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TCP/IP support for Intel I/OAT hardware

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1.  Introduction - TCP/IP support for Intel I/OAT hardware

Author: Bruce.Curtis at Sun.COM

Date: 04/11/2008

All new Sun Intel based platforms have Intel I/OAT (I/O Acceleration
Technology) hardware.

The first such hardware is an on-systemboard asynchronous DMA engine
code named Crystal Beach.

Through a set of RFEs Solaris will use this hardware to implement
TCP receive side zero CPU copy via a socket.

This is a transparent implementation, i.e. no user-land application
changes are required. No new APIs are introduced nor any changes to
existing APIs.

2. Type of Release - Patch

This is a patch as this new feature is targeting an S10 update.

3. Project Dependencies - None

This new feature doesn't depend on any other project nor does
any other project depend on it.

4. Project Architecture

The new feature is implemented as specified in 4 RFEs:

6582335 TCP/IP receive-side zero CPU copy for support
of Intel I/OAT hardware

6582330 sodirect - socket direct, for support of Intel
I/OAT hardware

6582323 uioa - uio asynchronous, for support of Intel
I/OAT hardware

6567008 driver for intel ioat v1 & v2 DMA engine needed

Such that a new device driver "ioat" interfaces to the on-board
I/OAT asynchronous DMA chip, the pseudo driver "dcopy" interfaces
to the "ioat" driver, the uioa (uioa asynchronous) extensions to
uio (user i/o) interfaces to dcopy, and lastly sockfs and tcp are
modified to setup and use sodirect (socket direct) and uioa when
a socket read()/recv() system call is made and I/OAT hardware is
present and the user buffer is of sufficent size.

Then, TCP payload data copy is accomplished via a DMA by the
NIC (as it is for non I/OAT) into a kernel mblk_t's dblk_t data
buffer then early in TCP payload processing a 2nd DMA is
started from the dblk_t data buffer to the user-land buffer
specified and the dblk_t is marked as such.

The mblk_t is processed by the network stack framework as
usual but before the read()/recv() returns sockfs checks for
the I/OAT DMA completion.

5. Public Interfaces - SUNWdcopy, sys/sodirect.h

Package contains the "ioat" device driver and "dcopy" pseudo
driver.

A new include file "sys/sodirect.h" is added to the SUNWhea
package as it is included by "sys/sonode.h" and "sys/uio.h".

6. Interface Specification

The commitment level for "SUNWdcopy" and the driver names
"ioat" and "dcopy" are: stable

The include file "sys/sodirect.h", and any interfaces contained
there in, are: project private


7. Resources and Schedule
7.4. Steering Committee requested information
7.4.1. Consolidation C-team Name:
ON
7.5. ARC review type: Automatic
7.6. ARC Exposure: open

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