Notice

This document is for a development version of Ceph.

QAT Acceleration for Encryption and Compression

Intel QAT (QuickAssist Technology) can provide extended accelerated encryption and compression services by offloading the actual encryption and compression request(s) to the hardware QuickAssist accelerators, which are more efficient in terms of cost and power than general purpose CPUs for those specific compute-intensive workloads.

See QAT Support for Compression and QAT based Encryption for RGW.

QAT in the Software Stack

Application developers can access QuickAssist features through the QAT API. The QAT API is the top-level API for QuickAssist technology, and enables easy interfacing between the customer application and the QuickAssist acceleration driver.

The QAT API accesses the QuickAssist driver, which in turn drives the QuickAssist Accelerator hardware. The QuickAssist driver is responsible for exposing the acceleration services to the application software.

A user can write directly to the QAT API, or the use of QAT can be done via frameworks that have been enabled by others including Intel (for example, zlib*, OpenSSL* libcrypto*, and the Linux* Kernel Crypto Framework).

QAT Environment Setup

  1. QuickAssist Accelerator hardware is necessary to make use of accelerated encryption and compression services. And QAT driver in kernel space have to be loaded to drive the hardware.

The driver package can be downloaded from Intel Quickassist Technology.

  1. The implementation for QAT based encryption is directly base on QAT API which is included the driver package. But QAT support for compression depends on QATzip project, which is a user space library which builds on top of the QAT API. Currently, QATzip speeds up gzip compression and decompression at the time of writing.

See QATzip.

Implementation

  1. QAT based Encryption for RGW

OpenSSL support for RGW encryption has been merged into Ceph, and Intel also provides one QAT Engine for OpenSSL. So, theoretically speaking, QAT based encryption in Ceph can be directly supported through OpenSSl+QAT Engine.

But the QAT Engine for OpenSSL currently supports chained operations only, and so Ceph will not be able to utilize QAT hardware feature for crypto operations based on OpenSSL crypto plugin. As a result, one QAT plugin based on native QAT API is added into crypto framework.

  1. QAT Support for Compression

As mentioned above, QAT support for compression is based on QATzip library in user space, which is designed to take full advantage of the performance provided by QuickAssist Technology. Unlike QAT based encryption, QAT based compression is supported through a tool class for QAT acceleration rather than a compressor plugin. The common tool class can transparently accelerate the existing compression types, but only zlib compressor can be supported at the time of writing. So user is allowed to use it to speed up zlib compressor as long as the QAT hardware is available and QAT is capable to handle it.

Configuration

  1. Prerequisites

    Make sure the QAT driver with version v1.7.L.4.14.0 or higher has been installed. Remember to set an environment variable “ICP_ROOT” for your QAT driver package root directory.

    To enable the QAT based encryption and compression, user needs to modify the QAT configuration files. For example, for Intel QuickAssist Adapter 8970 product, revise c6xx_dev0/1/2.conf in the directory /etc/ and keep them the same, e.g.:

    #...
    # User Process Instance Section
    ##############################################
    [CEPH]
    NumberCyInstances = 1
    NumberDcInstances = 1
    NumProcesses = 8
    LimitDevAccess = 1
    # Crypto - User instance #0
    Cy0Name = "SSL0"
    Cy0IsPolled = 1
    # List of core affinities
    Cy0CoreAffinity = 0
    
    # Data Compression - User instance #0
    Dc0Name = "Dc0"
    Dc0IsPolled = 1
    # List of core affinities
    Dc0CoreAffinity = 0
    
  2. QAT based Encryption for RGW

    The CMake option WITH_QAT=ON must be configured. If you build Ceph from source code (see: Build Ceph), navigate to your cloned Ceph repository and execute the following:

    cd ceph
    ./do_cmake.sh -DWITH_QAT=ON
    cd build
    ininja
    

    Note

    The section name of the QAT configuration files must be CEPH since the section name is set as “CEPH” in Ceph crypto source code.

    Then, edit the Ceph configuration file to make use of QAT based crypto plugin:

    plugin crypto accelerator = crypto_qat
    
  3. QAT Support for Compression

    Before starting, make sure both QAT driver and QATzip have been installed. Besides “ICP_ROOT”, remember to set the environment variable “QZ_ROOT” for the root directory of your QATzip source tree.

    The following CMake options have to be configured to trigger QAT based compression when building Ceph:

    ./do_cmake.sh -DWITH_QAT=ON -DWITH_QATZIP=ON
    

    Then, set an environment variable to clarify the section name of User Process Instance Section in QAT configuration files, e.g.:

    export QAT_SECTION_NAME=CEPH
    

    Next, edit the Ceph configuration file to enable QAT support for compression:

    qat compressor enabled=true