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Re: [PATCH v3 2/9] xen-block: add document for mutli hardware queues/rings

Started byRoger Pau Monné <roger.pau@citrix.com>
First post2015-10-02 18:10 +0200
Last post2015-10-03 02:00 +0200
Articles 4 — 3 participants

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  Re: [PATCH v3 2/9] xen-block: add document for mutli hardware  queues/rings Roger Pau Monné <roger.pau@citrix.com> - 2015-10-02 18:10 +0200
    Re: [Xen-devel] [PATCH v3 2/9] xen-block: add document for mutli  hardware queues/rings Wei Liu <wei.liu2@citrix.com> - 2015-10-02 18:20 +0200
      Re: [Xen-devel] [PATCH v3 2/9] xen-block: add document for mutli  hardware queues/rings Roger Pau Monné <roger.pau@citrix.com> - 2015-10-02 18:30 +0200
        Re: [Xen-devel] [PATCH v3 2/9] xen-block: add document for mutli  hardware queues/rings Bob Liu <bob.liu@oracle.com> - 2015-10-03 02:00 +0200

#1238381 — Re: [PATCH v3 2/9] xen-block: add document for mutli hardware queues/rings

FromRoger Pau Monné <roger.pau@citrix.com>
Date2015-10-02 18:10 +0200
SubjectRe: [PATCH v3 2/9] xen-block: add document for mutli hardware queues/rings
Message-ID<qfb4d-8hp-7@gated-at.bofh.it>
El 05/09/15 a les 14.39, Bob Liu ha escrit:
> Document multi queues/rings of xen-block.
> 
> Signed-off-by: Bob Liu <bob.liu@oracle.com>

As said by Konrad, you should send this against the Xen public headers
also (or even before). I have a comment below.

> ---
>  include/xen/interface/io/blkif.h |   32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/include/xen/interface/io/blkif.h b/include/xen/interface/io/blkif.h
> index c33e1c4..b453b70 100644
> --- a/include/xen/interface/io/blkif.h
> +++ b/include/xen/interface/io/blkif.h
> @@ -28,6 +28,38 @@ typedef uint16_t blkif_vdev_t;
>  typedef uint64_t blkif_sector_t;
>  
>  /*
> + * Multiple hardware queues/rings:
> + * If supported, the backend will write the key "multi-queue-max-queues" to
> + * the directory for that vbd, and set its value to the maximum supported
> + * number of queues.
> + * Frontends that are aware of this feature and wish to use it can write the
> + * key "multi-queue-num-queues", set to the number they wish to use, which
> + * must be greater than zero, and no more than the value reported by the backend
> + * in "multi-queue-max-queues".
> + *
> + * For frontends requesting just one queue, the usual event-channel and
> + * ring-ref keys are written as before, simplifying the backend processing
> + * to avoid distinguishing between a frontend that doesn't understand the
> + * multi-queue feature, and one that does, but requested only one queue.
> + *
> + * Frontends requesting two or more queues must not write the toplevel
> + * event-channeland ring-ref keys, instead writing those keys under sub-keys
> + * having the name "queue-N" where N is the integer ID of the queue/ring for
> + * which those keys belong. Queues are indexed from zero.
> + * For example, a frontend with two queues must write the following set of
> + * queue-related keys:
> + *
> + * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2"
> + * /local/domain/1/device/vbd/0/queue-0 = ""
> + * /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref>"
> + * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn>"
> + * /local/domain/1/device/vbd/0/queue-1 = ""
> + * /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref>"
> + * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn>"

AFAICT, it's impossible by design to use multiple queues together with
multipage rings, is that right?

Roger.

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#1238384 — Re: [Xen-devel] [PATCH v3 2/9] xen-block: add document for mutli hardware queues/rings

FromWei Liu <wei.liu2@citrix.com>
Date2015-10-02 18:20 +0200
SubjectRe: [Xen-devel] [PATCH v3 2/9] xen-block: add document for mutli hardware queues/rings
Message-ID<qfbdU-8tf-3@gated-at.bofh.it>
In reply to#1238381
On Fri, Oct 02, 2015 at 06:04:35PM +0200, Roger Pau Monné wrote:
> El 05/09/15 a les 14.39, Bob Liu ha escrit:
> > Document multi queues/rings of xen-block.
> > 
> > Signed-off-by: Bob Liu <bob.liu@oracle.com>
> 
> As said by Konrad, you should send this against the Xen public headers
> also (or even before). I have a comment below.
> 
> > ---
> >  include/xen/interface/io/blkif.h |   32 ++++++++++++++++++++++++++++++++
> >  1 file changed, 32 insertions(+)
> > 
> > diff --git a/include/xen/interface/io/blkif.h b/include/xen/interface/io/blkif.h
> > index c33e1c4..b453b70 100644
> > --- a/include/xen/interface/io/blkif.h
> > +++ b/include/xen/interface/io/blkif.h
> > @@ -28,6 +28,38 @@ typedef uint16_t blkif_vdev_t;
> >  typedef uint64_t blkif_sector_t;
> >  
> >  /*
> > + * Multiple hardware queues/rings:
> > + * If supported, the backend will write the key "multi-queue-max-queues" to
> > + * the directory for that vbd, and set its value to the maximum supported
> > + * number of queues.
> > + * Frontends that are aware of this feature and wish to use it can write the
> > + * key "multi-queue-num-queues", set to the number they wish to use, which
> > + * must be greater than zero, and no more than the value reported by the backend
> > + * in "multi-queue-max-queues".
> > + *
> > + * For frontends requesting just one queue, the usual event-channel and
> > + * ring-ref keys are written as before, simplifying the backend processing
> > + * to avoid distinguishing between a frontend that doesn't understand the
> > + * multi-queue feature, and one that does, but requested only one queue.
> > + *
> > + * Frontends requesting two or more queues must not write the toplevel
> > + * event-channeland ring-ref keys, instead writing those keys under sub-keys
> > + * having the name "queue-N" where N is the integer ID of the queue/ring for
> > + * which those keys belong. Queues are indexed from zero.
> > + * For example, a frontend with two queues must write the following set of
> > + * queue-related keys:
> > + *
> > + * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2"
> > + * /local/domain/1/device/vbd/0/queue-0 = ""
> > + * /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref>"
> > + * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn>"
> > + * /local/domain/1/device/vbd/0/queue-1 = ""
> > + * /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref>"
> > + * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn>"
> 
> AFAICT, it's impossible by design to use multiple queues together with
> multipage rings, is that right?
> 

As far as I can tell, these two features are not inherently coupled.
Whether you want to make (by design) them coupled together or not is
another matter. :-)

> Roger.
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel
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#1238395 — Re: [Xen-devel] [PATCH v3 2/9] xen-block: add document for mutli hardware queues/rings

FromRoger Pau Monné <roger.pau@citrix.com>
Date2015-10-02 18:30 +0200
SubjectRe: [Xen-devel] [PATCH v3 2/9] xen-block: add document for mutli hardware queues/rings
Message-ID<qfbnB-cS-31@gated-at.bofh.it>
In reply to#1238384
El 02/10/15 a les 18.12, Wei Liu ha escrit:
> On Fri, Oct 02, 2015 at 06:04:35PM +0200, Roger Pau Monné wrote:
>> El 05/09/15 a les 14.39, Bob Liu ha escrit:
>>> Document multi queues/rings of xen-block.
>>>
>>> Signed-off-by: Bob Liu <bob.liu@oracle.com>
>>
>> As said by Konrad, you should send this against the Xen public headers
>> also (or even before). I have a comment below.
>>
>>> ---
>>>  include/xen/interface/io/blkif.h |   32 ++++++++++++++++++++++++++++++++
>>>  1 file changed, 32 insertions(+)
>>>
>>> diff --git a/include/xen/interface/io/blkif.h b/include/xen/interface/io/blkif.h
>>> index c33e1c4..b453b70 100644
>>> --- a/include/xen/interface/io/blkif.h
>>> +++ b/include/xen/interface/io/blkif.h
>>> @@ -28,6 +28,38 @@ typedef uint16_t blkif_vdev_t;
>>>  typedef uint64_t blkif_sector_t;
>>>  
>>>  /*
>>> + * Multiple hardware queues/rings:
>>> + * If supported, the backend will write the key "multi-queue-max-queues" to
>>> + * the directory for that vbd, and set its value to the maximum supported
>>> + * number of queues.
>>> + * Frontends that are aware of this feature and wish to use it can write the
>>> + * key "multi-queue-num-queues", set to the number they wish to use, which
>>> + * must be greater than zero, and no more than the value reported by the backend
>>> + * in "multi-queue-max-queues".
>>> + *
>>> + * For frontends requesting just one queue, the usual event-channel and
>>> + * ring-ref keys are written as before, simplifying the backend processing
>>> + * to avoid distinguishing between a frontend that doesn't understand the
>>> + * multi-queue feature, and one that does, but requested only one queue.
>>> + *
>>> + * Frontends requesting two or more queues must not write the toplevel
>>> + * event-channeland ring-ref keys, instead writing those keys under sub-keys
>>> + * having the name "queue-N" where N is the integer ID of the queue/ring for
>>> + * which those keys belong. Queues are indexed from zero.
>>> + * For example, a frontend with two queues must write the following set of
>>> + * queue-related keys:
>>> + *
>>> + * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2"
>>> + * /local/domain/1/device/vbd/0/queue-0 = ""
>>> + * /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref>"
>>> + * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn>"
>>> + * /local/domain/1/device/vbd/0/queue-1 = ""
>>> + * /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref>"
>>> + * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn>"
>>
>> AFAICT, it's impossible by design to use multiple queues together with
>> multipage rings, is that right?
>>
> 
> As far as I can tell, these two features are not inherently coupled.
> Whether you want to make (by design) them coupled together or not is
> another matter. :-)

I haven't looked at the implementation yet, but some mention of whether
multipage-rings are allowed with multiqueue would be good. For example
if both can indeed be used in conjunction I would mention:

If multi-page rings are also used, the format of the grant references
will be:

/local/domain/1/device/vbd/0/queue-0/ring-ref0 = "<ring-ref0>"
/local/domain/1/device/vbd/0/queue-0/ring-ref1 = "<ring-ref1>"
/local/domain/1/device/vbd/0/queue-0/ring-ref2 = "<ring-ref2>"
[...]

Roger.

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#1238705 — Re: [Xen-devel] [PATCH v3 2/9] xen-block: add document for mutli hardware queues/rings

FromBob Liu <bob.liu@oracle.com>
Date2015-10-03 02:00 +0200
SubjectRe: [Xen-devel] [PATCH v3 2/9] xen-block: add document for mutli hardware queues/rings
Message-ID<qfip4-1IO-11@gated-at.bofh.it>
In reply to#1238395
On 10/03/2015 12:22 AM, Roger Pau Monné wrote:
> El 02/10/15 a les 18.12, Wei Liu ha escrit:
>> On Fri, Oct 02, 2015 at 06:04:35PM +0200, Roger Pau Monné wrote:
>>> El 05/09/15 a les 14.39, Bob Liu ha escrit:
>>>> Document multi queues/rings of xen-block.
>>>>
>>>> Signed-off-by: Bob Liu <bob.liu@oracle.com>
>>>
>>> As said by Konrad, you should send this against the Xen public headers
>>> also (or even before). I have a comment below.
>>>

Sure, I'll do that and also rebase this series after get more comments.

>>>> ---
>>>>  include/xen/interface/io/blkif.h |   32 ++++++++++++++++++++++++++++++++
>>>>  1 file changed, 32 insertions(+)
>>>>
>>>> diff --git a/include/xen/interface/io/blkif.h b/include/xen/interface/io/blkif.h
>>>> index c33e1c4..b453b70 100644
>>>> --- a/include/xen/interface/io/blkif.h
>>>> +++ b/include/xen/interface/io/blkif.h
>>>> @@ -28,6 +28,38 @@ typedef uint16_t blkif_vdev_t;
>>>>  typedef uint64_t blkif_sector_t;
>>>>  
>>>>  /*
>>>> + * Multiple hardware queues/rings:
>>>> + * If supported, the backend will write the key "multi-queue-max-queues" to
>>>> + * the directory for that vbd, and set its value to the maximum supported
>>>> + * number of queues.
>>>> + * Frontends that are aware of this feature and wish to use it can write the
>>>> + * key "multi-queue-num-queues", set to the number they wish to use, which
>>>> + * must be greater than zero, and no more than the value reported by the backend
>>>> + * in "multi-queue-max-queues".
>>>> + *
>>>> + * For frontends requesting just one queue, the usual event-channel and
>>>> + * ring-ref keys are written as before, simplifying the backend processing
>>>> + * to avoid distinguishing between a frontend that doesn't understand the
>>>> + * multi-queue feature, and one that does, but requested only one queue.
>>>> + *
>>>> + * Frontends requesting two or more queues must not write the toplevel
>>>> + * event-channeland ring-ref keys, instead writing those keys under sub-keys
>>>> + * having the name "queue-N" where N is the integer ID of the queue/ring for
>>>> + * which those keys belong. Queues are indexed from zero.
>>>> + * For example, a frontend with two queues must write the following set of
>>>> + * queue-related keys:
>>>> + *
>>>> + * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2"
>>>> + * /local/domain/1/device/vbd/0/queue-0 = ""
>>>> + * /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref>"
>>>> + * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn>"
>>>> + * /local/domain/1/device/vbd/0/queue-1 = ""
>>>> + * /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref>"
>>>> + * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn>"
>>>
>>> AFAICT, it's impossible by design to use multiple queues together with
>>> multipage rings, is that right?
>>>
>>
>> As far as I can tell, these two features are not inherently coupled.
>> Whether you want to make (by design) them coupled together or not is
>> another matter. :-)
> 
> I haven't looked at the implementation yet, but some mention of whether
> multipage-rings are allowed with multiqueue would be good. For example
> if both can indeed be used in conjunction I would mention:
> 
> If multi-page rings are also used, the format of the grant references
> will be:
> 
> /local/domain/1/device/vbd/0/queue-0/ring-ref0 = "<ring-ref0>"
> /local/domain/1/device/vbd/0/queue-0/ring-ref1 = "<ring-ref1>"
> /local/domain/1/device/vbd/0/queue-0/ring-ref2 = "<ring-ref2>"
> [...]
> 

True, and this is already supported. I'll update the document next version.

-- 
Regards,
-Bob
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