

You would see the same with libvirt.git master, sorry. ATM the libvirt libxl 
driver is unaware of the credit2 scheduler. Hmm, as I recall Dario was going to 
provide a patch for libvirt :-). But he is quite busy so it will have to be 
added to my very long todo list.

Regards,
Jim

>>
>> # xl sched-credit2 -d yw6hk7mo6zy3k8
>> Name                                ID Weight  Cap
>> yw6hk7mo6zy3k8                       4     10    0
>> # virsh schedinfo yw6hk7mo6zy3k8
>> Scheduler      : credit2
>>
>> Compared to a host running credit:
>>
>> # xl sched-credit -d gvz2b16sq38dv9
>> Name                                ID Weight  Cap
>> gvz2b16sq38dv9                      14    800    0
>> # virsh schedinfo gvz2b16sq38dv9
>> Scheduler      : credit
>> weight         : 800
>> cap            : 0
>>
>> Trying to change the weight does nothing, not even producing an error
>> message:
>>
>> # virsh schedinfo syuxplsmdihcwc --weight 300
>> Scheduler      : credit2
>>
>> # xl sched-credit2 -d syuxplsmdihcwc
>> Name                                ID Weight  Cap
>> syuxplsmdihcwc                      23    400    0
>>
>> Is there a version of libvirt where I can expect this to work, or is it
>> not supported yet?  As a workaround for now I've added sched=credit to
>> my command line, but it would be nice to gain the benefits of improved
>> scheduling at some point.
>>
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xenproject.org
> https://lists.xenproject.org/mailman/listinfo/xen-devel

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Re: [Xen-devel] libvirt support for scheduler credit2

[Kevin Stange]

On 1/22/20 12:56 PM, Jim Fehlig wrote:
> On 1/21/20 10:05 AM, Jürgen Groß wrote:
>> On 21.01.20 17:56, Kevin Stange wrote:
>>> Hi,
>>>
>>> I looked around a bit and wasn't able to find a good answer to this, so
>>> George suggested I ask here.
>>
>> Cc-ing Jim.
>>
>>>
>>> Since Xen 4.12, credit2 is the default scheduler, but at least as of
>>> libvirt 5.1.0 virsh doesn't appear to understand credit2 and produces
>>> this sort of output:
> 
> You would see the same with libvirt.git master, sorry. ATM the libvirt libxl 
> driver is unaware of the credit2 scheduler. Hmm, as I recall Dario was going to 
> provide a patch for libvirt :-). But he is quite busy so it will have to be 
> added to my very long todo list.

Sorry to hear that's the case.  Due to my orchestration system I'll have
to hang on to credit a while longer.  Thanks for clarifying!

-- 
Kevin Stange
Chief Technology Officer
Steadfast | Managed Infrastructure, Datacenter and Cloud Services
800 S Wells, Suite 190 | Chicago, IL 60607
312.602.2689 X203 | Fax: 312.602.2688
kevin@steadfast.net | www.steadfast.net

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Re: [Xen-devel] libvirt support for scheduler credit2

[Dario Faggioli]

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On Wed, 2020-01-22 at 18:56 +0000, Jim Fehlig wrote:
> On 1/21/20 10:05 AM, Jürgen Groß wrote:
> > On 21.01.20 17:56, Kevin Stange wrote:
> > > 
> > > Since Xen 4.12, credit2 is the default scheduler, but at least as
> > > of
> > > libvirt 5.1.0 virsh doesn't appear to understand credit2 and
> > > produces
> > > this sort of output:
> 
> You would see the same with libvirt.git master, sorry. ATM the
> libvirt libxl 
> driver is unaware of the credit2 scheduler. 
>
Right. I Just sent the patch:
https://www.redhat.com/archives/libvir-list/2020-January/msg01292.html

> Hmm, as I recall Dario was going to 
> provide a patch for libvirt :-). 
>
And in fact, back then, when Credit2 went default, I did check. I don't
recall now, I guess I checked the code and never properly tested
things.

And in the code (although, again, I don't remember the details) I must
have been tricked by the fact that since Credit and Credit2 have the
same parameters, libvirt handling of them is ok for both... And missed
the check that bails out if the scheduler is not Credit! :-/

Or something. IDK. Well, Sorry about that.

> But he is quite busy so it will have to be 
> added to my very long todo list.
>
I am, but this was an easy one, and was indeed my fault... So I did my
best. Hope the patch is not too terrible. :-)

Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
-------------------------------------------------------------------
<<This happens because _I_ choose it to happen!>> (Raistlin Majere)


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Re: [Xen-devel] libvirt support for scheduler credit2

[Jim Fehlig]

On 1/29/20 4:10 AM, Dario Faggioli wrote:
> On Wed, 2020-01-22 at 18:56 +0000, Jim Fehlig wrote:
>> On 1/21/20 10:05 AM, Jürgen Groß wrote:
>>> On 21.01.20 17:56, Kevin Stange wrote:
>>>>
>>>> Since Xen 4.12, credit2 is the default scheduler, but at least as
>>>> of
>>>> libvirt 5.1.0 virsh doesn't appear to understand credit2 and
>>>> produces
>>>> this sort of output:
>>
>> You would see the same with libvirt.git master, sorry. ATM the
>> libvirt libxl
>> driver is unaware of the credit2 scheduler.
>>
> Right. I Just sent the patch:
> https://www.redhat.com/archives/libvir-list/2020-January/msg01292.html

Thanks! I tweaked it a bit and committed to libvirt.git

https://libvirt.org/git/?p=libvirt.git;a=commit;h=849052ec61e18780713bec171748e859e32dfd6d

Regards,
Jim
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