"multi-queue-max-queues" key not present on Xen host - is it possible to enable it?

"multi-queue-max-queues" key not present on Xen host - is it possible to enable it?

[Pawar, Sangram]

Hi,
My name is Sangram Pawar, a developer at NetApp. I'm currently measuring the performance of multi-queue support added to the netfront driver (in Jan'16).

I noticed the backend is not advertising the "multi-queue-max-queues" key. So whenever netfront driver (freebsd vm) checks for the "multi-queue-max-queues" key, it receives error 2 due to which it continues with the single queue.

# dmesg | grep Xen\ version
[    0.000000] Xen version: 4.3.0 (preserve-AD)

# uname -a
Linux xenhost 3.9.11-200.fc18.x86_64 #1 SMP Mon Jul 22 21:04:50 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

# xl info
host                   : xenhost
release                : 3.9.11-200.fc18.x86_64
version                : #1 SMP Mon Jul 22 21:04:50 UTC 2013
machine                : x86_64
nr_cpus                : 8
max_cpu_id             : 7
nr_nodes               : 2
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 2194
hw_caps                : bfebfbff:2c100800:00000000:00003f00:17bee3ff:00000000:00000001:00000000
virt_caps              : hvm hvm_directio
total_memory           : 24548
free_memory            : 452
sharing_freed_memory   : 0
sharing_used_memory    : 0
outstanding_claims     : 0
free_cpus              : 0
xen_major              : 4
xen_minor              : 3
xen_extra              : .0
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64 
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : 
xen_commandline        : placeholder
cc_compiler            : gcc (GCC) 4.7.2 20121109 (Red Hat 4.7.2-8)
cc_compile_by          : root
cc_compile_domain      : 
cc_compile_date        : Fri Mar 14 11:56:09 EDT 2014
xend_config_format     : 4



I followed the thread (http://lists.xenproject.org/archives/html/xen-devel/2013-06/msg02654.html) and noticed the dl at the bottom, so sending you few questions.


From this thread:
In addition to the feature flag, a backend which supports feature-multi-queue would advertise a maximum number of queues, via the key:
/local/domain/0/backend/vif/X/Y/multi-queue-max-queues

So it is clear that the backend doesn't support multi queue VIFs. Could you please tell the reason? Am I running too old Xen version? If yes, which Xen version has support for it? If not, is it possible to enable this feature so backend can advertise it using this key?

I appreciate your response here.


Thanks,
-- Sangram Pawar
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Re: "multi-queue-max-queues" key not present on Xen host - is it possible to enable it?

[Konrad Rzeszutek Wilk]

On Thu, Apr 28, 2016 at 07:34:32PM +0000, Pawar, Sangram wrote:
> Hi,
> My name is Sangram Pawar, a developer at NetApp. I'm currently measuring the performance of multi-queue support added to the netfront driver (in Jan'16).
> 
> I noticed the backend is not advertising the "multi-queue-max-queues" key. So whenever netfront driver (freebsd vm) checks for the "multi-queue-max-queues" key, it receives error 2 due to which it continues with the single queue.
> 
> # dmesg | grep Xen\ version
> [    0.000000] Xen version: 4.3.0 (preserve-AD)
> 
> # uname -a
> Linux xenhost 3.9.11-200.fc18.x86_64 #1 SMP Mon Jul 22 21:04:50 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
> 
> # xl info
> host                   : xenhost
> release                : 3.9.11-200.fc18.x86_64
> version                : #1 SMP Mon Jul 22 21:04:50 UTC 2013
> machine                : x86_64
> nr_cpus                : 8
> max_cpu_id             : 7
> nr_nodes               : 2
> cores_per_socket       : 4
> threads_per_core       : 1
> cpu_mhz                : 2194
> hw_caps                : bfebfbff:2c100800:00000000:00003f00:17bee3ff:00000000:00000001:00000000
> virt_caps              : hvm hvm_directio
> total_memory           : 24548
> free_memory            : 452
> sharing_freed_memory   : 0
> sharing_used_memory    : 0
> outstanding_claims     : 0
> free_cpus              : 0
> xen_major              : 4
> xen_minor              : 3
> xen_extra              : .0
> xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64 
> xen_scheduler          : credit
> xen_pagesize           : 4096
> platform_params        : virt_start=0xffff800000000000
> xen_changeset          : 
> xen_commandline        : placeholder
> cc_compiler            : gcc (GCC) 4.7.2 20121109 (Red Hat 4.7.2-8)
> cc_compile_by          : root
> cc_compile_domain      : 
> cc_compile_date        : Fri Mar 14 11:56:09 EDT 2014
> xend_config_format     : 4
> 
> 
> 
> I followed the thread (http://lists.xenproject.org/archives/html/xen-devel/2013-06/msg02654.html) and noticed the dl at the bottom, so sending you few questions.
> 
> 
> From this thread:
> In addition to the feature flag, a backend which supports feature-multi-queue would advertise a maximum number of queues, via the key:
> /local/domain/0/backend/vif/X/Y/multi-queue-max-queues
> 
> So it is clear that the backend doesn't support multi queue VIFs. Could you please tell the reason? Am I running too old Xen version? If yes, which Xen version has support for it? If not, is it possible to enable this feature so backend can advertise it using this key?
> 

It is your version of backend. Aka - the driver in Linux kernel.

I would recommend you upgrade to say 4.4.

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