Re: [Qemu-devel] [PATCH v5 1/2] e1000: add interrupt mitigation support

["Andreas Färber" <afaerber@suse.de>]

Am 31.07.2013 10:13, schrieb Vincenzo Maffione:
> 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 "mit", e.g.

"mitigation" in example and property definitions below.

> 
>     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>
> ---
>  hw/net/e1000.c | 131 +++++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 128 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/net/e1000.c b/hw/net/e1000.c
> index fdb1f89..32014c2 100644
> --- a/hw/net/e1000.c
> +++ b/hw/net/e1000.c
[...]
> @@ -1385,6 +1508,8 @@ static Property e1000_properties[] = {
>      DEFINE_NIC_PROPERTIES(E1000State, conf),
>      DEFINE_PROP_BIT("autonegotiation", E1000State,
>                      compat_flags, E1000_FLAG_AUTONEG_BIT, true),
> +    DEFINE_PROP_BIT("mitigation", E1000State,
> +                    compat_flags, E1000_FLAG_MIT_BIT, true),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  

Regards,
Andreas

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