Re: [Qemu-devel] MSI interrupt support with vioscsi.c miniport driver

[Vadim Rozenfeld]

On Thu, 2014-10-30 at 18:28 +0800, Wangting (Kathy) wrote:
> 
> On 2014-10-30 16:48, Vadim Rozenfeld wrote:
> > On Thu, 2014-10-30 at 14:54 +0800, Wangting (Kathy) wrote:
> >>> On Tue, 2014-02-18 at 13:11 -0800, Nicholas A. Bellinger wrote:
> >>>> On Tue, 2014-02-18 at 13:00 -0800, Nicholas A. Bellinger wrote:
> >>>>> On Mon, 2014-02-10 at 11:05 -0800, Nicholas A. Bellinger wrote:
> >>>>>
> >>>>> <SNIP>
> >>>>>
> >>>>>>>>> Hi Yan,
> >>>>>>>>>
> >>>>>>>>> So recently I've been doing some KVM guest performance comparisons
> >>>>>>>>> between the scsi-mq prototype using virtio-scsi + vhost-scsi, and
> >>>>>>>>> Windows Server 2012 with vioscsi.sys (virtio-win-0.1-74.iso) +
> >>>>>>>>> vhost-scsi using PCIe flash backend devices.
> >>>>>>>>>
> >>>>>>>>> I've noticed that small block random performance for the MSFT guest 
> >>>>>>>>> is
> >>>>>>>>> at around ~80K IOPs with multiple vioscsi LUNs + adapters, which 
> >>>>>>>>> ends up
> >>>>>>>>> being well below what the Linux guest with scsi-mq + virtio-scsi is
> >>>>>>>>> capable of (~500K).
> >>>>>>>>>
> >>>>>>>>> After searching through the various vioscsi registry settings, it
> >>>>>>>>> appears that MSIEnabled is being explicitly disabled (0x00000000), 
> >>>>>>>>> that
> >>>>>>>>> is different from what vioscsi.inx is currently defining:
> >>>>>>>>>
> >>>>>>>>> [pnpsafe_pci_addreg_msix]
> >>>>>>>>> HKR, "Interrupt Management",, 0x00000010
> >>>>>>>>> HKR, "Interrupt Management\MessageSignaledInterruptProperties",, 
> >>>>>>>>> 0x00000010
> >>>>>>>>> HKR, "Interrupt Management\MessageSignaledInterruptProperties", 
> >>>>>>>>> MSISupported, 0x00010001, 0
> >>>>>>>>> HKR, "Interrupt Management\MessageSignaledInterruptProperties", 
> >>>>>>>>> MessageNumberLimit, 0x00010001, 4
> >>>>>>>>>
> >>>>>>>>> Looking deeper at vioscsi.c code, I've noticed that MSI_SUPPORTED=0 
> >>>>>>>>> is
> >>>>>>>>> explicitly disabled at build time in SOURCES + vioscsi.vcxproj, as 
> >>>>>>>>> well
> >>>>>>>>> as VioScsiFindAdapter() code always ends setting msix_enabled = 
> >>>>>>>>> FALSE
> >>>>>>>>> here, regardless of MSI_SUPPORTED:
> >>>>>>>>>
> >>>>>>>>>  
> >>>>>>>>> https://github.com/YanVugenfirer/kvm-guest-drivers-windows/blob/master/vioscsi/vioscsi.c#L340
> >>>>>>>>>
> >>>>>>>>> Also looking at virtio_stor.c for the raw block driver, 
> >>>>>>>>> MSI_SUPPORTED=1
> >>>>>>>>> appears to be the default setting for the driver included in the 
> >>>>>>>>> offical
> >>>>>>>>> virtio-win iso builds, right..?
> >>>>>>>>>
> >>>>>>>>> Sooo, I'd like to try enabling MSI_SUPPORTED=1 in a test vioscsi.sys
> >>>>>>>>> build of my own, but before going down the WDK development rabbit 
> >>>>>>>>> whole,
> >>>>>>>>> I'd like to better understand why you've explicitly disabled this 
> >>>>>>>>> logic
> >>>>>>>>> within vioscsi.c code to start..?
> >>>>>>>>>
> >>>>>>>>> Is there anything that needs to be addressed / carried over from
> >>>>>>>>> virtio_stor.c in order to get MSI_SUPPORTED=1 to work with vioscsi.c
> >>>>>>>>> miniport code..?
> >>>>>>>
> >>>>>>> Hi Nicholas,
> >>>>>>>
> >>>>>>> I was thinking about enabling MSI in RHEL 6.6 (build 74) but for some
> >>>>>>> reasons decided to keep it disabled until adding mq support.
> >>>>>>>
> >>>>>>>
> >>>>>>> You definitely should be able to turn on MSI_SUPPORTED, rebuild the
> >>>>>>> driver, and switch MSISupported to 1 to make vioscsi driver working in
> >>>>>>> MSI mode.
> >>>>>>>    
> >>>>>>
> >>>>>> Thanks for the quick response.  We'll give MSI_SUPPORTED=1 a shot over
> >>>>>> the next days with a test build on Server 2012 / Server 2008 R2 and see
> >>>>>> how things go..
> >>>>>>
> >>>>>
> >>>>> Just a quick update on progress.
> >>>>>
> >>>>> I've been able to successfully build + load a unsigned vioscsi.sys
> >>>>> driver on Server 2012 with WDK 8.0.
> >>>>>
> >>>>> Running with MSI_SUPPORTED=1 against vhost-scsi results in a significant
> >>>>> performance and efficiency gain, on the order of 100K to 225K IOPs for
> >>>>> 4K block random I/O workload, depending on read/write mix.
> >>>>>
> >>>>
> >>>> One other performance related question..
> >>>>
> >>>> In vioscsi.c:VioScsiFindAdapter() code, the default setting for
> >>>> adaptExt->queue_depth ends up getting set to 32 (pageNum / 4) when
> >>>> indirect mode is enabled in the following bits:
> >>>>
> >>>>     if(adaptExt->indirect) {
> >>>>         adaptExt->queue_depth = max(2, (pageNum / 4));
> >>>>     } else {
> >>>>         adaptExt->queue_depth = pageNum / 
> >>>> ConfigInfo->NumberOfPhysicalBreaks 
> >>>> - 1;
> >>>>     }
> >>>>
> >>>> Looking at viostor/virtio_stor.c:VirtIoFindAdapter() code, the default
> >>>> setting for ->queue_depth appears to be 128 (pageNum):
> >>>>
> >>>> #if (INDIRECT_SUPPORTED)
> >>>>     if(!adaptExt->dump_mode) {
> >>>>         adaptExt->indirect = CHECKBIT(adaptExt->features, 
> >>>> VIRTIO_RING_F_INDIRECT_DESC);
> >>>>     }
> >>>>     if(adaptExt->indirect) {
> >>>>         adaptExt->queue_depth = pageNum;
> >>>>     }
> >>>> #else
> >>>>     adaptExt->indirect = 0;
> >>>> #endif
> >>>>
> >>>> Is there a reason for the lower queue_depth for vioscsi vs. viostor..?
> >>>
> >>> It's a horrible work around for the following bug:
> >>> https://bugzilla.redhat.com/show_bug.cgi?id=1013443
> >>>
> >>> I'm going to remove it as soon as found better solution for it.
> >>>
> >>> Best regards,
> >>> Vadim.
> >>>
> >>>
> >> Hi Vadim,
> >>
> >> I have found that Bug 1013443 has been closed with a
> >> resolution of ERRATA.
> >>
> >> The windows device queue must be between 20 and 254
> >> for StorPortSetDeviceQueueDepth to succeed.
> >>
> >> So I have the question that why queue_depth can not be
> >> set to pageNum(128)?
> > 
> > It will create a problem on multi disk setup, when several 
> > disks are attached to the same virtio-scsi pci controller.
> > Adding some sort of manually managed SRBs queue for storing and
> > resubmitting pending requests can solve this problem.
> > 
> > Cheers,
> > Vadim.
> > 
> 
> Is there a patch for it?

Yes, not committed and not fully tested yet. Please, find it attached.

Best,
Vadim.

> 
> >>
> >> Best wishes,
> >> Ting Wang
> >>
> >>>>
> >>>> How about using min(adaptExt->scsi_config.cmd_per_lun, pageNum) 
> >>>> instead..?
> >>>>
> >>>> Thanks!
> >>>>
> >>>> -nab
> >>>>
> >>>>
> >>
> >>
> > 
> > 
> > 
> > .
> > 
> 
>

0001-queue-depth254.patch
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