[libvirt] [PATCH 3/4] domain_conf: Add support for iothreads in disk definition
Ján Tomko
jtomko at redhat.com
Tue Aug 26 17:51:24 UTC 2014
On 08/26/2014 06:42 PM, John Ferlan wrote:
>
>
> On 08/26/2014 12:04 PM, Ján Tomko wrote:
>> On 08/26/2014 02:38 AM, John Ferlan wrote:
>>> Add a new disk "driver" attribute "iothread" to be parsed as the thread
>>> number for the disk to use. In order to more easily facilitate the usage
>>> and configuration of the iothread, a "zero" for the attribute indicates
>>> iothreads are not supported for the device and a positive value indicates
>>> the specific thread to try and use.
>>>
>>> Signed-off-by: John Ferlan <jferlan at redhat.com>
>>> ---
>>> docs/formatdomain.html.in | 8 ++++++++
>>> docs/schemas/domaincommon.rng | 13 +++++++++++++
>>> src/conf/domain_conf.c | 24 +++++++++++++++++++++++-
>>> src/conf/domain_conf.h | 2 ++
>>> 4 files changed, 46 insertions(+), 1 deletion(-)
>>>
>>
>>> @@ -11968,6 +11980,14 @@ virDomainDefParseXML(xmlDocPtr xml,
>>> goto error;
>>> }
>>> def->iothreads = count;
>>> +
>>> + /* Create a bitmap for inuse threads - noting that entries are
>>> + * numbered 1..def->iothreads since 0 (zero) iothreads means
>>> + * nothing and assigning a disk to an IOThread requires at least a
>>> + * thread# > 0 since a zero would indicate no IOThread for the disk
>>> + */
>>> + if (!(def->iothreadmap = virBitmapNew(def->iothreads+1)))
>>> + goto error;
>>> }
>>
>> Do you plan to do multiple disks on a single iothread in the followup patches?
>> Or is that a configuration that doesn't make sense?
>>
>
> I would say it doesn't make sense and from the bz I have the comment is
> "2. 1 IOThread per device" (bz 1101574 if you care to read although it's
> mostly private comments though which is why I didn't put it in the patches).
>
I was wondering what's up with all the private comments.
Hopefully I can share the bit you're quoting:
There are basically two ways to use IOThreads:
1. 1 or maybe 2 IOThreads per host CPU
2. 1 IOThread per device
For usage 1), can you just add some <iothreads> to the domain XML and they
will automatically be used, or do you need to 'bind' the specific disk devices
to them?
Jan
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