Re: [RFC][PATCH 000 of 3] MD Acceleration and the ADMA interface: Introduction

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Dan Williams wrote:
This patch set was originally posted to linux-raid, Neil suggested that
I send to linux-kernel as well:

Per the discussion in this thread (
t=112603120100004&r=1&w=2) these patches implement the first phase of MD
acceleration, pre-emptible xor.  To date these patches only cover raid5
calls to compute_parity for read/modify and reconstruct writes.  The
plan is to expand this to cover raid5 check parity, raid5 compute block,
as well as the raid6 equivalents.

The ADMA (Asynchronous / Application Specific DMA) interface is proposed
as a cross platform mechanism for supporting system CPU offload engines.
The goal is to provide a unified asynchronous interface to support
memory copies, block xor, block pattern setting, block compare, CRC
calculation, cryptography etc.  The ADMA interface should support a PIO
fallback mode allowing a given ADMA engine implementation to use the
system CPU for operations without a hardware accelerated backend.  In
other words a client coded to the ADMA interface transparently receives
hardware acceleration for its operations depending on the features of
the underlying platform.
Here are some other things out there worth considering:

* SCSI XOR commands

* Figuring out how to support Promise SX4 (e.g. device offload), which is a chip with integrated XOR engine and attached DIMM. RAID1 and RAID5 are best implemented on-card, but the Linux driver is responsible for implementing all on-card actions, not a firmware.

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