On 04/19/2013 04:32 AM, Osier Yang wrote:
On 18/04/13 19:59, Laine Stump wrote:
On 04/18/2013 07:27 AM, Osier Yang wrote:
On 18/04/13 19:16, Laine Stump wrote:
On 04/18/2013 11:05 AM, Osier Yang wrote:
On 18/04/13 17:00, Martin Kletzander wrote: > On 04/18/2013 10:54 AM, Osier Yang wrote: >> On 18/04/13 16:42, Martin Kletzander wrote: >>> On 04/18/2013 06:36 AM, Laine Stump wrote: >>>> The rng schema for <controller> had been non-specific about >>>> which >>>> types of controllers allowed which models, and also allowed the >>>> num_queues attribute (since that hasn't been released yet, >>>> should we >>>> rename it to "numQueues"?) >>> Since there's still time (the commit with that is >>> v1.0.4-65-gd4bf0a9), I >>> think we should rename it ASAP since we are using camelCase for >>> all the >>> attribute names. >>> >>> Apart from that, the RNG with this patch is precise according to >>> the >>> documentation, so ACK. I'll try to send the numQueues patch >>> to see >>> what >>> others think. >> I guess you mean multiple queues support for virtio network? >> Regardless of which style we will use finally, FYI, >> "num_queues" is >> used for disk.. Personally I'm fine with either, because we >> already >> use both across. >> > Yes, I meant the virtio-scsi num_queues. As we're trying not to > use > underscores in XML, I hope we can still switch it. I haven't > found any > other num_queues anywhere in the code. Could you point me to the > commit > that uses that? I'm sending the previously discussed patch in the > meantime. > Except the virtio-scsi num_queues, there is no other tag for multiple queue yet, we will need a patch to support multiple queue for the network, but it's not committed yet.
It's fine to convert it now, 1.0.5 is not released yet. But is it deserved to do, we already have many tags with underscore, which can't be changed for back-compat.
I believe those attributes [1] were created by mistake, and kept only because of backward compatibility. I'm trying to be open-minded, though, so I'm not forcing my patch in, but seeing it just as a proposal. Others may have different opinions and I'm willing to discuss that. My first feeling, though, was that we should try to keep the same policy for as many of them as possible. OTOH, I've mistaken the underscore with a hyphen when I remembered what Daniel told me about attributes [2]. I had recalled DV saying something about underscores in the names a long time ago, and I recently asked about underscore vs. camelCase, and danpb said the same thing. (Personally I don't have a preference one way or
On 04/18/2013 05:41 AM, Martin Kletzander wrote: the other, but if we really are trying to avoid them, now is our chance). I'm fine with either keeping it or changing num_queues. For long term consistence, I agreed with having a consistent naming style is nice.
In the meantime, in other device types, we've tried to keep backend details like this pushed into a <driver> subelement when possible, to avoid polluting the main element (e.g. see the <driver> subelement of <interface>). Is it worth putting this numQueues attribute in a <driver> subelement too? Or am I just playing XML God? Not sure if you mean the upcoming numQueues for interface. But for the existing num_queues, it's for the virtio-scsi controller, putting it in <driver> doesn't reflect the purpose.
But isn't it a backend implementation detail of the specific SCSI controller? In <interface> and <disk>, information that is specific to a particular backend (and isn't generally applicable to that type of device) is in the <driver> subelement.
This is the QEMU command line for a virtio-scsi disk: ("-device virtio-scsi-pci" is mapped to virtio-scsi controller in libvirt XML, with num_queues set): <...> -device virtio-scsi-pci,id=scsi0,num_queues=8,bus=pci.0,addr=0x3 \ -usb \ -drive file=/dev/HostVG/QEMUGuest1,if=none,id=drive-scsi0-0-0-0 \ -device scsi-disk,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0 \ </...>
And this is the QEMU command line for a virtio disk (with event_idx set): <...> -drive file=/var/lib/libvirt/images/f14.img,if=none,id=drive-virtio-disk0 \ -device virtio-blk-pci,event_idx=on,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0 \ </...>
This is the properties the QEMU device "scsi-disk" supports:
% ./x86_64-softmmu/qemu-system-x86_64 -device scsi-disk,? scsi-disk.drive=drive scsi-disk.logical_block_size=blocksize scsi-disk.physical_block_size=blocksize scsi-disk.min_io_size=uint16 scsi-disk.opt_io_size=uint32 scsi-disk.bootindex=int32 scsi-disk.discard_granularity=uint32 scsi-disk.ver=string scsi-disk.serial=string scsi-disk.vendor=string scsi-disk.product=string scsi-disk.removable=on/off scsi-disk.dpofua=on/off scsi-disk.wwn=hex64 scsi-disk.channel=uint32 scsi-disk.scsi-id=uint32 scsi-disk.lun=uint32
And the properties "virtio-blk-pci" device supports:
% ./x86_64-softmmu/qemu-system-x86_64 -device virtio-blk-pci,? virtio-blk-pci.class=hex32 virtio-blk-pci.ioeventfd=on/off virtio-blk-pci.vectors=uint32 virtio-blk-pci.indirect_desc=on/off virtio-blk-pci.event_idx=on/off virtio-blk-pci.drive=drive virtio-blk-pci.logical_block_size=blocksize virtio-blk-pci.physical_block_size=blocksize virtio-blk-pci.min_io_size=uint16 virtio-blk-pci.opt_io_size=uint32 virtio-blk-pci.bootindex=int32 virtio-blk-pci.discard_granularity=uint32 virtio-blk-pci.cyls=uint32 virtio-blk-pci.heads=uint32 virtio-blk-pci.secs=uint32 virtio-blk-pci.serial=string virtio-blk-pci.config-wce=on/off virtio-blk-pci.scsi=on/off virtio-blk-pci.addr=pci-devfn virtio-blk-pci.romfile=string virtio-blk-pci.rombar=uint32 virtio-blk-pci.multifunction=on/off virtio-blk-pci.command_serr_enable=on/off
And the properties "virtio-scsi-pci" device supports:
% ./x86_64-softmmu/qemu-system-x86_64 -device virtio-scsi-pci,? virtio-scsi-pci.ioeventfd=on/off virtio-scsi-pci.vectors=uint32 virtio-scsi-pci.indirect_desc=on/off virtio-scsi-pci.event_idx=on/off virtio-scsi-pci.hotplug=on/off virtio-scsi-pci.param_change=on/off virtio-scsi-pci.num_queues=uint32 virtio-scsi-pci.max_sectors=uint32 virtio-scsi-pci.cmd_per_lun=uint32 virtio-scsi-pci.addr=pci-devfn virtio-scsi-pci.romfile=string virtio-scsi-pci.rombar=uint32 virtio-scsi-pci.multifunction=on/off virtio-scsi-pci.command_serr_enable=on/off
We can put things like "ioeventfd", "event_idx" in the <driver> subelement, is because of the QEMU device used for disk supports it. But for a virtio-scsi disk, "num_queues" is supported in a separate device "virtio-scsi-pci" instead.. That means, from libvirt p.o.v, things like "ioevent_idx" are for disk, "num_queues" is for the disk controller.
Assuming that we put "num_queues" or "numQueues" in <driver>, then we need to find out the controller for disk when building QEMU command line, and check if it's virtio-scsi model, if not, error out, otherwise tell the function to build the controller device string that "num_queues" is specified, and what its value is. Or something similar but reversely (find out the disk associated with the virtio-scsi controller, check if num_queues is specified). This might be not the exact process, but it can show putting "num_queues" in <driver> is just a straight wrong way to go...
Wait. So you're saying that num_queues is a property of the *controller* and not of the individual disk, but you've put the config option in the <disk> rather than the <controller>? Why would you do that? If it's a property of the controller, put the tuning parameter in <controller>. Otherwise, what do you do when one <disk> is configured for num_queues=10 and another disk on the same controller is configured for num_queues=2? (And even if you didn't move the config to <controller> (where it seems to me it belongs), moving to the <driver> subelement would still be appropriate - it's still a "backend-specific tuning parameter").