Date: Wed, 25 Jul 2012 07:48:57 -0700 From: Adrian Chadd <adrian@freebsd.org> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: current@freebsd.org Subject: Re: RFC: use EM_LEGACY_IRQ in if_lem.c ? Message-ID: <CAJ-VmokG-%2BkjaOC2g2uvVX5z4eBtry_-L8nMFaOPBan9SSzyYQ@mail.gmail.com> In-Reply-To: <20120724202019.GA22927@onelab2.iet.unipi.it> References: <20120724202019.GA22927@onelab2.iet.unipi.it>
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On 24 July 2012 13:20, Luigi Rizzo <rizzo@iet.unipi.it> wrote:
> if_lem.c ("lem", one of the e1000 drivers) has 2 possible interrupt modes:
> EM_LEGACY_IRQ uses the standard dispatch mechanism, whereas
> FAST_INTR has a custom handler that signals a taskqueue to do the job.
>
> I have no idea which actual hardware uses it (all of my Intel 1G
> cards use either "em" or "igb"), but "lem" is the driver used in
> qemu, and there the EM_LEGACY_IRQ gives approx 10% higher packet
> rates than the other.
>
> Any objections if i change the default to EM_LEGACY_IRQ ?
I suggest doing some digging to understand why. I bet we all know the
answer, but it would be nice to have it documented and investigated. I
bet em(4) isn't the only device that would benefit from this?
2c,
Adrian
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