Re: [PATCH 0/3] Enable multiple MSI feature in pSeries

[Mike Qiu]

2013/2/4 13:56, Michael Ellerman:
> On Mon, 2013-02-04 at 11:49 +0800, Mike Qiu wrote:
> > > On Tue, 2013-01-15 at 15:38 +0800, Mike Qiu wrote:
> > > > Currently, multiple MSI feature hasn't been enabled in pSeries,
> > > > These patches try to enbale this feature.
> > > Hi Mike,
> > >
> > > > These patches have been tested by using ipr driver, and the driver patch
> > > > has been made by Wen Xiong <wenxiong@xxxxxxxxxxxxxxxxxx>:
> > > So who wrote these patches? Normally we would expect the original author
> > > to post the patches if at all possible.
> > Hi Michael
> >
> > These Multiple MSI patches were wrote by myself, you know this feature
> > has not enabled
> > and it need device driver to test whether it works suitable. So I test
> > my patches use
> > Wen Xiong's ipr patches, which has been send out to the maillinglist.
> >
> > I'm the original author :)
> Ah OK, sorry, that was more or less clear from your mail but I just
> misunderstood.
>
> > > > [PATCH 0/7] Add support for new IBM SAS controllers
> > > I would like to see the full series, including the driver enablement.
> > Yep, but the driver patches were wrote by Wen Xiong and has been send
> > out.
> OK, you mean this series?
>
> http://thread.gmane.org/gmane.linux.scsi/79639
Yes, exactly.
> > I just use her patches to test my patches. all device support Multiple
> > MSI can use my feature not only IBM SAS controllers, I also test my
> > patches use the broadcom wireless card tg3, and also works OK.
> You mean drivers/net/ethernet/broadcom/tg3.c ? I don't see where it
> calls pci_enable_msi_block() ?
Yes, I just modify the driver to support mutiple MSI.
> All devices /can/ use it, but the driver needs to be updated. Currently
> we have two drivers that do so (in Linus' tree), plus the updated IPR.
Not all devices, just the device which support the multiple MSI by hardware,
can use it
> > > > Test platform: One partition of pSeries with one cpu core(4 SMTs) and
> > > >                 RAID bus controller: IBM PCI-E IPR SAS Adapter (ASIC) in POWER7
> > > > OS version: SUSE Linux Enterprise Server 11 SP2  (ppc64) with 3.8-rc3 kernel
> > > >
> > > > IRQ 21 and 22 are assigned to the ipr device which support 2 mutiple MSI.
> > > >
> > > > The test results is shown by 'cat /proc/interrups':
> > > >            CPU0       CPU1       CPU2       CPU3
> > > > 21:          6          5          5          5      XICS Level     host1-0
> > > > 22:        817        814        816        813      XICS Level     host1-1
> > > This shows that you are correctly configuring two MSIs.
> > >
> > > But the key advantage of using multiple interrupts is to distribute load
> > > across CPUs and improve performance. So I would like to see some
> > > performance numbers that show that there is a real benefit for all the
> > > extra complexity in the code.
> > Yes, the system just has suport two MSIs. Anyway, I will try to do
> > some proformance test, to show the real benefit.
> > But actually it needs the driver to do so. As the data show above, it
> > seems there is some problems in use the interrupt, the irq 21 use few,
> > most use 22, I will discuss with the driver author to see why and if
> > she fixed, I will give out the proformance result.
> Yeah that would be good.
>
> I really dislike that we have a separate API for multi-MSI vs MSI-X, and
> pci_enable_msi_block() also pushes the contiguous power-of-2 allocation
> into the irq domain layer, which is unpleasant. So if we really must do
> multi-MSI I would like to do it differently.
Yes, but the multi-MSI must need the hardware support, it is one extend 
for MSI,
The device may sopport MSI and multiple MSI, but not support MSI-X.
for these devices, we'd better use multiple MSI to makes it more efficiency,
compare with MSI.

multi-MSI just can use no more than 32 interrupts

Thanks
> cheers

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