[PATCH 0/2] limit xen vnic max queues number to online cpu number

[PATCH 0/2] limit xen vnic max queues number to online cpu number

[Joe Jin]

Currently xen vnic allowed to create lots of queues by set module param
max_queues(both netback and netfront), when queues number larger than
cpu number, it does not help for performance but need more cpu time.

This patchset limit netback and netfront max queues number to online
cpus number.

Joe Jin (2):
  xen-netback: limit xen vif max queues number to online cpus
  xen-front: limit vnic max_queues number to online cpus

 drivers/net/xen-netback/netback.c |   28 ++++++++++++++++++++++------
 drivers/net/xen-netfront.c        |   27 +++++++++++++++++++++------
 2 files changed, 43 insertions(+), 12 deletions(-)

RE: [PATCH 0/2] limit xen vnic max queues number to online cpu number

[Paul Durrant]

> -----Original Message-----
> From: Joe Jin [mailto:joe.jin@oracle.com]
> Sent: 23 October 2015 10:05
> To: Paul Durrant; Wei Liu; Ian Campbell; Boris Ostrovsky; Konrad Rzeszutek
> Wilk; David S. Miller
> Cc: netdev@vger.kernel.org; xen-devel@lists.xenproject.org
> Subject: Re: [PATCH 0/2] limit xen vnic max queues number to online cpu
> number
> 
> On 10/23/2015 04:47 PM, Paul Durrant wrote:
> >> -----Original Message-----
> >> From: netdev-owner@vger.kernel.org [mailto:netdev-
> >> owner@vger.kernel.org] On Behalf Of Joe Jin
> >> Sent: 23 October 2015 08:54
> >> To: Wei Liu; Ian Campbell; Boris Ostrovsky; Konrad Rzeszutek Wilk; David
> S.
> >> Miller
> >> Cc: netdev@vger.kernel.org; xen-devel@lists.xenproject.org
> >> Subject: [PATCH 0/2] limit xen vnic max queues number to online cpu
> >> number
> >>
> >> Currently xen vnic allowed to create lots of queues by set module param
> >> max_queues(both netback and netfront), when queues number larger
> than
> >> cpu number, it does not help for performance but need more cpu time.
> >>
> >
> > But it's an override, so why would you want to limit it? The parameter
> should not be set in the common case.
> 
> Always we can not stop people use it because we provided it :)
> 

Indeed, and I believe it was provided largely for test purposes... to force the limit to whatever the admin wants.

> If queues number is larger than cpu number, with heavy network load,
> cpus have to take more time for interrupt, this lead others less
> chance to be scheduled.
> Imaging dom0 have 64 cpus, and assigned 4 vcpus to the guest, if
> set max_queues to 64 on guest, it will consumed more cpu times
> and bandwidth on backend, I think this is not we expected?
> 

I think that would be entirely expected.

  Paul

> Thanks,
> Joe
> >
> >   Paul
> >
> >> This patchset limit netback and netfront max queues number to online
> >> cpus number.
> >>
> >> Joe Jin (2):
> >>   xen-netback: limit xen vif max queues number to online cpus
> >>   xen-front: limit vnic max_queues number to online cpus
> >>
> >>  drivers/net/xen-netback/netback.c |   28 ++++++++++++++++++++++---
> ---
> >>  drivers/net/xen-netfront.c        |   27 +++++++++++++++++++++------
> >>  2 files changed, 43 insertions(+), 12 deletions(-)
> >>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe netdev" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 0/2] limit xen vnic max queues number to online cpu number

[Paul Durrant]

> -----Original Message-----
> From: Joe Jin [mailto:joe.jin@oracle.com]
> Sent: 23 October 2015 10:05
> To: Paul Durrant; Wei Liu; Ian Campbell; Boris Ostrovsky; Konrad Rzeszutek
> Wilk; David S. Miller
> Cc: netdev@vger.kernel.org; xen-devel@lists.xenproject.org
> Subject: Re: [PATCH 0/2] limit xen vnic max queues number to online cpu
> number
> 
> On 10/23/2015 04:47 PM, Paul Durrant wrote:
> >> -----Original Message-----
> >> From: netdev-owner@vger.kernel.org [mailto:netdev-
> >> owner@vger.kernel.org] On Behalf Of Joe Jin
> >> Sent: 23 October 2015 08:54
> >> To: Wei Liu; Ian Campbell; Boris Ostrovsky; Konrad Rzeszutek Wilk; David
> S.
> >> Miller
> >> Cc: netdev@vger.kernel.org; xen-devel@lists.xenproject.org
> >> Subject: [PATCH 0/2] limit xen vnic max queues number to online cpu
> >> number
> >>
> >> Currently xen vnic allowed to create lots of queues by set module param
> >> max_queues(both netback and netfront), when queues number larger
> than
> >> cpu number, it does not help for performance but need more cpu time.
> >>
> >
> > But it's an override, so why would you want to limit it? The parameter
> should not be set in the common case.
> 
> Always we can not stop people use it because we provided it :)
> 

Indeed, and I believe it was provided largely for test purposes... to force the limit to whatever the admin wants.

> If queues number is larger than cpu number, with heavy network load,
> cpus have to take more time for interrupt, this lead others less
> chance to be scheduled.
> Imaging dom0 have 64 cpus, and assigned 4 vcpus to the guest, if
> set max_queues to 64 on guest, it will consumed more cpu times
> and bandwidth on backend, I think this is not we expected?
> 

I think that would be entirely expected.

  Paul

> Thanks,
> Joe
> >
> >   Paul
> >
> >> This patchset limit netback and netfront max queues number to online
> >> cpus number.
> >>
> >> Joe Jin (2):
> >>   xen-netback: limit xen vif max queues number to online cpus
> >>   xen-front: limit vnic max_queues number to online cpus
> >>
> >>  drivers/net/xen-netback/netback.c |   28 ++++++++++++++++++++++---
> ---
> >>  drivers/net/xen-netfront.c        |   27 +++++++++++++++++++++------
> >>  2 files changed, 43 insertions(+), 12 deletions(-)
> >>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe netdev" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 0/2] limit xen vnic max queues number to online cpu number

[Jan Beulich]

>>> On 23.10.15 at 11:05, <joe.jin@oracle.com> wrote:
> On 10/23/2015 04:47 PM, Paul Durrant wrote:
>>> -----Original Message-----
>>> From: netdev-owner@vger.kernel.org [mailto:netdev-
>>> owner@vger.kernel.org] On Behalf Of Joe Jin
>>> Sent: 23 October 2015 08:54
>>> To: Wei Liu; Ian Campbell; Boris Ostrovsky; Konrad Rzeszutek Wilk; David S.
>>> Miller
>>> Cc: netdev@vger.kernel.org; xen-devel@lists.xenproject.org 
>>> Subject: [PATCH 0/2] limit xen vnic max queues number to online cpu
>>> number
>>>
>>> Currently xen vnic allowed to create lots of queues by set module param
>>> max_queues(both netback and netfront), when queues number larger than
>>> cpu number, it does not help for performance but need more cpu time.
>>>
>> 
>> But it's an override, so why would you want to limit it? The parameter 
> should not be set in the common case.
> 
> Always we can not stop people use it because we provided it :)

Well, it's always a question of whether preventing the admin to
shoot himself in the foot makes sense: When it leads to an unusable
system, it probably does. When it leads to a sub-optimal working
system, perhaps we should allow them their freedom?

Jan

Re: [PATCH 0/2] limit xen vnic max queues number to online cpu number

[Joe Jin]

On 10/23/2015 04:47 PM, Paul Durrant wrote:
>> -----Original Message-----
>> From: netdev-owner@vger.kernel.org [mailto:netdev-
>> owner@vger.kernel.org] On Behalf Of Joe Jin
>> Sent: 23 October 2015 08:54
>> To: Wei Liu; Ian Campbell; Boris Ostrovsky; Konrad Rzeszutek Wilk; David S.
>> Miller
>> Cc: netdev@vger.kernel.org; xen-devel@lists.xenproject.org
>> Subject: [PATCH 0/2] limit xen vnic max queues number to online cpu
>> number
>>
>> Currently xen vnic allowed to create lots of queues by set module param
>> max_queues(both netback and netfront), when queues number larger than
>> cpu number, it does not help for performance but need more cpu time.
>>
> 
> But it's an override, so why would you want to limit it? The parameter should not be set in the common case.

Always we can not stop people use it because we provided it :)

If queues number is larger than cpu number, with heavy network load,
cpus have to take more time for interrupt, this lead others less
chance to be scheduled.
Imaging dom0 have 64 cpus, and assigned 4 vcpus to the guest, if
set max_queues to 64 on guest, it will consumed more cpu times
and bandwidth on backend, I think this is not we expected?

Thanks,
Joe
> 
>   Paul
> 
>> This patchset limit netback and netfront max queues number to online
>> cpus number.
>>
>> Joe Jin (2):
>>   xen-netback: limit xen vif max queues number to online cpus
>>   xen-front: limit vnic max_queues number to online cpus
>>
>>  drivers/net/xen-netback/netback.c |   28 ++++++++++++++++++++++------
>>  drivers/net/xen-netfront.c        |   27 +++++++++++++++++++++------
>>  2 files changed, 43 insertions(+), 12 deletions(-)
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe netdev" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 0/2] limit xen vnic max queues number to online cpu number

[Joe Jin]

On 10/23/2015 04:47 PM, Paul Durrant wrote:
>> -----Original Message-----
>> From: netdev-owner@vger.kernel.org [mailto:netdev-
>> owner@vger.kernel.org] On Behalf Of Joe Jin
>> Sent: 23 October 2015 08:54
>> To: Wei Liu; Ian Campbell; Boris Ostrovsky; Konrad Rzeszutek Wilk; David S.
>> Miller
>> Cc: netdev@vger.kernel.org; xen-devel@lists.xenproject.org
>> Subject: [PATCH 0/2] limit xen vnic max queues number to online cpu
>> number
>>
>> Currently xen vnic allowed to create lots of queues by set module param
>> max_queues(both netback and netfront), when queues number larger than
>> cpu number, it does not help for performance but need more cpu time.
>>
> 
> But it's an override, so why would you want to limit it? The parameter should not be set in the common case.

Always we can not stop people use it because we provided it :)

If queues number is larger than cpu number, with heavy network load,
cpus have to take more time for interrupt, this lead others less
chance to be scheduled.
Imaging dom0 have 64 cpus, and assigned 4 vcpus to the guest, if
set max_queues to 64 on guest, it will consumed more cpu times
and bandwidth on backend, I think this is not we expected?

Thanks,
Joe
> 
>   Paul
> 
>> This patchset limit netback and netfront max queues number to online
>> cpus number.
>>
>> Joe Jin (2):
>>   xen-netback: limit xen vif max queues number to online cpus
>>   xen-front: limit vnic max_queues number to online cpus
>>
>>  drivers/net/xen-netback/netback.c |   28 ++++++++++++++++++++++------
>>  drivers/net/xen-netfront.c        |   27 +++++++++++++++++++++------
>>  2 files changed, 43 insertions(+), 12 deletions(-)
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe netdev" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html

RE: [PATCH 0/2] limit xen vnic max queues number to online cpu number

[Paul Durrant]

> -----Original Message-----
> From: netdev-owner@vger.kernel.org [mailto:netdev-
> owner@vger.kernel.org] On Behalf Of Joe Jin
> Sent: 23 October 2015 08:54
> To: Wei Liu; Ian Campbell; Boris Ostrovsky; Konrad Rzeszutek Wilk; David S.
> Miller
> Cc: netdev@vger.kernel.org; xen-devel@lists.xenproject.org
> Subject: [PATCH 0/2] limit xen vnic max queues number to online cpu
> number
> 
> Currently xen vnic allowed to create lots of queues by set module param
> max_queues(both netback and netfront), when queues number larger than
> cpu number, it does not help for performance but need more cpu time.
> 

But it's an override, so why would you want to limit it? The parameter should not be set in the common case.

  Paul

> This patchset limit netback and netfront max queues number to online
> cpus number.
> 
> Joe Jin (2):
>   xen-netback: limit xen vif max queues number to online cpus
>   xen-front: limit vnic max_queues number to online cpus
> 
>  drivers/net/xen-netback/netback.c |   28 ++++++++++++++++++++++------
>  drivers/net/xen-netfront.c        |   27 +++++++++++++++++++++------
>  2 files changed, 43 insertions(+), 12 deletions(-)
> 
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 0/2] limit xen vnic max queues number to online cpu number

[Paul Durrant]

> -----Original Message-----
> From: netdev-owner@vger.kernel.org [mailto:netdev-
> owner@vger.kernel.org] On Behalf Of Joe Jin
> Sent: 23 October 2015 08:54
> To: Wei Liu; Ian Campbell; Boris Ostrovsky; Konrad Rzeszutek Wilk; David S.
> Miller
> Cc: netdev@vger.kernel.org; xen-devel@lists.xenproject.org
> Subject: [PATCH 0/2] limit xen vnic max queues number to online cpu
> number
> 
> Currently xen vnic allowed to create lots of queues by set module param
> max_queues(both netback and netfront), when queues number larger than
> cpu number, it does not help for performance but need more cpu time.
> 

But it's an override, so why would you want to limit it? The parameter should not be set in the common case.

  Paul

> This patchset limit netback and netfront max queues number to online
> cpus number.
> 
> Joe Jin (2):
>   xen-netback: limit xen vif max queues number to online cpus
>   xen-front: limit vnic max_queues number to online cpus
> 
>  drivers/net/xen-netback/netback.c |   28 ++++++++++++++++++++++------
>  drivers/net/xen-netfront.c        |   27 +++++++++++++++++++++------
>  2 files changed, 43 insertions(+), 12 deletions(-)
> 
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

[PATCH 0/2] limit xen vnic max queues number to online cpu number

[Joe Jin]

Currently xen vnic allowed to create lots of queues by set module param
max_queues(both netback and netfront), when queues number larger than
cpu number, it does not help for performance but need more cpu time.

This patchset limit netback and netfront max queues number to online
cpus number.

Joe Jin (2):
  xen-netback: limit xen vif max queues number to online cpus
  xen-front: limit vnic max_queues number to online cpus

 drivers/net/xen-netback/netback.c |   28 ++++++++++++++++++++++------
 drivers/net/xen-netfront.c        |   27 +++++++++++++++++++++------
 2 files changed, 43 insertions(+), 12 deletions(-)