[Qemu-devel] Re: [PATCH v7 0/4] piix_pci: optimize irq data path

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Apr 01, 2011 at 08:43:20PM +0900, Isaku Yamahata wrote:
> Here is v7 which are rebased to pci branch.
> 
> I tested this patch series as follows. please see the commit message
> for details.
> - 3/4 piix_pci: optimize set irq path
>   Run linux as guest with 4 e1000 emulated devices.
>   And confirmed that each PIRQ[A-D] are able to assert interrupts.
> - 4/4 piix_pci: load path clean up
>   Run linux as guest with one e1000 emulated device.
>   savevm/loadvm guest with runing ping -f in guest.
> 
> To be honest, the patch, "4/4 piix_pci: load path clean up", needs more
> extensive tests. For example live migration and stress test.
> But for now I don't have plan to further testing in near future. Sorry.
> So please feel free to pick or drop the last patch.

Applied, I will hit it with autotest.

> patch description:
> This patch series optimizes irq data path of piix_pci.
> So far piix3 tracks each pirq level and checks whether a given pic pins is
> asserted by seeing if each pirq is mapped into the pic pin.
> This is independent on irq routing, but data path is on slow path.
> 
> Given that irq routing is rarely changed and asserting pic pins is on
> data path, the path that asserts pic pins should be optimized and
> chainging irq routing should be on slow path.
> The new behavior with this patch series is to use bitmap which is addressed
> by pirq and pic pins with a given irq routing.
> When pirq is asserted, the bitmap is set and see if the pic pins is
> asserted by checking the bitmaps.
> When irq routing is changed, rebuild the bitmap and re-assert pic pins.
> 
> Changes v6 -> v7:
> - rebased to pci branch
> - added how to test to the commit message
> 
> Changes v5 -> v6:
> - fixed piix3_set_irq_pic()
> 
> Changes v4 -> v5:
> - typo
> 
> Changes v3 -> v4:
> - use pirq, pci_intx instead of irq_num in piix_pci.c
> - use symbolic constant PIC_NUM_PINS
> - introduced new patch 4/4 which cleans up a bit.
> 
> Changes v2 -> v3:
> - s/dummy_for_save_load_compat/pci_irq_levels_vmstate/g
> - move down unused member of pci_irq_levels_vmstate in the structure
>   for cache efficiency
> 
> Changes v1 -> v2:
> - addressed review comments.
> 
> Isaku Yamahata (4):
>   pci: add accessor function to get irq levels
>   piix_pci: eliminate PIIX3State::pci_irq_levels
>   piix_pci: optimize set irq path
>   piix_pci: load path clean up
> 
>  hw/pci.c      |    7 +++
>  hw/pci.h      |    1 +
>  hw/piix_pci.c |  129 ++++++++++++++++++++++++++++++++++++++++++++++-----------
>  3 files changed, 112 insertions(+), 25 deletions(-)