Re: [Qemu-devel] [PATCH v6] e1000: add interrupt mitigation support

[Stefan Hajnoczi <stefanha@redhat.com>]

On Fri, Aug 02, 2013 at 06:30:52PM +0200, Vincenzo Maffione wrote:
> This patch partially implements the e1000 interrupt mitigation mechanisms.
> Using a single QEMUTimer, it emulates the ITR register (which is the newer
> mitigation register, recommended by Intel) and approximately emulates
> RADV and TADV registers. TIDV and RDTR register functionalities are not
> emulated (RDTR is only used to validate RADV, according to the e1000 specs).
> 
> RADV, TADV, TIDV and RDTR registers make up the older e1000 mitigation
> mechanism and would need a timer each to be completely emulated. However,
> a single timer has been used in order to reach a good compromise between
> emulation accuracy and simplicity/efficiency.
> 
> The implemented mechanism can be enabled/disabled specifying the command
> line e1000-specific boolean parameter "mitigation", e.g.
> 
>     qemu-system-x86_64 -device e1000,mitigation=on,... ...
> 
> For more information, see the Software developer's manual at
> http://download.intel.com/design/network/manuals/8254x_GBe_SDM.pdf.
> 
> Interrupt mitigation boosts performance when the guest suffers from
> an high interrupt rate (i.e. receiving short UDP packets at high packet
> rate). For some numerical results see the following link
> http://info.iet.unipi.it/~luigi/papers/20130520-rizzo-vm.pdf
> 
> Signed-off-by: Vincenzo Maffione <v.maffione@gmail.com>
> ---
> Added pc-*-1.7 machines (default machine moved to pc-i440fx-1.7).
> 
>  hw/i386/pc_piix.c    |  18 ++++++-
>  hw/i386/pc_q35.c     |  16 ++++++-
>  hw/net/e1000.c       | 131 +++++++++++++++++++++++++++++++++++++++++++++++++--
>  include/hw/i386/pc.h |   8 ++++
>  4 files changed, 167 insertions(+), 6 deletions(-)

I will merge this into my net tree soon but I'd like to wait for
Andreas' review to make sure he's comfortable with the machine type
changes too.

Stefan