site_archiver@lists.apple.com Delivered-To: darwin-dev@lists.apple.com Terry Lambert writes:

On Sep 4, 2007, at 6:09 AM, Andrew Gallatin wrote:

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The *NIC* has looked at it, and can easily hash different connections to several MSI-X interrupt handlers, which are then each bound to different CPUs (or groups of CPUs).

I am told we support this (Message Signalled Interrupts) for the latest Intel OS releases, and that it is in fact the preferred method of interrupt delivery these days, for hardware capable of supporting it. I wasn't able to find the tech note, which is supposed to have been published already, according to the author, so you might want to contact DTS.

MSI is different from MSI-X. I figured out how to use MSI from the headers / source last winter, but AFAIK, darwin/macosx does not yet support MSI-X, which is required to have multiple interrupt vectors per device which are bound to different CPUs. In fact, I think MSI-X and support for multiple interrupt handlers per device is in direct conflict with the IOKit workloop design concept. If all the interrupt vectors activated the same workloop, MSI-X would be pointless. Having all the vectors serialized into a single workloop would loose any hope parallelism. And I think that a single driver is not allowed to have multiple workloops.

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Microsoft has though. It is called "receive side scaling" or RSS. The cleverness is that the NIC and the host has the connections to the same (sets of) CPUs.

Even in the absence of RSS, multiple MSI-X interrupt handlers, etc, you can get a decent approximation of a crystal ball by having the ability to statically bind a single interrupt and a set of hot threads to set of CPUs. Eg, the administrator is the crystal ball.

It's a little more complex than that when you throw power management into the Mix, but it's more or less up to the driver author to do the RSS implementation on top of MSI.

Not MSI, MSI-X, which is AFAIK, missing in darwin/macosx.

Of course, this requires relatively smart hardware to take full

I think all 10GbE NICs on the market today can do this, as well as some 1GbE NICs.

advantage of it (e.g. Microsoft want segment offloading in the cards, plus scatter/gather, etc.).

These features are supported in nearly every OS besides MacOSX. Heck, you can find TSO support on almost every 1Gbe NIC (including the Intel NICs built into Intel Apple hardware). I opened an enhancement request for TSO over 2 years ago (4131204). Drew _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.appl... This email sent to site_archiver@lists.apple.com